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Merge tag 'hole_punch_for_v5.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

Pull fs hole punching vs cache filling race fixes from Jan Kara:
 "Fix races leading to possible data corruption or stale data exposure
  in multiple filesystems when hole punching races with operations such
  as readahead.

  This is the series I was sending for the last merge window but with
  your objection fixed - now filemap_fault() has been modified to take
  invalidate_lock only when we need to create new page in the page cache
  and / or bring it uptodate"

* tag 'hole_punch_for_v5.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  filesystems/locking: fix Malformed table warning
  cifs: Fix race between hole punch and page fault
  ceph: Fix race between hole punch and page fault
  fuse: Convert to using invalidate_lock
  f2fs: Convert to using invalidate_lock
  zonefs: Convert to using invalidate_lock
  xfs: Convert double locking of MMAPLOCK to use VFS helpers
  xfs: Convert to use invalidate_lock
  xfs: Refactor xfs_isilocked()
  ext2: Convert to using invalidate_lock
  ext4: Convert to use mapping->invalidate_lock
  mm: Add functions to lock invalidate_lock for two mappings
  mm: Protect operations adding pages to page cache with invalidate_lock
  documentation: Sync file_operations members with reality
  mm: Fix comments mentioning i_mutex
This commit is contained in:
Linus Torvalds 2021-08-30 10:24:50 -07:00
parent a1ca8e7147 7882c55ef6
commit aa99f3c2b9
40 changed files with 483 additions and 361 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

79
Documentation/filesystems/locking.rst
View File

@ -271,19 +271,19 @@ prototypes::
locking rules:
All except set_page_dirty and freepage may block
====================== ======================== =========
ops PageLocked(page) i_rwsem
====================== ======================== =========
====================== ======================== ========= ===============
ops PageLocked(page) i_rwsem invalidate_lock
====================== ======================== ========= ===============
writepage: yes, unlocks (see below)
readpage: yes, unlocks
readpage: yes, unlocks shared
writepages:
set_page_dirty no
readahead: yes, unlocks
readpages: no
readahead: yes, unlocks shared
readpages: no shared
write_begin: locks the page exclusive
write_end: yes, unlocks exclusive
bmap:
invalidatepage: yes
invalidatepage: yes exclusive
releasepage: yes
freepage: yes
direct_IO:
@ -295,7 +295,7 @@ is_partially_uptodate: yes
error_remove_page: yes
swap_activate: no
swap_deactivate: no
====================== ======================== =========
====================== ======================== ========= ===============
->write_begin(), ->write_end() and ->readpage() may be called from
the request handler (/dev/loop).
@ -378,7 +378,10 @@ keep it that way and don't breed new callers.
->invalidatepage() is called when the filesystem must attempt to drop
some or all of the buffers from the page when it is being truncated. It
returns zero on success. If ->invalidatepage is zero, the kernel uses
block_invalidatepage() instead.
block_invalidatepage() instead. The filesystem must exclusively acquire
invalidate_lock before invalidating page cache in truncate / hole punch path
(and thus calling into ->invalidatepage) to block races between page cache
invalidation and page cache filling functions (fault, read, ...).
->releasepage() is called when the kernel is about to try to drop the
buffers from the page in preparation for freeing it. It returns zero to
@ -506,6 +509,7 @@ prototypes::
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
int (*iopoll) (struct kiocb *kiocb, bool spin);
int (*iterate) (struct file *, struct dir_context *);
int (*iterate_shared) (struct file *, struct dir_context *);
__poll_t (*poll) (struct file *, struct poll_table_struct *);
@ -518,12 +522,6 @@ prototypes::
int (*fsync) (struct file *, loff_t start, loff_t end, int datasync);
int (*fasync) (int, struct file *, int);
int (*lock) (struct file *, int, struct file_lock *);
ssize_t (*readv) (struct file *, const struct iovec *, unsigned long,
loff_t *);
ssize_t (*writev) (struct file *, const struct iovec *, unsigned long,
loff_t *);
ssize_t (*sendfile) (struct file *, loff_t *, size_t, read_actor_t,
void __user *);
ssize_t (*sendpage) (struct file *, struct page *, int, size_t,
loff_t *, int);
unsigned long (*get_unmapped_area)(struct file *, unsigned long,
@ -536,6 +534,14 @@ prototypes::
size_t, unsigned int);
int (*setlease)(struct file *, long, struct file_lock **, void **);
long (*fallocate)(struct file *, int, loff_t, loff_t);
void (*show_fdinfo)(struct seq_file *m, struct file *f);
unsigned (*mmap_capabilities)(struct file *);
ssize_t (*copy_file_range)(struct file *, loff_t, struct file *,
loff_t, size_t, unsigned int);
loff_t (*remap_file_range)(struct file *file_in, loff_t pos_in,
struct file *file_out, loff_t pos_out,
loff_t len, unsigned int remap_flags);
int (*fadvise)(struct file *, loff_t, loff_t, int);
locking rules:
All may block.
@ -570,6 +576,25 @@ in sys_read() and friends.
the lease within the individual filesystem to record the result of the
operation
->fallocate implementation must be really careful to maintain page cache
consistency when punching holes or performing other operations that invalidate
page cache contents. Usually the filesystem needs to call
truncate_inode_pages_range() to invalidate relevant range of the page cache.
However the filesystem usually also needs to update its internal (and on disk)
view of file offset -> disk block mapping. Until this update is finished, the
filesystem needs to block page faults and reads from reloading now-stale page
cache contents from the disk. Since VFS acquires mapping->invalidate_lock in
shared mode when loading pages from disk (filemap_fault(), filemap_read(),
readahead paths), the fallocate implementation must take the invalidate_lock to
prevent reloading.
->copy_file_range and ->remap_file_range implementations need to serialize
against modifications of file data while the operation is running. For
blocking changes through write(2) and similar operations inode->i_rwsem can be
used. To block changes to file contents via a memory mapping during the
operation, the filesystem must take mapping->invalidate_lock to coordinate
with ->page_mkwrite.
dquot_operations
================
@ -627,11 +652,11 @@ pfn_mkwrite: yes
access: yes
============= ========= ===========================
->fault() is called when a previously not present pte is about
to be faulted in. The filesystem must find and return the page associated
with the passed in "pgoff" in the vm_fault structure. If it is possible that
the page may be truncated and/or invalidated, then the filesystem must lock
the page, then ensure it is not already truncated (the page lock will block
->fault() is called when a previously not present pte is about to be faulted
in. The filesystem must find and return the page associated with the passed in
"pgoff" in the vm_fault structure. If it is possible that the page may be
truncated and/or invalidated, then the filesystem must lock invalidate_lock,
then ensure the page is not already truncated (invalidate_lock will block
subsequent truncate), and then return with VM_FAULT_LOCKED, and the page
locked. The VM will unlock the page.
@ -644,12 +669,14 @@ page table entry. Pointer to entry associated with the page is passed in
"pte" field in vm_fault structure. Pointers to entries for other offsets
should be calculated relative to "pte".
->page_mkwrite() is called when a previously read-only pte is
about to become writeable. The filesystem again must ensure that there are
no truncate/invalidate races, and then return with the page locked. If
the page has been truncated, the filesystem should not look up a new page
like the ->fault() handler, but simply return with VM_FAULT_NOPAGE, which
will cause the VM to retry the fault.
->page_mkwrite() is called when a previously read-only pte is about to become
writeable. The filesystem again must ensure that there are no
truncate/invalidate races or races with operations such as ->remap_file_range
or ->copy_file_range, and then return with the page locked. Usually
mapping->invalidate_lock is suitable for proper serialization. If the page has
been truncated, the filesystem should not look up a new page like the ->fault()
handler, but simply return with VM_FAULT_NOPAGE, which will cause the VM to
retry the fault.
->pfn_mkwrite() is the same as page_mkwrite but when the pte is
VM_PFNMAP or VM_MIXEDMAP with a page-less entry. Expected return is

9
fs/ceph/addr.c
View File

@ -1395,9 +1395,11 @@ static vm_fault_t ceph_filemap_fault(struct vm_fault *vmf)
ret = VM_FAULT_SIGBUS;
} else {
struct address_space *mapping = inode->i_mapping;
struct page *page = find_or_create_page(mapping, 0,
mapping_gfp_constraint(mapping,
~__GFP_FS));
struct page *page;
filemap_invalidate_lock_shared(mapping);
page = find_or_create_page(mapping, 0,
mapping_gfp_constraint(mapping, ~__GFP_FS));
if (!page) {
ret = VM_FAULT_OOM;
goto out_inline;
@ -1418,6 +1420,7 @@ static vm_fault_t ceph_filemap_fault(struct vm_fault *vmf)
vmf->page = page;
ret = VM_FAULT_MAJOR | VM_FAULT_LOCKED;
out_inline:
filemap_invalidate_unlock_shared(mapping);
dout("filemap_fault %p %llu read inline data ret %x\n",
inode, off, ret);
}

2
fs/ceph/file.c
View File

@ -2088,6 +2088,7 @@ static long ceph_fallocate(struct file *file, int mode,
if (ret < 0)
goto unlock;
filemap_invalidate_lock(inode->i_mapping);
ceph_zero_pagecache_range(inode, offset, length);
ret = ceph_zero_objects(inode, offset, length);
@ -2100,6 +2101,7 @@ static long ceph_fallocate(struct file *file, int mode,
if (dirty)
__mark_inode_dirty(inode, dirty);
}
filemap_invalidate_unlock(inode->i_mapping);
ceph_put_cap_refs(ci, got);
unlock:

2
fs/cifs/smb2ops.c
View File

@ -3590,6 +3590,7 @@ static long smb3_punch_hole(struct file *file, struct cifs_tcon *tcon,
return rc;
}
filemap_invalidate_lock(inode->i_mapping);
/*
* We implement the punch hole through ioctl, so we need remove the page
* caches first, otherwise the data may be inconsistent with the server.
@ -3607,6 +3608,7 @@ static long smb3_punch_hole(struct file *file, struct cifs_tcon *tcon,
sizeof(struct file_zero_data_information),
CIFSMaxBufSize, NULL, NULL);
free_xid(xid);
filemap_invalidate_unlock(inode->i_mapping);
return rc;
}

11
fs/ext2/ext2.h
View File

@ -667,9 +667,6 @@ struct ext2_inode_info {
struct rw_semaphore xattr_sem;
#endif
rwlock_t i_meta_lock;
#ifdef CONFIG_FS_DAX
struct rw_semaphore dax_sem;
#endif
/*
* truncate_mutex is for serialising ext2_truncate() against
@ -685,14 +682,6 @@ struct ext2_inode_info {
#endif
};
#ifdef CONFIG_FS_DAX
#define dax_sem_down_write(ext2_inode) down_write(&(ext2_inode)->dax_sem)
#define dax_sem_up_write(ext2_inode) up_write(&(ext2_inode)->dax_sem)
#else
#define dax_sem_down_write(ext2_inode)
#define dax_sem_up_write(ext2_inode)
#endif
/*
* Inode dynamic state flags
*/

