585 lines
24 KiB
Plaintext
585 lines
24 KiB
Plaintext
The text below describes the locking rules for VFS-related methods.
|
|
It is (believed to be) up-to-date. *Please*, if you change anything in
|
|
prototypes or locking protocols - update this file. And update the relevant
|
|
instances in the tree, don't leave that to maintainers of filesystems/devices/
|
|
etc. At the very least, put the list of dubious cases in the end of this file.
|
|
Don't turn it into log - maintainers of out-of-the-tree code are supposed to
|
|
be able to use diff(1).
|
|
Thing currently missing here: socket operations. Alexey?
|
|
|
|
--------------------------- dentry_operations --------------------------
|
|
prototypes:
|
|
int (*d_revalidate)(struct dentry *, unsigned int);
|
|
int (*d_weak_revalidate)(struct dentry *, unsigned int);
|
|
int (*d_hash)(const struct dentry *, struct qstr *);
|
|
int (*d_compare)(const struct dentry *,
|
|
unsigned int, const char *, const struct qstr *);
|
|
int (*d_delete)(struct dentry *);
|
|
int (*d_init)(struct dentry *);
|
|
void (*d_release)(struct dentry *);
|
|
void (*d_iput)(struct dentry *, struct inode *);
|
|
char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen);
|
|
struct vfsmount *(*d_automount)(struct path *path);
|
|
int (*d_manage)(const struct path *, bool);
|
|
struct dentry *(*d_real)(struct dentry *, const struct inode *,
|
|
unsigned int, unsigned int);
|
|
|
|
locking rules:
|
|
rename_lock ->d_lock may block rcu-walk
|
|
d_revalidate: no no yes (ref-walk) maybe
|
|
d_weak_revalidate:no no yes no
|
|
d_hash no no no maybe
|
|
d_compare: yes no no maybe
|
|
d_delete: no yes no no
|
|
d_init: no no yes no
|
|
d_release: no no yes no
|
|
d_prune: no yes no no
|
|
d_iput: no no yes no
|
|
d_dname: no no no no
|
|
d_automount: no no yes no
|
|
d_manage: no no yes (ref-walk) maybe
|
|
d_real no no yes no
|
|
|
|
--------------------------- inode_operations ---------------------------
|
|
prototypes:
|
|
int (*create) (struct inode *,struct dentry *,umode_t, bool);
|
|
struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
|
|
int (*link) (struct dentry *,struct inode *,struct dentry *);
|
|
int (*unlink) (struct inode *,struct dentry *);
|
|
int (*symlink) (struct inode *,struct dentry *,const char *);
|
|
int (*mkdir) (struct inode *,struct dentry *,umode_t);
|
|
int (*rmdir) (struct inode *,struct dentry *);
|
|
int (*mknod) (struct inode *,struct dentry *,umode_t,dev_t);
|
|
int (*rename) (struct inode *, struct dentry *,
|
|
struct inode *, struct dentry *, unsigned int);
|
|
int (*readlink) (struct dentry *, char __user *,int);
|
|
const char *(*get_link) (struct dentry *, struct inode *, void **);
|
|
void (*truncate) (struct inode *);
|
|
int (*permission) (struct inode *, int, unsigned int);
|
|
int (*get_acl)(struct inode *, int);
|
|
int (*setattr) (struct dentry *, struct iattr *);
|
|
int (*getattr) (const struct path *, struct kstat *, u32, unsigned int);
|
|
ssize_t (*listxattr) (struct dentry *, char *, size_t);
|
|
int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start, u64 len);
|
|
void (*update_time)(struct inode *, struct timespec *, int);
|
|
int (*atomic_open)(struct inode *, struct dentry *,
|
|
struct file *, unsigned open_flag,
|
|
umode_t create_mode, int *opened);
|
|
int (*tmpfile) (struct inode *, struct dentry *, umode_t);
|
|
|
|
locking rules:
|
|
all may block
|
|
i_mutex(inode)
|
|
lookup: yes
|
|
create: yes
|
|
link: yes (both)
|
|
mknod: yes
|
|
symlink: yes
|
|
mkdir: yes
|
|
unlink: yes (both)
|
|
rmdir: yes (both) (see below)
|
|
rename: yes (all) (see below)
|
|
readlink: no
|
|
get_link: no
|
|
setattr: yes
|
|
permission: no (may not block if called in rcu-walk mode)
|
|
get_acl: no
|
|
getattr: no
|
|
listxattr: no
|
|
fiemap: no
|
|
update_time: no
|
|
atomic_open: yes
|
|
tmpfile: no
|
|
|
|
|
|
Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on
|
|
victim.
|
|
cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem.
|
|
|
|
See Documentation/filesystems/directory-locking for more detailed discussion
|
|
of the locking scheme for directory operations.