7
fs/ext2/file.c
View File

@ -81,7 +81,7 @@ out_unlock:
*
* mmap_lock (MM)
* sb_start_pagefault (vfs, freeze)
* ext2_inode_info->dax_sem
* address_space->invalidate_lock
* address_space->i_mmap_rwsem or page_lock (mutually exclusive in DAX)
* ext2_inode_info->truncate_mutex
*
@ -91,7 +91,6 @@ out_unlock:
static vm_fault_t ext2_dax_fault(struct vm_fault *vmf)
{
struct inode *inode = file_inode(vmf->vma->vm_file);
struct ext2_inode_info *ei = EXT2_I(inode);
vm_fault_t ret;
bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
(vmf->vma->vm_flags & VM_SHARED);
@ -100,11 +99,11 @@ static vm_fault_t ext2_dax_fault(struct vm_fault *vmf)
sb_start_pagefault(inode->i_sb);
file_update_time(vmf->vma->vm_file);
}
down_read(&ei->dax_sem);
filemap_invalidate_lock_shared(inode->i_mapping);
ret = dax_iomap_fault(vmf, PE_SIZE_PTE, NULL, NULL, &ext2_iomap_ops);
up_read(&ei->dax_sem);
filemap_invalidate_unlock_shared(inode->i_mapping);
if (write)
sb_end_pagefault(inode->i_sb);
return ret;

12
fs/ext2/inode.c
View File

@ -1178,7 +1178,7 @@ static void ext2_free_branches(struct inode *inode, __le32 *p, __le32 *q, int de
ext2_free_data(inode, p, q);
}
/* dax_sem must be held when calling this function */
/* mapping->invalidate_lock must be held when calling this function */
static void __ext2_truncate_blocks(struct inode *inode, loff_t offset)
{
__le32 *i_data = EXT2_I(inode)->i_data;
@ -1195,7 +1195,7 @@ static void __ext2_truncate_blocks(struct inode *inode, loff_t offset)
iblock = (offset + blocksize-1) >> EXT2_BLOCK_SIZE_BITS(inode->i_sb);
#ifdef CONFIG_FS_DAX
WARN_ON(!rwsem_is_locked(&ei->dax_sem));
WARN_ON(!rwsem_is_locked(&inode->i_mapping->invalidate_lock));
#endif
n = ext2_block_to_path(inode, iblock, offsets, NULL);
@ -1277,9 +1277,9 @@ static void ext2_truncate_blocks(struct inode *inode, loff_t offset)
if (ext2_inode_is_fast_symlink(inode))
return;
dax_sem_down_write(EXT2_I(inode));
filemap_invalidate_lock(inode->i_mapping);
__ext2_truncate_blocks(inode, offset);
dax_sem_up_write(EXT2_I(inode));
filemap_invalidate_unlock(inode->i_mapping);
}
static int ext2_setsize(struct inode *inode, loff_t newsize)
@ -1309,10 +1309,10 @@ static int ext2_setsize(struct inode *inode, loff_t newsize)
if (error)
return error;
dax_sem_down_write(EXT2_I(inode));
filemap_invalidate_lock(inode->i_mapping);
truncate_setsize(inode, newsize);
__ext2_truncate_blocks(inode, newsize);
dax_sem_up_write(EXT2_I(inode));
filemap_invalidate_unlock(inode->i_mapping);
inode->i_mtime = inode->i_ctime = current_time(inode);
if (inode_needs_sync(inode)) {

3
fs/ext2/super.c
View File

@ -206,9 +206,6 @@ static void init_once(void *foo)
init_rwsem(&ei->xattr_sem);
#endif
mutex_init(&ei->truncate_mutex);
#ifdef CONFIG_FS_DAX
init_rwsem(&ei->dax_sem);
#endif
inode_init_once(&ei->vfs_inode);
}

10
fs/ext4/ext4.h
View File

@ -1086,15 +1086,6 @@ struct ext4_inode_info {
* by other means, so we have i_data_sem.
*/
struct rw_semaphore i_data_sem;
/*
* i_mmap_sem is for serializing page faults with truncate / punch hole
* operations. We have to make sure that new page cannot be faulted in
* a section of the inode that is being punched. We cannot easily use
* i_data_sem for this since we need protection for the whole punch
* operation and i_data_sem ranks below transaction start so we have
* to occasionally drop it.
*/
struct rw_semaphore i_mmap_sem;
struct inode vfs_inode;
struct jbd2_inode *jinode;
@ -2972,7 +2963,6 @@ extern int ext4_chunk_trans_blocks(struct inode *, int nrblocks);
extern int ext4_zero_partial_blocks(handle_t *handle, struct inode *inode,
loff_t lstart, loff_t lend);
extern vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf);
extern vm_fault_t ext4_filemap_fault(struct vm_fault *vmf);
extern qsize_t *ext4_get_reserved_space(struct inode *inode);
extern int ext4_get_projid(struct inode *inode, kprojid_t *projid);
extern void ext4_da_release_space(struct inode *inode, int to_free);

25
fs/ext4/extents.c
View File

@ -4474,6 +4474,7 @@ static long ext4_zero_range(struct file *file, loff_t offset,
loff_t len, int mode)
{
struct inode *inode = file_inode(file);
struct address_space *mapping = file->f_mapping;
handle_t *handle = NULL;
unsigned int max_blocks;
loff_t new_size = 0;
@ -4560,17 +4561,17 @@ static long ext4_zero_range(struct file *file, loff_t offset,
* Prevent page faults from reinstantiating pages we have
* released from page cache.
*/
down_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_lock(mapping);
ret = ext4_break_layouts(inode);
if (ret) {
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
goto out_mutex;
}
ret = ext4_update_disksize_before_punch(inode, offset, len);
if (ret) {
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
goto out_mutex;
}
/* Now release the pages and zero block aligned part of pages */
@ -4579,7 +4580,7 @@ static long ext4_zero_range(struct file *file, loff_t offset,
ret = ext4_alloc_file_blocks(file, lblk, max_blocks, new_size,
flags);
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
if (ret)
goto out_mutex;
}
@ -5221,6 +5222,7 @@ out:
static int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
{
struct super_block *sb = inode->i_sb;
struct address_space *mapping = inode->i_mapping;
ext4_lblk_t punch_start, punch_stop;
handle_t *handle;
unsigned int credits;
@ -5274,7 +5276,7 @@ static int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
* Prevent page faults from reinstantiating pages we have released from
* page cache.
*/
down_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_lock(mapping);
ret = ext4_break_layouts(inode);
if (ret)
@ -5289,15 +5291,15 @@ static int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
* Write tail of the last page before removed range since it will get
* removed from the page cache below.
*/
ret = filemap_write_and_wait_range(inode->i_mapping, ioffset, offset);
ret = filemap_write_and_wait_range(mapping, ioffset, offset);
if (ret)
goto out_mmap;
/*
* Write data that will be shifted to preserve them when discarding
* page cache below. We are also protected from pages becoming dirty
* by i_mmap_sem.
* by i_rwsem and invalidate_lock.
*/
ret = filemap_write_and_wait_range(inode->i_mapping, offset + len,
ret = filemap_write_and_wait_range(mapping, offset + len,
LLONG_MAX);
if (ret)
goto out_mmap;
@ -5350,7 +5352,7 @@ out_stop:
ext4_journal_stop(handle);
ext4_fc_stop_ineligible(sb);
out_mmap:
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
out_mutex:
inode_unlock(inode);
return ret;
@ -5367,6 +5369,7 @@ out_mutex:
static int ext4_insert_range(struct inode *inode, loff_t offset, loff_t len)
{
struct super_block *sb = inode->i_sb;
struct address_space *mapping = inode->i_mapping;
handle_t *handle;
struct ext4_ext_path *path;
struct ext4_extent *extent;
@ -5425,7 +5428,7 @@ static int ext4_insert_range(struct inode *inode, loff_t offset, loff_t len)
* Prevent page faults from reinstantiating pages we have released from
* page cache.
*/
down_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_lock(mapping);
ret = ext4_break_layouts(inode);
if (ret)
@ -5526,7 +5529,7 @@ out_stop:
ext4_journal_stop(handle);
ext4_fc_stop_ineligible(sb);
out_mmap:
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
out_mutex:
inode_unlock(inode);
return ret;

13
fs/ext4/file.c
View File

@ -704,22 +704,23 @@ static vm_fault_t ext4_dax_huge_fault(struct vm_fault *vmf,
*/
bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
(vmf->vma->vm_flags & VM_SHARED);
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
pfn_t pfn;
if (write) {
sb_start_pagefault(sb);
file_update_time(vmf->vma->vm_file);
down_read(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_lock_shared(mapping);
retry:
handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
EXT4_DATA_TRANS_BLOCKS(sb));
if (IS_ERR(handle)) {
up_read(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock_shared(mapping);
sb_end_pagefault(sb);
return VM_FAULT_SIGBUS;
}
} else {
down_read(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_lock_shared(mapping);
}
result = dax_iomap_fault(vmf, pe_size, &pfn, &error, &ext4_iomap_ops);
if (write) {
@ -731,10 +732,10 @@ retry:
/* Handling synchronous page fault? */
if (result & VM_FAULT_NEEDDSYNC)
result = dax_finish_sync_fault(vmf, pe_size, pfn);
up_read(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock_shared(mapping);
sb_end_pagefault(sb);
} else {
up_read(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock_shared(mapping);
}
return result;
@ -756,7 +757,7 @@ static const struct vm_operations_struct ext4_dax_vm_ops = {
#endif
static const struct vm_operations_struct ext4_file_vm_ops = {
.fault = ext4_filemap_fault,
.fault = filemap_fault,
.map_pages = filemap_map_pages,
.page_mkwrite = ext4_page_mkwrite,
};

47
fs/ext4/inode.c
View File

@ -3950,20 +3950,19 @@ int ext4_update_disksize_before_punch(struct inode *inode, loff_t offset,
return ret;
}
static void ext4_wait_dax_page(struct ext4_inode_info *ei)
static void ext4_wait_dax_page(struct inode *inode)
{
up_write(&ei->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
schedule();
down_write(&ei->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
}
int ext4_break_layouts(struct inode *inode)
{
struct ext4_inode_info *ei = EXT4_I(inode);
struct page *page;
int error;
if (WARN_ON_ONCE(!rwsem_is_locked(&ei->i_mmap_sem)))
if (WARN_ON_ONCE(!rwsem_is_locked(&inode->i_mapping->invalidate_lock)))
return -EINVAL;
do {
@ -3974,7 +3973,7 @@ int ext4_break_layouts(struct inode *inode)
error = ___wait_var_event(&page->_refcount,
atomic_read(&page->_refcount) == 1,
TASK_INTERRUPTIBLE, 0, 0,
ext4_wait_dax_page(ei));
ext4_wait_dax_page(inode));
} while (error == 0);
return error;
@ -4005,9 +4004,9 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
ext4_clear_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA);
if (ext4_has_inline_data(inode)) {
down_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_lock(mapping);
ret = ext4_convert_inline_data(inode);
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
if (ret)
return ret;
}
@ -4058,7 +4057,7 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
* Prevent page faults from reinstantiating pages we have released from
* page cache.
*/
down_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_lock(mapping);
ret = ext4_break_layouts(inode);
if (ret)
@ -4131,7 +4130,7 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
out_stop:
ext4_journal_stop(handle);
out_dio:
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
out_mutex:
inode_unlock(inode);
return ret;
@ -5426,11 +5425,11 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
inode_dio_wait(inode);
}
down_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
rc = ext4_break_layouts(inode);
if (rc) {
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
goto err_out;
}
@ -5506,7 +5505,7 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
error = rc;
}
out_mmap_sem:
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
}
if (!error) {
@ -5983,10 +5982,10 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
* data (and journalled aops don't know how to handle these cases).
*/
if (val) {
down_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
err = filemap_write_and_wait(inode->i_mapping);
if (err < 0) {
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
return err;
}
}
@ -6019,7 +6018,7 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
percpu_up_write(&sbi->s_writepages_rwsem);
if (val)
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
/* Finally we can mark the inode as dirty. */
@ -6063,7 +6062,7 @@ vm_fault_t ext4_page_mkwrite(struct vm_fault *vmf)
sb_start_pagefault(inode->i_sb);
file_update_time(vma->vm_file);
down_read(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_lock_shared(mapping);
err = ext4_convert_inline_data(inode);
if (err)
@ -6176,7 +6175,7 @@ retry_alloc:
out_ret:
ret = block_page_mkwrite_return(err);
out:
up_read(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock_shared(mapping);
sb_end_pagefault(inode->i_sb);
return ret;
out_error:
@ -6184,15 +6183,3 @@ out_error:
ext4_journal_stop(handle);
goto out;
}
vm_fault_t ext4_filemap_fault(struct vm_fault *vmf)
{
struct inode *inode = file_inode(vmf->vma->vm_file);
vm_fault_t ret;
down_read(&EXT4_I(inode)->i_mmap_sem);
ret = filemap_fault(vmf);
up_read(&EXT4_I(inode)->i_mmap_sem);
return ret;
}

4
fs/ext4/ioctl.c
View File

@ -148,7 +148,7 @@ static long swap_inode_boot_loader(struct super_block *sb,
goto journal_err_out;
}
down_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
err = filemap_write_and_wait(inode->i_mapping);
if (err)
goto err_out;
@ -256,7 +256,7 @@ err_out1:
ext4_double_up_write_data_sem(inode, inode_bl);
err_out:
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
journal_err_out:
unlock_two_nondirectories(inode, inode_bl);
iput(inode_bl);

13
fs/ext4/super.c
View File

@ -90,12 +90,9 @@ static struct inode *ext4_get_journal_inode(struct super_block *sb,
/*
* Lock ordering
*
* Note the difference between i_mmap_sem (EXT4_I(inode)->i_mmap_sem) and
* i_mmap_rwsem (inode->i_mmap_rwsem)!
*
* page fault path:
* mmap_lock -> sb_start_pagefault -> i_mmap_sem (r) -> transaction start ->
* page lock -> i_data_sem (rw)
* mmap_lock -> sb_start_pagefault -> invalidate_lock (r) -> transaction start
* -> page lock -> i_data_sem (rw)
*
* buffered write path:
* sb_start_write -> i_mutex -> mmap_lock
@ -103,8 +100,9 @@ static struct inode *ext4_get_journal_inode(struct super_block *sb,
* i_data_sem (rw)
*
* truncate:
* sb_start_write -> i_mutex -> i_mmap_sem (w) -> i_mmap_rwsem (w) -> page lock
* sb_start_write -> i_mutex -> i_mmap_sem (w) -> transaction start ->
* sb_start_write -> i_mutex -> invalidate_lock (w) -> i_mmap_rwsem (w) ->
* page lock
* sb_start_write -> i_mutex -> invalidate_lock (w) -> transaction start ->
* i_data_sem (rw)
*
* direct IO:
@ -1360,7 +1358,6 @@ static void init_once(void *foo)
INIT_LIST_HEAD(&ei->i_orphan);
init_rwsem(&ei->xattr_sem);
init_rwsem(&ei->i_data_sem);
init_rwsem(&ei->i_mmap_sem);
inode_init_once(&ei->vfs_inode);
ext4_fc_init_inode(&ei->vfs_inode);
}

8
fs/ext4/truncate.h
View File

@ -11,14 +11,16 @@
*/
static inline void ext4_truncate_failed_write(struct inode *inode)
{
struct address_space *mapping = inode->i_mapping;
/*
* We don't need to call ext4_break_layouts() because the blocks we
* are truncating were never visible to userspace.
*/
down_write(&EXT4_I(inode)->i_mmap_sem);
truncate_inode_pages(inode->i_mapping, inode->i_size);
filemap_invalidate_lock(mapping);
truncate_inode_pages(mapping, inode->i_size);
ext4_truncate(inode);
up_write(&EXT4_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
}
/*

8
fs/f2fs/data.c
View File

@ -3187,12 +3187,12 @@ static void f2fs_write_failed(struct address_space *mapping, loff_t to)
/* In the fs-verity case, f2fs_end_enable_verity() does the truncate */
if (to > i_size && !f2fs_verity_in_progress(inode)) {
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(mapping);
truncate_pagecache(inode, i_size);
f2fs_truncate_blocks(inode, i_size, true);
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
}
}
@ -3852,7 +3852,7 @@ static int f2fs_migrate_blocks(struct inode *inode, block_t start_blk,
int ret = 0;
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
set_inode_flag(inode, FI_ALIGNED_WRITE);
@ -3894,7 +3894,7 @@ done:
clear_inode_flag(inode, FI_DO_DEFRAG);
clear_inode_flag(inode, FI_ALIGNED_WRITE);
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
return ret;

1
fs/f2fs/f2fs.h
View File

@ -754,7 +754,6 @@ struct f2fs_inode_info {
/* avoid racing between foreground op and gc */
struct rw_semaphore i_gc_rwsem[2];
struct rw_semaphore i_mmap_sem;
struct rw_semaphore i_xattr_sem; /* avoid racing between reading and changing EAs */
int i_extra_isize; /* size of extra space located in i_addr */

62
fs/f2fs/file.c
View File

@ -38,10 +38,7 @@ static vm_fault_t f2fs_filemap_fault(struct vm_fault *vmf)
struct inode *inode = file_inode(vmf->vma->vm_file);
vm_fault_t ret;
down_read(&F2FS_I(inode)->i_mmap_sem);
ret = filemap_fault(vmf);
up_read(&F2FS_I(inode)->i_mmap_sem);
if (!ret)
f2fs_update_iostat(F2FS_I_SB(inode), APP_MAPPED_READ_IO,
F2FS_BLKSIZE);
@ -101,7 +98,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
f2fs_bug_on(sbi, f2fs_has_inline_data(inode));
file_update_time(vmf->vma->vm_file);
down_read(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock_shared(inode->i_mapping);
lock_page(page);
if (unlikely(page->mapping != inode->i_mapping ||
page_offset(page) > i_size_read(inode) ||
@ -159,7 +156,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
trace_f2fs_vm_page_mkwrite(page, DATA);
out_sem:
up_read(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock_shared(inode->i_mapping);
sb_end_pagefault(inode->i_sb);
err:
@ -940,7 +937,7 @@ int f2fs_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
}
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
truncate_setsize(inode, attr->ia_size);
@ -950,7 +947,7 @@ int f2fs_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
* do not trim all blocks after i_size if target size is
* larger than i_size.
*/
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
if (err)
return err;
@ -1095,7 +1092,7 @@ static int punch_hole(struct inode *inode, loff_t offset, loff_t len)
blk_end = (loff_t)pg_end << PAGE_SHIFT;
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(mapping);
truncate_inode_pages_range(mapping, blk_start,
blk_end - 1);
@ -1104,7 +1101,7 @@ static int punch_hole(struct inode *inode, loff_t offset, loff_t len)
ret = f2fs_truncate_hole(inode, pg_start, pg_end);
f2fs_unlock_op(sbi);
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
}
}
@ -1339,7 +1336,7 @@ static int f2fs_do_collapse(struct inode *inode, loff_t offset, loff_t len)
/* avoid gc operation during block exchange */
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
f2fs_lock_op(sbi);
f2fs_drop_extent_tree(inode);
@ -1347,7 +1344,7 @@ static int f2fs_do_collapse(struct inode *inode, loff_t offset, loff_t len)
ret = __exchange_data_block(inode, inode, end, start, nrpages - end, true);
f2fs_unlock_op(sbi);
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
return ret;
}
@ -1378,13 +1375,13 @@ static int f2fs_collapse_range(struct inode *inode, loff_t offset, loff_t len)
return ret;
/* write out all moved pages, if possible */
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX);
truncate_pagecache(inode, offset);
new_size = i_size_read(inode) - len;
ret = f2fs_truncate_blocks(inode, new_size, true);
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
if (!ret)
f2fs_i_size_write(inode, new_size);
return ret;
@ -1484,7 +1481,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len,
pgoff_t end;
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(mapping);
truncate_pagecache_range(inode,
(loff_t)index << PAGE_SHIFT,
@ -1496,7 +1493,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len,
ret = f2fs_get_dnode_of_data(&dn, index, ALLOC_NODE);
if (ret) {
f2fs_unlock_op(sbi);
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
goto out;
}
@ -1508,7 +1505,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len,
f2fs_put_dnode(&dn);
f2fs_unlock_op(sbi);
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
f2fs_balance_fs(sbi, dn.node_changed);
@ -1543,6 +1540,7 @@ out:
static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
{
struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
struct address_space *mapping = inode->i_mapping;
pgoff_t nr, pg_start, pg_end, delta, idx;
loff_t new_size;
int ret = 0;
@ -1565,14 +1563,14 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
f2fs_balance_fs(sbi, true);
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(mapping);
ret = f2fs_truncate_blocks(inode, i_size_read(inode), true);
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
if (ret)
return ret;
/* write out all dirty pages from offset */
ret = filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX);
ret = filemap_write_and_wait_range(mapping, offset, LLONG_MAX);
if (ret)
return ret;
@ -1583,7 +1581,7 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
/* avoid gc operation during block exchange */
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(mapping);
truncate_pagecache(inode, offset);
while (!ret && idx > pg_start) {
@ -1599,14 +1597,14 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
idx + delta, nr, false);
f2fs_unlock_op(sbi);
}
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
/* write out all moved pages, if possible */
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX);
filemap_invalidate_lock(mapping);
filemap_write_and_wait_range(mapping, offset, LLONG_MAX);
truncate_pagecache(inode, offset);
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
if (!ret)
f2fs_i_size_write(inode, new_size);
@ -3440,7 +3438,7 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
goto out;
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
last_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
@ -3476,7 +3474,7 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
}
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
out:
inode_unlock(inode);
@ -3593,7 +3591,7 @@ static int f2fs_reserve_compress_blocks(struct file *filp, unsigned long arg)
}
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
last_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
@ -3629,7 +3627,7 @@ static int f2fs_reserve_compress_blocks(struct file *filp, unsigned long arg)
}
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
if (ret >= 0) {
clear_inode_flag(inode, FI_COMPRESS_RELEASED);
@ -3748,7 +3746,7 @@ static int f2fs_sec_trim_file(struct file *filp, unsigned long arg)
goto err;
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(mapping);
ret = filemap_write_and_wait_range(mapping, range.start,
to_end ? LLONG_MAX : end_addr - 1);
@ -3835,7 +3833,7 @@ static int f2fs_sec_trim_file(struct file *filp, unsigned long arg)
ret = f2fs_secure_erase(prev_bdev, inode, prev_index,
prev_block, len, range.flags);
out:
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(mapping);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
err:
inode_unlock(inode);
@ -4313,9 +4311,9 @@ write:
/* if we couldn't write data, we should deallocate blocks. */
if (preallocated && i_size_read(inode) < target_size) {
down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
down_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
f2fs_truncate(inode);
up_write(&F2FS_I(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
}

1
fs/f2fs/super.c
View File

@ -1289,7 +1289,6 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb)
mutex_init(&fi->inmem_lock);
init_rwsem(&fi->i_gc_rwsem[READ]);
init_rwsem(&fi->i_gc_rwsem[WRITE]);
init_rwsem(&fi->i_mmap_sem);
init_rwsem(&fi->i_xattr_sem);
/* Will be used by directory only */

50
fs/fuse/dax.c
View File

@ -444,12 +444,12 @@ static int fuse_setup_new_dax_mapping(struct inode *inode, loff_t pos,
/*
* Can't do inline reclaim in fault path. We call
* dax_layout_busy_page() before we free a range. And
* fuse_wait_dax_page() drops fi->i_mmap_sem lock and requires it.
* In fault path we enter with fi->i_mmap_sem held and can't drop
* it. Also in fault path we hold fi->i_mmap_sem shared and not
* exclusive, so that creates further issues with fuse_wait_dax_page().
* Hence return -EAGAIN and fuse_dax_fault() will wait for a memory
* range to become free and retry.
* fuse_wait_dax_page() drops mapping->invalidate_lock and requires it.
* In fault path we enter with mapping->invalidate_lock held and can't
* drop it. Also in fault path we hold mapping->invalidate_lock shared
* and not exclusive, so that creates further issues with
* fuse_wait_dax_page(). Hence return -EAGAIN and fuse_dax_fault()
* will wait for a memory range to become free and retry.
*/
if (flags & IOMAP_FAULT) {
alloc_dmap = alloc_dax_mapping(fcd);
@ -513,7 +513,7 @@ static int fuse_upgrade_dax_mapping(struct inode *inode, loff_t pos,
down_write(&fi->dax->sem);
node = interval_tree_iter_first(&fi->dax->tree, idx, idx);
/* We are holding either inode lock or i_mmap_sem, and that should
/* We are holding either inode lock or invalidate_lock, and that should
* ensure that dmap can't be truncated. We are holding a reference
* on dmap and that should make sure it can't be reclaimed. So dmap
* should still be there in tree despite the fact we dropped and
@ -660,14 +660,12 @@ static const struct iomap_ops fuse_iomap_ops = {
static void fuse_wait_dax_page(struct inode *inode)
{
struct fuse_inode *fi = get_fuse_inode(inode);
up_write(&fi->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
schedule();
down_write(&fi->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
}
/* Should be called with fi->i_mmap_sem lock held exclusively */
/* Should be called with mapping->invalidate_lock held exclusively */
static int __fuse_dax_break_layouts(struct inode *inode, bool *retry,
loff_t start, loff_t end)
{
@ -813,18 +811,18 @@ retry:
* we do not want any read/write/mmap to make progress and try
* to populate page cache or access memory we are trying to free.
*/
down_read(&get_fuse_inode(inode)->i_mmap_sem);
filemap_invalidate_lock_shared(inode->i_mapping);
ret = dax_iomap_fault(vmf, pe_size, &pfn, &error, &fuse_iomap_ops);
if ((ret & VM_FAULT_ERROR) && error == -EAGAIN) {
error = 0;
retry = true;
up_read(&get_fuse_inode(inode)->i_mmap_sem);
filemap_invalidate_unlock_shared(inode->i_mapping);
goto retry;
}
if (ret & VM_FAULT_NEEDDSYNC)
ret = dax_finish_sync_fault(vmf, pe_size, pfn);
up_read(&get_fuse_inode(inode)->i_mmap_sem);
filemap_invalidate_unlock_shared(inode->i_mapping);
if (write)
sb_end_pagefault(sb);
@ -960,7 +958,7 @@ inode_inline_reclaim_one_dmap(struct fuse_conn_dax *fcd, struct inode *inode,
int ret;
struct interval_tree_node *node;
down_write(&fi->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
/* Lookup a dmap and corresponding file offset to reclaim. */
down_read(&fi->dax->sem);
@ -1021,7 +1019,7 @@ inode_inline_reclaim_one_dmap(struct fuse_conn_dax *fcd, struct inode *inode,
out_write_dmap_sem:
up_write(&fi->dax->sem);
out_mmap_sem:
up_write(&fi->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
return dmap;
}
@ -1050,10 +1048,10 @@ alloc_dax_mapping_reclaim(struct fuse_conn_dax *fcd, struct inode *inode)
* had a reference or some other temporary failure,
* Try again. We want to give up inline reclaim only
* if there is no range assigned to this node. Otherwise
* if a deadlock is possible if we sleep with fi->i_mmap_sem
* held and worker to free memory can't make progress due
* to unavailability of fi->i_mmap_sem lock. So sleep
* only if fi->dax->nr=0
* if a deadlock is possible if we sleep with
* mapping->invalidate_lock held and worker to free memory
* can't make progress due to unavailability of
* mapping->invalidate_lock. So sleep only if fi->dax->nr=0
*/
if (retry)
continue;
@ -1061,8 +1059,8 @@ alloc_dax_mapping_reclaim(struct fuse_conn_dax *fcd, struct inode *inode)
* There are no mappings which can be reclaimed. Wait for one.
* We are not holding fi->dax->sem. So it is possible
* that range gets added now. But as we are not holding
* fi->i_mmap_sem, worker should still be able to free up
* a range and wake us up.
* mapping->invalidate_lock, worker should still be able to
* free up a range and wake us up.
*/
if (!fi->dax->nr && !(fcd->nr_free_ranges > 0)) {
if (wait_event_killable_exclusive(fcd->range_waitq,
@ -1108,7 +1106,7 @@ static int lookup_and_reclaim_dmap_locked(struct fuse_conn_dax *fcd,
/*
* Free a range of memory.
* Locking:
* 1. Take fi->i_mmap_sem to block dax faults.
* 1. Take mapping->invalidate_lock to block dax faults.
* 2. Take fi->dax->sem to protect interval tree and also to make sure
* read/write can not reuse a dmap which we might be freeing.
*/
@ -1122,7 +1120,7 @@ static int lookup_and_reclaim_dmap(struct fuse_conn_dax *fcd,
loff_t dmap_start = start_idx << FUSE_DAX_SHIFT;
loff_t dmap_end = (dmap_start + FUSE_DAX_SZ) - 1;
down_write(&fi->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
ret = fuse_dax_break_layouts(inode, dmap_start, dmap_end);
if (ret) {
pr_debug("virtio_fs: fuse_dax_break_layouts() failed. err=%d\n",
@ -1134,7 +1132,7 @@ static int lookup_and_reclaim_dmap(struct fuse_conn_dax *fcd,
ret = lookup_and_reclaim_dmap_locked(fcd, inode, start_idx);
up_write(&fi->dax->sem);
out_mmap_sem:
up_write(&fi->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
return ret;
}

11
fs/fuse/dir.c
View File

@ -1556,6 +1556,7 @@ int fuse_do_setattr(struct dentry *dentry, struct iattr *attr,
struct fuse_mount *fm = get_fuse_mount(inode);
struct fuse_conn *fc = fm->fc;
struct fuse_inode *fi = get_fuse_inode(inode);
struct address_space *mapping = inode->i_mapping;
FUSE_ARGS(args);
struct fuse_setattr_in inarg;
struct fuse_attr_out outarg;
@ -1580,11 +1581,11 @@ int fuse_do_setattr(struct dentry *dentry, struct iattr *attr,
}
if (FUSE_IS_DAX(inode) && is_truncate) {
down_write(&fi->i_mmap_sem);
filemap_invalidate_lock(mapping);
fault_blocked = true;
err = fuse_dax_break_layouts(inode, 0, 0);
if (err) {
up_write(&fi->i_mmap_sem);
filemap_invalidate_unlock(mapping);
return err;
}
}
@ -1694,13 +1695,13 @@ int fuse_do_setattr(struct dentry *dentry, struct iattr *attr,
if ((is_truncate || !is_wb) &&
S_ISREG(inode->i_mode) && oldsize != outarg.attr.size) {
truncate_pagecache(inode, outarg.attr.size);
invalidate_inode_pages2(inode->i_mapping);
invalidate_inode_pages2(mapping);
}
clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
out:
if (fault_blocked)
up_write(&fi->i_mmap_sem);
filemap_invalidate_unlock(mapping);
return 0;
@ -1711,7 +1712,7 @@ error:
clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
if (fault_blocked)
up_write(&fi->i_mmap_sem);
filemap_invalidate_unlock(mapping);
return err;
}

10
fs/fuse/file.c
View File

@ -243,7 +243,7 @@ int fuse_open_common(struct inode *inode, struct file *file, bool isdir)
}
if (dax_truncate) {
down_write(&get_fuse_inode(inode)->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
err = fuse_dax_break_layouts(inode, 0, 0);
if (err)
goto out;
@ -255,7 +255,7 @@ int fuse_open_common(struct inode *inode, struct file *file, bool isdir)
out:
if (dax_truncate)
up_write(&get_fuse_inode(inode)->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
if (is_wb_truncate | dax_truncate) {
fuse_release_nowrite(inode);
@ -2920,7 +2920,7 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
if (lock_inode) {
inode_lock(inode);
if (block_faults) {
down_write(&fi->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
err = fuse_dax_break_layouts(inode, 0, 0);
if (err)
goto out;
@ -2976,7 +2976,7 @@ out:
clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
if (block_faults)
up_write(&fi->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
if (lock_inode)
inode_unlock(inode);
@ -3045,7 +3045,7 @@ static ssize_t __fuse_copy_file_range(struct file *file_in, loff_t pos_in,
* modifications. Yet this does give less guarantees than if the
* copying was performed with write(2).
*
* To fix this a i_mmap_sem style lock could be used to prevent new
* To fix this a mapping->invalidate_lock could be used to prevent new
* faults while the copy is ongoing.
*/
err = fuse_writeback_range(inode_out, pos_out, pos_out + len - 1);

7
fs/fuse/fuse_i.h
View File

@ -149,13 +149,6 @@ struct fuse_inode {
/** Lock to protect write related fields */
spinlock_t lock;
/**
* Can't take inode lock in fault path (leads to circular dependency).
* Introduce another semaphore which can be taken in fault path and
* then other filesystem paths can take this to block faults.
*/
struct rw_semaphore i_mmap_sem;
#ifdef CONFIG_FUSE_DAX
/*
* Dax specific inode data

1
fs/fuse/inode.c
View File

@ -85,7 +85,6 @@ static struct inode *fuse_alloc_inode(struct super_block *sb)
fi->orig_ino = 0;
fi->state = 0;
mutex_init(&fi->mutex);
init_rwsem(&fi->i_mmap_sem);
spin_lock_init(&fi->lock);
fi->forget = fuse_alloc_forget();
if (!fi->forget)

2
fs/inode.c
View File

@ -190,6 +190,8 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE);
mapping->private_data = NULL;
mapping->writeback_index = 0;
__init_rwsem(&mapping->invalidate_lock, "mapping.invalidate_lock",
&sb->s_type->invalidate_lock_key);
inode->i_private = NULL;
inode->i_mapping = mapping;
INIT_HLIST_HEAD(&inode->i_dentry); /* buggered by rcu freeing */

15
fs/xfs/xfs_bmap_util.c
View File

@ -1626,7 +1626,6 @@ xfs_swap_extents(
struct xfs_bstat *sbp = &sxp->sx_stat;
int src_log_flags, target_log_flags;
int error = 0;
int lock_flags;
uint64_t f;
int resblks = 0;
unsigned int flags = 0;
@ -1638,8 +1637,8 @@ xfs_swap_extents(
* do the rest of the checks.
*/
lock_two_nondirectories(VFS_I(ip), VFS_I(tip));
lock_flags = XFS_MMAPLOCK_EXCL;
xfs_lock_two_inodes(ip, XFS_MMAPLOCK_EXCL, tip, XFS_MMAPLOCK_EXCL);
filemap_invalidate_lock_two(VFS_I(ip)->i_mapping,
VFS_I(tip)->i_mapping);
/* Verify that both files have the same format */
if ((VFS_I(ip)->i_mode & S_IFMT) != (VFS_I(tip)->i_mode & S_IFMT)) {
@ -1711,7 +1710,6 @@ xfs_swap_extents(
* or cancel will unlock the inodes from this point onwards.
*/
xfs_lock_two_inodes(ip, XFS_ILOCK_EXCL, tip, XFS_ILOCK_EXCL);
lock_flags |= XFS_ILOCK_EXCL;
xfs_trans_ijoin(tp, ip, 0);
xfs_trans_ijoin(tp, tip, 0);
@ -1830,13 +1828,16 @@ xfs_swap_extents(
trace_xfs_swap_extent_after(ip, 0);
trace_xfs_swap_extent_after(tip, 1);
out_unlock_ilock:
xfs_iunlock(ip, XFS_ILOCK_EXCL);
xfs_iunlock(tip, XFS_ILOCK_EXCL);
out_unlock:
xfs_iunlock(ip, lock_flags);
xfs_iunlock(tip, lock_flags);
filemap_invalidate_unlock_two(VFS_I(ip)->i_mapping,
VFS_I(tip)->i_mapping);
unlock_two_nondirectories(VFS_I(ip), VFS_I(tip));
return error;
out_trans_cancel:
xfs_trans_cancel(tp);
goto out_unlock;
goto out_unlock_ilock;
}

13
fs/xfs/xfs_file.c
View File

@ -1302,7 +1302,7 @@ xfs_file_llseek(
*
* mmap_lock (MM)
* sb_start_pagefault(vfs, freeze)
* i_mmaplock (XFS - truncate serialisation)
* invalidate_lock (vfs/XFS_MMAPLOCK - truncate serialisation)
* page_lock (MM)
* i_lock (XFS - extent map serialisation)
*/
@ -1323,24 +1323,27 @@ __xfs_filemap_fault(
file_update_time(vmf->vma->vm_file);
}
xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
if (IS_DAX(inode)) {
pfn_t pfn;
xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL,
(write_fault && !vmf->cow_page) ?
&xfs_direct_write_iomap_ops :
&xfs_read_iomap_ops);
if (ret & VM_FAULT_NEEDDSYNC)
ret = dax_finish_sync_fault(vmf, pe_size, pfn);
xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
} else {
if (write_fault)
if (write_fault) {
xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
ret = iomap_page_mkwrite(vmf,
&xfs_buffered_write_iomap_ops);
else
xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
} else {
ret = filemap_fault(vmf);
}
}
xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
if (write_fault)
sb_end_pagefault(inode->i_sb);

121
fs/xfs/xfs_inode.c
View File

@ -132,7 +132,7 @@ xfs_ilock_attr_map_shared(
/*
* In addition to i_rwsem in the VFS inode, the xfs inode contains 2
* multi-reader locks: i_mmap_lock and the i_lock. This routine allows
* multi-reader locks: invalidate_lock and the i_lock. This routine allows
* various combinations of the locks to be obtained.
*
* The 3 locks should always be ordered so that the IO lock is obtained first,
@ -140,23 +140,23 @@ xfs_ilock_attr_map_shared(
*
* Basic locking order:
*
* i_rwsem -> i_mmap_lock -> page_lock -> i_ilock
* i_rwsem -> invalidate_lock -> page_lock -> i_ilock
*
* mmap_lock locking order:
*
* i_rwsem -> page lock -> mmap_lock
* mmap_lock -> i_mmap_lock -> page_lock
* mmap_lock -> invalidate_lock -> page_lock
*
* The difference in mmap_lock locking order mean that we cannot hold the
* i_mmap_lock over syscall based read(2)/write(2) based IO. These IO paths can
* fault in pages during copy in/out (for buffered IO) or require the mmap_lock
* in get_user_pages() to map the user pages into the kernel address space for
* direct IO. Similarly the i_rwsem cannot be taken inside a page fault because
* page faults already hold the mmap_lock.
* invalidate_lock over syscall based read(2)/write(2) based IO. These IO paths
* can fault in pages during copy in/out (for buffered IO) or require the
* mmap_lock in get_user_pages() to map the user pages into the kernel address
* space for direct IO. Similarly the i_rwsem cannot be taken inside a page
* fault because page faults already hold the mmap_lock.
*
* Hence to serialise fully against both syscall and mmap based IO, we need to
* take both the i_rwsem and the i_mmap_lock. These locks should *only* be both
* taken in places where we need to invalidate the page cache in a race
* take both the i_rwsem and the invalidate_lock. These locks should *only* be
* both taken in places where we need to invalidate the page cache in a race
* free manner (e.g. truncate, hole punch and other extent manipulation
* functions).
*/
@ -188,10 +188,13 @@ xfs_ilock(
XFS_IOLOCK_DEP(lock_flags));
}
if (lock_flags & XFS_MMAPLOCK_EXCL)
mrupdate_nested(&ip->i_mmaplock, XFS_MMAPLOCK_DEP(lock_flags));
else if (lock_flags & XFS_MMAPLOCK_SHARED)
mraccess_nested(&ip->i_mmaplock, XFS_MMAPLOCK_DEP(lock_flags));
if (lock_flags & XFS_MMAPLOCK_EXCL) {
down_write_nested(&VFS_I(ip)->i_mapping->invalidate_lock,
XFS_MMAPLOCK_DEP(lock_flags));
} else if (lock_flags & XFS_MMAPLOCK_SHARED) {
down_read_nested(&VFS_I(ip)->i_mapping->invalidate_lock,
XFS_MMAPLOCK_DEP(lock_flags));
}
if (lock_flags & XFS_ILOCK_EXCL)
mrupdate_nested(&ip->i_lock, XFS_ILOCK_DEP(lock_flags));
@ -240,10 +243,10 @@ xfs_ilock_nowait(
}
if (lock_flags & XFS_MMAPLOCK_EXCL) {
if (!mrtryupdate(&ip->i_mmaplock))
if (!down_write_trylock(&VFS_I(ip)->i_mapping->invalidate_lock))
goto out_undo_iolock;
} else if (lock_flags & XFS_MMAPLOCK_SHARED) {
if (!mrtryaccess(&ip->i_mmaplock))
if (!down_read_trylock(&VFS_I(ip)->i_mapping->invalidate_lock))
goto out_undo_iolock;
}
@ -258,9 +261,9 @@ xfs_ilock_nowait(
out_undo_mmaplock:
if (lock_flags & XFS_MMAPLOCK_EXCL)
mrunlock_excl(&ip->i_mmaplock);
up_write(&VFS_I(ip)->i_mapping->invalidate_lock);
else if (lock_flags & XFS_MMAPLOCK_SHARED)
mrunlock_shared(&ip->i_mmaplock);
up_read(&VFS_I(ip)->i_mapping->invalidate_lock);
out_undo_iolock:
if (lock_flags & XFS_IOLOCK_EXCL)
up_write(&VFS_I(ip)->i_rwsem);
@ -307,9 +310,9 @@ xfs_iunlock(
up_read(&VFS_I(ip)->i_rwsem);
if (lock_flags & XFS_MMAPLOCK_EXCL)
mrunlock_excl(&ip->i_mmaplock);
up_write(&VFS_I(ip)->i_mapping->invalidate_lock);
else if (lock_flags & XFS_MMAPLOCK_SHARED)
mrunlock_shared(&ip->i_mmaplock);
up_read(&VFS_I(ip)->i_mapping->invalidate_lock);
if (lock_flags & XFS_ILOCK_EXCL)
mrunlock_excl(&ip->i_lock);
@ -335,7 +338,7 @@ xfs_ilock_demote(
if (lock_flags & XFS_ILOCK_EXCL)
mrdemote(&ip->i_lock);
if (lock_flags & XFS_MMAPLOCK_EXCL)
mrdemote(&ip->i_mmaplock);
downgrade_write(&VFS_I(ip)->i_mapping->invalidate_lock);
if (lock_flags & XFS_IOLOCK_EXCL)
downgrade_write(&VFS_I(ip)->i_rwsem);
@ -343,9 +346,29 @@ xfs_ilock_demote(
}
#if defined(DEBUG) || defined(XFS_WARN)
int
static inline bool
__xfs_rwsem_islocked(
struct rw_semaphore *rwsem,
bool shared)
{
if (!debug_locks)
return rwsem_is_locked(rwsem);
if (!shared)
return lockdep_is_held_type(rwsem, 0);
/*
* We are checking that the lock is held at least in shared
* mode but don't care that it might be held exclusively
* (i.e. shared | excl). Hence we check if the lock is held
* in any mode rather than an explicit shared mode.
*/
return lockdep_is_held_type(rwsem, -1);
}
bool
xfs_isilocked(
xfs_inode_t *ip,
struct xfs_inode *ip,
uint lock_flags)
{
if (lock_flags & (XFS_ILOCK_EXCL|XFS_ILOCK_SHARED)) {
@ -355,20 +378,17 @@ xfs_isilocked(
}
if (lock_flags & (XFS_MMAPLOCK_EXCL|XFS_MMAPLOCK_SHARED)) {
if (!(lock_flags & XFS_MMAPLOCK_SHARED))
return !!ip->i_mmaplock.mr_writer;
return rwsem_is_locked(&ip->i_mmaplock.mr_lock);
return __xfs_rwsem_islocked(&VFS_I(ip)->i_rwsem,
(lock_flags & XFS_IOLOCK_SHARED));
}
if (lock_flags & (XFS_IOLOCK_EXCL|XFS_IOLOCK_SHARED)) {
if (!(lock_flags & XFS_IOLOCK_SHARED))
return !debug_locks ||
lockdep_is_held_type(&VFS_I(ip)->i_rwsem, 0);
return rwsem_is_locked(&VFS_I(ip)->i_rwsem);
if (lock_flags & (XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED)) {
return __xfs_rwsem_islocked(&VFS_I(ip)->i_rwsem,
(lock_flags & XFS_IOLOCK_SHARED));
}
ASSERT(0);
return 0;
return false;
}
#endif
@ -532,12 +552,10 @@ again:
}
/*
* xfs_lock_two_inodes() can only be used to lock one type of lock at a time -
* the mmaplock or the ilock, but not more than one type at a time. If we lock
* more than one at a time, lockdep will report false positives saying we have
* violated locking orders. The iolock must be double-locked separately since
* we use i_rwsem for that. We now support taking one lock EXCL and the other
* SHARED.
* xfs_lock_two_inodes() can only be used to lock ilock. The iolock and
* mmaplock must be double-locked separately since we use i_rwsem and
* invalidate_lock for that. We now support taking one lock EXCL and the
* other SHARED.
*/
void
xfs_lock_two_inodes(
@ -555,15 +573,8 @@ xfs_lock_two_inodes(
ASSERT(hweight32(ip1_mode) == 1);
ASSERT(!(ip0_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL)));
ASSERT(!(ip1_mode & (XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL)));
ASSERT(!(ip0_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)) ||
!(ip0_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)));
ASSERT(!(ip1_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)) ||
!(ip1_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)));
ASSERT(!(ip1_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)) ||
!(ip0_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)));
ASSERT(!(ip0_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)) ||
!(ip1_mode & (XFS_ILOCK_SHARED|XFS_ILOCK_EXCL)));
ASSERT(!(ip0_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)));
ASSERT(!(ip1_mode & (XFS_MMAPLOCK_SHARED|XFS_MMAPLOCK_EXCL)));
ASSERT(ip0->i_ino != ip1->i_ino);
if (ip0->i_ino > ip1->i_ino) {
@ -3741,11 +3752,8 @@ xfs_ilock2_io_mmap(
ret = xfs_iolock_two_inodes_and_break_layout(VFS_I(ip1), VFS_I(ip2));
if (ret)
return ret;
if (ip1 == ip2)
xfs_ilock(ip1, XFS_MMAPLOCK_EXCL);
else
xfs_lock_two_inodes(ip1, XFS_MMAPLOCK_EXCL,
ip2, XFS_MMAPLOCK_EXCL);
filemap_invalidate_lock_two(VFS_I(ip1)->i_mapping,
VFS_I(ip2)->i_mapping);
return 0;
}
@ -3755,12 +3763,9 @@ xfs_iunlock2_io_mmap(
struct xfs_inode *ip1,
struct xfs_inode *ip2)
{
bool same_inode = (ip1 == ip2);
xfs_iunlock(ip2, XFS_MMAPLOCK_EXCL);
if (!same_inode)
xfs_iunlock(ip1, XFS_MMAPLOCK_EXCL);
filemap_invalidate_unlock_two(VFS_I(ip1)->i_mapping,
VFS_I(ip2)->i_mapping);
inode_unlock(VFS_I(ip2));
if (!same_inode)
if (ip1 != ip2)
inode_unlock(VFS_I(ip1));
}

3
fs/xfs/xfs_inode.h
View File

@ -40,7 +40,6 @@ typedef struct xfs_inode {
/* Transaction and locking information. */
struct xfs_inode_log_item *i_itemp; /* logging information */
mrlock_t i_lock; /* inode lock */
mrlock_t i_mmaplock; /* inode mmap IO lock */
atomic_t i_pincount; /* inode pin count */
/*
@ -410,7 +409,7 @@ void xfs_ilock(xfs_inode_t *, uint);
int xfs_ilock_nowait(xfs_inode_t *, uint);
void xfs_iunlock(xfs_inode_t *, uint);
void xfs_ilock_demote(xfs_inode_t *, uint);
int xfs_isilocked(xfs_inode_t *, uint);
bool xfs_isilocked(struct xfs_inode *, uint);
uint xfs_ilock_data_map_shared(struct xfs_inode *);
uint xfs_ilock_attr_map_shared(struct xfs_inode *);

2
fs/xfs/xfs_super.c
View File

@ -709,8 +709,6 @@ xfs_fs_inode_init_once(
atomic_set(&ip->i_pincount, 0);
spin_lock_init(&ip->i_flags_lock);
mrlock_init(&ip->i_mmaplock, MRLOCK_ALLOW_EQUAL_PRI|MRLOCK_BARRIER,
"xfsino", ip->i_ino);
mrlock_init(&ip->i_lock, MRLOCK_ALLOW_EQUAL_PRI|MRLOCK_BARRIER,
"xfsino", ip->i_ino);
}

23
fs/zonefs/super.c
View File

@ -462,7 +462,7 @@ static int zonefs_file_truncate(struct inode *inode, loff_t isize)
inode_dio_wait(inode);
/* Serialize against page faults */
down_write(&zi->i_mmap_sem);
filemap_invalidate_lock(inode->i_mapping);
/* Serialize against zonefs_iomap_begin() */
mutex_lock(&zi->i_truncate_mutex);
@ -500,7 +500,7 @@ static int zonefs_file_truncate(struct inode *inode, loff_t isize)
unlock:
mutex_unlock(&zi->i_truncate_mutex);
up_write(&zi->i_mmap_sem);
filemap_invalidate_unlock(inode->i_mapping);
return ret;
}
@ -575,18 +575,6 @@ static int zonefs_file_fsync(struct file *file, loff_t start, loff_t end,
return ret;
}
static vm_fault_t zonefs_filemap_fault(struct vm_fault *vmf)
{
struct zonefs_inode_info *zi = ZONEFS_I(file_inode(vmf->vma->vm_file));
vm_fault_t ret;
down_read(&zi->i_mmap_sem);
ret = filemap_fault(vmf);
up_read(&zi->i_mmap_sem);
return ret;
}
static vm_fault_t zonefs_filemap_page_mkwrite(struct vm_fault *vmf)
{
struct inode *inode = file_inode(vmf->vma->vm_file);
@ -607,16 +595,16 @@ static vm_fault_t zonefs_filemap_page_mkwrite(struct vm_fault *vmf)
file_update_time(vmf->vma->vm_file);
/* Serialize against truncates */
down_read(&zi->i_mmap_sem);
filemap_invalidate_lock_shared(inode->i_mapping);
ret = iomap_page_mkwrite(vmf, &zonefs_iomap_ops);
up_read(&zi->i_mmap_sem);
filemap_invalidate_unlock_shared(inode->i_mapping);
sb_end_pagefault(inode->i_sb);
return ret;
}
static const struct vm_operations_struct zonefs_file_vm_ops = {
.fault = zonefs_filemap_fault,
.fault = filemap_fault,
.map_pages = filemap_map_pages,
.page_mkwrite = zonefs_filemap_page_mkwrite,
};
@ -1155,7 +1143,6 @@ static struct inode *zonefs_alloc_inode(struct super_block *sb)
inode_init_once(&zi->i_vnode);
mutex_init(&zi->i_truncate_mutex);
init_rwsem(&zi->i_mmap_sem);
zi->i_wr_refcnt = 0;
return &zi->i_vnode;

7
fs/zonefs/zonefs.h
View File

@ -70,12 +70,11 @@ struct zonefs_inode_info {
* and changes to the inode private data, and in particular changes to
* a sequential file size on completion of direct IO writes.
* Serialization of mmap read IOs with truncate and syscall IO
* operations is done with i_mmap_sem in addition to i_truncate_mutex.
* Only zonefs_seq_file_truncate() takes both lock (i_mmap_sem first,
* i_truncate_mutex second).
* operations is done with invalidate_lock in addition to
* i_truncate_mutex. Only zonefs_seq_file_truncate() takes both lock
* (invalidate_lock first, i_truncate_mutex second).
*/
struct mutex i_truncate_mutex;
struct rw_semaphore i_mmap_sem;
/* guarded by i_truncate_mutex */
unsigned int i_wr_refcnt;

39
include/linux/fs.h
View File

@ -436,6 +436,10 @@ int pagecache_write_end(struct file *, struct address_space *mapping,
* struct address_space - Contents of a cacheable, mappable object.
* @host: Owner, either the inode or the block_device.
* @i_pages: Cached pages.
* @invalidate_lock: Guards coherency between page cache contents and
* file offset->disk block mappings in the filesystem during invalidates.
* It is also used to block modification of page cache contents through
* memory mappings.
* @gfp_mask: Memory allocation flags to use for allocating pages.
* @i_mmap_writable: Number of VM_SHARED mappings.
* @nr_thps: Number of THPs in the pagecache (non-shmem only).
@ -453,6 +457,7 @@ int pagecache_write_end(struct file *, struct address_space *mapping,
struct address_space {
struct inode *host;
struct xarray i_pages;
struct rw_semaphore invalidate_lock;
gfp_t gfp_mask;
atomic_t i_mmap_writable;
#ifdef CONFIG_READ_ONLY_THP_FOR_FS
@ -814,9 +819,42 @@ static inline void inode_lock_shared_nested(struct inode *inode, unsigned subcla
down_read_nested(&inode->i_rwsem, subclass);
}
static inline void filemap_invalidate_lock(struct address_space *mapping)
{
down_write(&mapping->invalidate_lock);
}
static inline void filemap_invalidate_unlock(struct address_space *mapping)
{
up_write(&mapping->invalidate_lock);
}
static inline void filemap_invalidate_lock_shared(struct address_space *mapping)
{
down_read(&mapping->invalidate_lock);
}
static inline int filemap_invalidate_trylock_shared(
struct address_space *mapping)
{
return down_read_trylock(&mapping->invalidate_lock);
}
static inline void filemap_invalidate_unlock_shared(
struct address_space *mapping)
{
up_read(&mapping->invalidate_lock);
}
void lock_two_nondirectories(struct inode *, struct inode*);
void unlock_two_nondirectories(struct inode *, struct inode*);
void filemap_invalidate_lock_two(struct address_space *mapping1,
struct address_space *mapping2);
void filemap_invalidate_unlock_two(struct address_space *mapping1,
struct address_space *mapping2);
/*
* NOTE: in a 32bit arch with a preemptable kernel and
* an UP compile the i_size_read/write must be atomic
@ -2490,6 +2528,7 @@ struct file_system_type {
struct lock_class_key i_lock_key;
struct lock_class_key i_mutex_key;
struct lock_class_key invalidate_lock_key;
struct lock_class_key i_mutex_dir_key;
};

147
mm/filemap.c
View File

@ -76,8 +76,9 @@
* ->swap_lock (exclusive_swap_page, others)
* ->i_pages lock
*
* ->i_mutex
* ->i_mmap_rwsem (truncate->unmap_mapping_range)
* ->i_rwsem
* ->invalidate_lock (acquired by fs in truncate path)
* ->i_mmap_rwsem (truncate->unmap_mapping_range)
*
* ->mmap_lock
* ->i_mmap_rwsem
@ -85,9 +86,10 @@
* ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
*
* ->mmap_lock
* ->lock_page (access_process_vm)
* ->invalidate_lock (filemap_fault)
* ->lock_page (filemap_fault, access_process_vm)
*
* ->i_mutex (generic_perform_write)
* ->i_rwsem (generic_perform_write)
* ->mmap_lock (fault_in_pages_readable->do_page_fault)
*
* bdi->wb.list_lock
@ -1007,6 +1009,44 @@ struct page *__page_cache_alloc(gfp_t gfp)
EXPORT_SYMBOL(__page_cache_alloc);
#endif
/*
* filemap_invalidate_lock_two - lock invalidate_lock for two mappings
*
* Lock exclusively invalidate_lock of any passed mapping that is not NULL.
*
* @mapping1: the first mapping to lock
* @mapping2: the second mapping to lock
*/
void filemap_invalidate_lock_two(struct address_space *mapping1,
struct address_space *mapping2)
{
if (mapping1 > mapping2)
swap(mapping1, mapping2);
if (mapping1)
down_write(&mapping1->invalidate_lock);
if (mapping2 && mapping1 != mapping2)
down_write_nested(&mapping2->invalidate_lock, 1);
}
EXPORT_SYMBOL(filemap_invalidate_lock_two);
/*
* filemap_invalidate_unlock_two - unlock invalidate_lock for two mappings
*
* Unlock exclusive invalidate_lock of any passed mapping that is not NULL.
*
* @mapping1: the first mapping to unlock
* @mapping2: the second mapping to unlock
*/
void filemap_invalidate_unlock_two(struct address_space *mapping1,
struct address_space *mapping2)
{
if (mapping1)
up_write(&mapping1->invalidate_lock);
if (mapping2 && mapping1 != mapping2)
up_write(&mapping2->invalidate_lock);
}
EXPORT_SYMBOL(filemap_invalidate_unlock_two);
/*
* In order to wait for pages to become available there must be
* waitqueues associated with pages. By using a hash table of
@ -2368,20 +2408,30 @@ static int filemap_update_page(struct kiocb *iocb,
{
int error;
if (!trylock_page(page)) {
if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
if (iocb->ki_flags & IOCB_NOWAIT) {
if (!filemap_invalidate_trylock_shared(mapping))
return -EAGAIN;
} else {
filemap_invalidate_lock_shared(mapping);
}
if (!trylock_page(page)) {
error = -EAGAIN;
if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
goto unlock_mapping;
if (!(iocb->ki_flags & IOCB_WAITQ)) {
filemap_invalidate_unlock_shared(mapping);
put_and_wait_on_page_locked(page, TASK_KILLABLE);
return AOP_TRUNCATED_PAGE;
}
error = __lock_page_async(page, iocb->ki_waitq);
if (error)
return error;
goto unlock_mapping;
}
error = AOP_TRUNCATED_PAGE;
if (!page->mapping)
goto truncated;
goto unlock;
error = 0;
if (filemap_range_uptodate(mapping, iocb->ki_pos, iter, page))
@ -2392,15 +2442,13 @@ static int filemap_update_page(struct kiocb *iocb,
goto unlock;
error = filemap_read_page(iocb->ki_filp, mapping, page);
if (error == AOP_TRUNCATED_PAGE)
put_page(page);
return error;
truncated:
unlock_page(page);
put_page(page);
return AOP_TRUNCATED_PAGE;
goto unlock_mapping;
unlock:
unlock_page(page);
unlock_mapping:
filemap_invalidate_unlock_shared(mapping);
if (error == AOP_TRUNCATED_PAGE)
put_page(page);
return error;
}
@ -2415,6 +2463,19 @@ static int filemap_create_page(struct file *file,
if (!page)
return -ENOMEM;
/*
* Protect against truncate / hole punch. Grabbing invalidate_lock here
* assures we cannot instantiate and bring uptodate new pagecache pages
* after evicting page cache during truncate and before actually
* freeing blocks. Note that we could release invalidate_lock after
* inserting the page into page cache as the locked page would then be
* enough to synchronize with hole punching. But there are code paths
* such as filemap_update_page() filling in partially uptodate pages or
* ->readpages() that need to hold invalidate_lock while mapping blocks
* for IO so let's hold the lock here as well to keep locking rules
* simple.
*/
filemap_invalidate_lock_shared(mapping);
error = add_to_page_cache_lru(page, mapping, index,
mapping_gfp_constraint(mapping, GFP_KERNEL));
if (error == -EEXIST)
@ -2426,9 +2487,11 @@ static int filemap_create_page(struct file *file,
if (error)
goto error;
filemap_invalidate_unlock_shared(mapping);
pagevec_add(pvec, page);
return 0;
error:
filemap_invalidate_unlock_shared(mapping);
put_page(page);
return error;
}
@ -2967,6 +3030,7 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
pgoff_t max_off;
struct page *page;
vm_fault_t ret = 0;
bool mapping_locked = false;
max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
if (unlikely(offset >= max_off))
@ -2976,25 +3040,39 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
* Do we have something in the page cache already?
*/
page = find_get_page(mapping, offset);
if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
if (likely(page)) {
/*
* We found the page, so try async readahead before
* waiting for the lock.
* We found the page, so try async readahead before waiting for
* the lock.
*/
fpin = do_async_mmap_readahead(vmf, page);
} else if (!page) {
if (!(vmf->flags & FAULT_FLAG_TRIED))
fpin = do_async_mmap_readahead(vmf, page);
if (unlikely(!PageUptodate(page))) {
filemap_invalidate_lock_shared(mapping);
mapping_locked = true;
}
} else {
/* No page in the page cache at all */
count_vm_event(PGMAJFAULT);
count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
ret = VM_FAULT_MAJOR;
fpin = do_sync_mmap_readahead(vmf);
retry_find:
/*
* See comment in filemap_create_page() why we need
* invalidate_lock
*/
if (!mapping_locked) {
filemap_invalidate_lock_shared(mapping);
mapping_locked = true;
}
page = pagecache_get_page(mapping, offset,
FGP_CREAT|FGP_FOR_MMAP,
vmf->gfp_mask);
if (!page) {
if (fpin)
goto out_retry;
filemap_invalidate_unlock_shared(mapping);
return VM_FAULT_OOM;
}
}
@ -3014,8 +3092,20 @@ retry_find:
* We have a locked page in the page cache, now we need to check
* that it's up-to-date. If not, it is going to be due to an error.
*/
if (unlikely(!PageUptodate(page)))
if (unlikely(!PageUptodate(page))) {
/*
* The page was in cache and uptodate and now it is not.
* Strange but possible since we didn't hold the page lock all
* the time. Let's drop everything get the invalidate lock and
* try again.
*/
if (!mapping_locked) {
unlock_page(page);
put_page(page);
goto retry_find;
}
goto page_not_uptodate;
}
/*
* We've made it this far and we had to drop our mmap_lock, now is the
@ -3026,6 +3116,8 @@ retry_find:
unlock_page(page);
goto out_retry;
}
if (mapping_locked)
filemap_invalidate_unlock_shared(mapping);
/*
* Found the page and have a reference on it.
@ -3056,6 +3148,7 @@ page_not_uptodate:
if (!error || error == AOP_TRUNCATED_PAGE)
goto retry_find;
filemap_invalidate_unlock_shared(mapping);
return VM_FAULT_SIGBUS;
@ -3067,6 +3160,8 @@ out_retry:
*/
if (page)
put_page(page);
if (mapping_locked)
filemap_invalidate_unlock_shared(mapping);
if (fpin)
fput(fpin);
return ret | VM_FAULT_RETRY;
@ -3437,6 +3532,8 @@ out:
*
* If the page does not get brought uptodate, return -EIO.
*
* The function expects mapping->invalidate_lock to be already held.
*
* Return: up to date page on success, ERR_PTR() on failure.
*/
struct page *read_cache_page(struct address_space *mapping,
@ -3460,6 +3557,8 @@ EXPORT_SYMBOL(read_cache_page);
*
* If the page does not get brought uptodate, return -EIO.
*
* The function expects mapping->invalidate_lock to be already held.
*
* Return: up to date page on success, ERR_PTR() on failure.
*/
struct page *read_cache_page_gfp(struct address_space *mapping,
@ -3704,12 +3803,12 @@ EXPORT_SYMBOL(generic_perform_write);
* modification times and calls proper subroutines depending on whether we
* do direct IO or a standard buffered write.
*
* It expects i_mutex to be grabbed unless we work on a block device or similar
* It expects i_rwsem to be grabbed unless we work on a block device or similar
* object which does not need locking at all.
*
* This function does *not* take care of syncing data in case of O_SYNC write.
* A caller has to handle it. This is mainly due to the fact that we want to
* avoid syncing under i_mutex.
* avoid syncing under i_rwsem.
*
* Return:
* * number of bytes written, even for truncated writes
@ -3797,7 +3896,7 @@ EXPORT_SYMBOL(__generic_file_write_iter);
*
* This is a wrapper around __generic_file_write_iter() to be used by most
* filesystems. It takes care of syncing the file in case of O_SYNC file
* and acquires i_mutex as needed.
* and acquires i_rwsem as needed.
* Return:
* * negative error code if no data has been written at all of
* vfs_fsync_range() failed for a synchronous write

2
mm/madvise.c
View File

@ -912,7 +912,7 @@ static long madvise_remove(struct vm_area_struct *vma,
+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
/*
* Filesystem's fallocate may need to take i_mutex. We need to
* Filesystem's fallocate may need to take i_rwsem. We need to
* explicitly grab a reference because the vma (and hence the
* vma's reference to the file) can go away as soon as we drop
* mmap_lock.

2
mm/memory-failure.c
View File

@ -866,7 +866,7 @@ static int me_pagecache_clean(struct page *p, unsigned long pfn)
/*
* Truncation is a bit tricky. Enable it per file system for now.
*
* Open: to take i_mutex or not for this? Right now we don't.
* Open: to take i_rwsem or not for this? Right now we don't.
*/
ret = truncate_error_page(p, pfn, mapping);
out:

2
mm/readahead.c
View File

@ -192,6 +192,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
*/
unsigned int nofs = memalloc_nofs_save();
filemap_invalidate_lock_shared(mapping);
/*
* Preallocate as many pages as we will need.
*/
@ -236,6 +237,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
* will then handle the error.
*/
read_pages(ractl, &page_pool, false);
filemap_invalidate_unlock_shared(mapping);
memalloc_nofs_restore(nofs);
}
EXPORT_SYMBOL_GPL(page_cache_ra_unbounded);

41
mm/rmap.c
View File

@ -20,28 +20,29 @@
/*
* Lock ordering in mm:
*
* inode->i_mutex (while writing or truncating, not reading or faulting)
* inode->i_rwsem (while writing or truncating, not reading or faulting)
* mm->mmap_lock
* page->flags PG_locked (lock_page) * (see huegtlbfs below)
* hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share)
* mapping->i_mmap_rwsem
* hugetlb_fault_mutex (hugetlbfs specific page fault mutex)
* anon_vma->rwsem
* mm->page_table_lock or pte_lock
* swap_lock (in swap_duplicate, swap_info_get)
* mmlist_lock (in mmput, drain_mmlist and others)
* mapping->private_lock (in __set_page_dirty_buffers)
* lock_page_memcg move_lock (in __set_page_dirty_buffers)
* i_pages lock (widely used)
* lruvec->lru_lock (in lock_page_lruvec_irq)
* inode->i_lock (in set_page_dirty's __mark_inode_dirty)
* bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
* sb_lock (within inode_lock in fs/fs-writeback.c)
* i_pages lock (widely used, in set_page_dirty,
* in arch-dependent flush_dcache_mmap_lock,
* within bdi.wb->list_lock in __sync_single_inode)
* mapping->invalidate_lock (in filemap_fault)
* page->flags PG_locked (lock_page) * (see hugetlbfs below)
* hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share)
* mapping->i_mmap_rwsem
* hugetlb_fault_mutex (hugetlbfs specific page fault mutex)
* anon_vma->rwsem
* mm->page_table_lock or pte_lock
* swap_lock (in swap_duplicate, swap_info_get)
* mmlist_lock (in mmput, drain_mmlist and others)
* mapping->private_lock (in __set_page_dirty_buffers)
* lock_page_memcg move_lock (in __set_page_dirty_buffers)
* i_pages lock (widely used)
* lruvec->lru_lock (in lock_page_lruvec_irq)
* inode->i_lock (in set_page_dirty's __mark_inode_dirty)
* bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
* sb_lock (within inode_lock in fs/fs-writeback.c)
* i_pages lock (widely used, in set_page_dirty,
* in arch-dependent flush_dcache_mmap_lock,
* within bdi.wb->list_lock in __sync_single_inode)
*
* anon_vma->rwsem,mapping->i_mutex (memory_failure, collect_procs_anon)
* anon_vma->rwsem,mapping->i_mmap_rwsem (memory_failure, collect_procs_anon)
* ->tasklist_lock
* pte map lock
*

20
mm/shmem.c
View File

@ -96,7 +96,7 @@ static struct vfsmount *shm_mnt;
/*
* shmem_fallocate communicates with shmem_fault or shmem_writepage via
* inode->i_private (with i_mutex making sure that it has only one user at
* inode->i_private (with i_rwsem making sure that it has only one user at
* a time): we would prefer not to enlarge the shmem inode just for that.
*/
struct shmem_falloc {
@ -774,7 +774,7 @@ static int shmem_free_swap(struct address_space *mapping,
* Determine (in bytes) how many of the shmem object's pages mapped by the
* given offsets are swapped out.
*
* This is safe to call without i_mutex or the i_pages lock thanks to RCU,
* This is safe to call without i_rwsem or the i_pages lock thanks to RCU,
* as long as the inode doesn't go away and racy results are not a problem.
*/
unsigned long shmem_partial_swap_usage(struct address_space *mapping,
@ -806,7 +806,7 @@ unsigned long shmem_partial_swap_usage(struct address_space *mapping,
* Determine (in bytes) how many of the shmem object's pages mapped by the
* given vma is swapped out.
*
* This is safe to call without i_mutex or the i_pages lock thanks to RCU,
* This is safe to call without i_rwsem or the i_pages lock thanks to RCU,
* as long as the inode doesn't go away and racy results are not a problem.
*/
unsigned long shmem_swap_usage(struct vm_area_struct *vma)
@ -1069,7 +1069,7 @@ static int shmem_setattr(struct user_namespace *mnt_userns,
loff_t oldsize = inode->i_size;
loff_t newsize = attr->ia_size;
/* protected by i_mutex */
/* protected by i_rwsem */
if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
(newsize > oldsize && (info->seals & F_SEAL_GROW)))
return -EPERM;
@ -2059,7 +2059,7 @@ static vm_fault_t shmem_fault(struct vm_fault *vmf)
/*
* Trinity finds that probing a hole which tmpfs is punching can
* prevent the hole-punch from ever completing: which in turn
* locks writers out with its hold on i_mutex. So refrain from
* locks writers out with its hold on i_rwsem. So refrain from
* faulting pages into the hole while it's being punched. Although
* shmem_undo_range() does remove the additions, it may be unable to
* keep up, as each new page needs its own unmap_mapping_range() call,
@ -2070,7 +2070,7 @@ static vm_fault_t shmem_fault(struct vm_fault *vmf)
* we just need to make racing faults a rare case.
*
* The implementation below would be much simpler if we just used a
* standard mutex or completion: but we cannot take i_mutex in fault,
* standard mutex or completion: but we cannot take i_rwsem in fault,
* and bloating every shmem inode for this unlikely case would be sad.
*/
if (unlikely(inode->i_private)) {
@ -2470,7 +2470,7 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
struct shmem_inode_info *info = SHMEM_I(inode);
pgoff_t index = pos >> PAGE_SHIFT;
/* i_mutex is held by caller */
/* i_rwsem is held by caller */
if (unlikely(info->seals & (F_SEAL_GROW |
F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))) {
if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE))
@ -2570,7 +2570,7 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
/*
* We must evaluate after, since reads (unlike writes)
* are called without i_mutex protection against truncate
* are called without i_rwsem protection against truncate
*/
nr = PAGE_SIZE;
i_size = i_size_read(inode);
@ -2640,7 +2640,7 @@ static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
return -ENXIO;
inode_lock(inode);
/* We're holding i_mutex so we can access i_size directly */
/* We're holding i_rwsem so we can access i_size directly */
offset = mapping_seek_hole_data(mapping, offset, inode->i_size, whence);
if (offset >= 0)
offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
@ -2669,7 +2669,7 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
loff_t unmap_end = round_down(offset + len, PAGE_SIZE) - 1;
DECLARE_WAIT_QUEUE_HEAD_ONSTACK(shmem_falloc_waitq);
/* protected by i_mutex */
/* protected by i_rwsem */
if (info->seals & (F_SEAL_WRITE | F_SEAL_FUTURE_WRITE)) {
error = -EPERM;
goto out;

9
mm/truncate.c
View File

@ -412,7 +412,8 @@ EXPORT_SYMBOL(truncate_inode_pages_range);
* @mapping: mapping to truncate
* @lstart: offset from which to truncate
*
* Called under (and serialised by) inode->i_mutex.
* Called under (and serialised by) inode->i_rwsem and
* mapping->invalidate_lock.
*
* Note: When this function returns, there can be a page in the process of
* deletion (inside __delete_from_page_cache()) in the specified range. Thus
@ -429,7 +430,7 @@ EXPORT_SYMBOL(truncate_inode_pages);
* truncate_inode_pages_final - truncate *all* pages before inode dies
* @mapping: mapping to truncate
*
* Called under (and serialized by) inode->i_mutex.
* Called under (and serialized by) inode->i_rwsem.
*
* Filesystems have to use this in the .evict_inode path to inform the
* VM that this is the final truncate and the inode is going away.
@ -748,7 +749,7 @@ EXPORT_SYMBOL(truncate_pagecache);
* setattr function when ATTR_SIZE is passed in.
*
* Must be called with a lock serializing truncates and writes (generally
* i_mutex but e.g. xfs uses a different lock) and before all filesystem
* i_rwsem but e.g. xfs uses a different lock) and before all filesystem
* specific block truncation has been performed.
*/
void truncate_setsize(struct inode *inode, loff_t newsize)
@ -777,7 +778,7 @@ EXPORT_SYMBOL(truncate_setsize);
*
* The function must be called after i_size is updated so that page fault
* coming after we unlock the page will already see the new i_size.
* The function must be called while we still hold i_mutex - this not only
* The function must be called while we still hold i_rwsem - this not only
* makes sure i_size is stable but also that userspace cannot observe new
* i_size value before we are prepared to store mmap writes at new inode size.
*/