|
|
|
|
----------------------- xattr_handler operations -----------------------
|
|
prototypes:
|
|
bool (*list)(struct dentry *dentry);
|
|
int (*get)(const struct xattr_handler *handler, struct dentry *dentry,
|
|
struct inode *inode, const char *name, void *buffer,
|
|
size_t size);
|
|
int (*set)(const struct xattr_handler *handler, struct dentry *dentry,
|
|
struct inode *inode, const char *name, const void *buffer,
|
|
size_t size, int flags);
|
|
|
|
locking rules:
|
|
all may block
|
|
i_mutex(inode)
|
|
list: no
|
|
get: no
|
|
set: yes
|
|
|
|
--------------------------- super_operations ---------------------------
|
|
prototypes:
|
|
struct inode *(*alloc_inode)(struct super_block *sb);
|
|
void (*destroy_inode)(struct inode *);
|
|
void (*dirty_inode) (struct inode *, int flags);
|
|
int (*write_inode) (struct inode *, struct writeback_control *wbc);
|
|
int (*drop_inode) (struct inode *);
|
|
void (*evict_inode) (struct inode *);
|
|
void (*put_super) (struct super_block *);
|
|
int (*sync_fs)(struct super_block *sb, int wait);
|
|
int (*freeze_fs) (struct super_block *);
|
|
int (*unfreeze_fs) (struct super_block *);
|
|
int (*statfs) (struct dentry *, struct kstatfs *);
|
|
int (*remount_fs) (struct super_block *, int *, char *);
|
|
void (*umount_begin) (struct super_block *);
|
|
int (*show_options)(struct seq_file *, struct dentry *);
|
|
ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
|
|
ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
|
|
int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
|
|
|
|
locking rules:
|
|
All may block [not true, see below]
|
|
s_umount
|
|
alloc_inode:
|
|
destroy_inode:
|
|
dirty_inode:
|
|
write_inode:
|
|
drop_inode: !!!inode->i_lock!!!
|
|
evict_inode:
|
|
put_super: write
|
|
sync_fs: read
|
|
freeze_fs: write
|
|
unfreeze_fs: write
|
|
statfs: maybe(read) (see below)
|
|
remount_fs: write
|
|
umount_begin: no
|
|
show_options: no (namespace_sem)
|
|
quota_read: no (see below)
|
|
quota_write: no (see below)
|
|
bdev_try_to_free_page: no (see below)
|
|
|
|
->statfs() has s_umount (shared) when called by ustat(2) (native or
|
|
compat), but that's an accident of bad API; s_umount is used to pin
|
|
the superblock down when we only have dev_t given us by userland to
|
|
identify the superblock. Everything else (statfs(), fstatfs(), etc.)
|
|
doesn't hold it when calling ->statfs() - superblock is pinned down
|
|
by resolving the pathname passed to syscall.
|
|
->quota_read() and ->quota_write() functions are both guaranteed to
|
|
be the only ones operating on the quota file by the quota code (via
|
|
dqio_sem) (unless an admin really wants to screw up something and
|
|
writes to quota files with quotas on). For other details about locking
|
|
see also dquot_operations section.
|
|
->bdev_try_to_free_page is called from the ->releasepage handler of
|
|
the block device inode. See there for more details.
|
|
|
|
--------------------------- file_system_type ---------------------------
|
|
prototypes:
|
|
struct dentry *(*mount) (struct file_system_type *, int,
|
|
const char *, void *);
|
|
void (*kill_sb) (struct super_block *);
|
|
locking rules:
|
|
may block
|
|
mount yes
|
|
kill_sb yes
|
|
|
|
->mount() returns ERR_PTR or the root dentry; its superblock should be locked
|
|
on return.
|
|
->kill_sb() takes a write-locked superblock, does all shutdown work on it,
|
|
unlocks and drops the reference.
|
|
|
|
--------------------------- address_space_operations --------------------------
|
|
prototypes:
|
|
int (*writepage)(struct page *page, struct writeback_control *wbc);
|
|
int (*readpage)(struct file *, struct page *);
|
|
int (*writepages)(struct address_space *, struct writeback_control *);
|
|
int (*set_page_dirty)(struct page *page);
|
|
int (*readpages)(struct file *filp, struct address_space *mapping,
|
|
struct list_head *pages, unsigned nr_pages);
|
|
int (*write_begin)(struct file *, struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned flags,
|
|
struct page **pagep, void **fsdata);
|
|
int (*write_end)(struct file *, struct address_space *mapping,
|
|
loff_t pos, unsigned len, unsigned copied,
|
|
struct page *page, void *fsdata);
|
|
sector_t (*bmap)(struct address_space *, sector_t);
|
|
void (*invalidatepage) (struct page *, unsigned int, unsigned int);
|
|
int (*releasepage) (struct page *, int);
|
|
void (*freepage)(struct page *);
|
|
int (*direct_IO)(struct kiocb *, struct iov_iter *iter);
|
|
bool (*isolate_page) (struct page *, isolate_mode_t);
|
|
int (*migratepage)(struct address_space *, struct page *, struct page *);
|
|
void (*putback_page) (struct page *);
|
|
int (*launder_page)(struct page *);
|
|
int (*is_partially_uptodate)(struct page *, unsigned long, unsigned long);
|
|
int (*error_remove_page)(struct address_space *, struct page *);
|
|
int (*swap_activate)(struct file *);
|
|
int (*swap_deactivate)(struct file *);
|
|
|
|
locking rules:
|
|
All except set_page_dirty and freepage may block
|
|
|
|
PageLocked(page) i_mutex
|
|
writepage: yes, unlocks (see below)
|
|
readpage: yes, unlocks
|
|
writepages:
|
|
set_page_dirty no
|
|
readpages:
|
|
write_begin: locks the page yes
|
|
write_end: yes, unlocks yes
|
|
bmap:
|
|
invalidatepage: yes
|
|
releasepage: yes
|
|
freepage: yes
|
|
direct_IO:
|
|
isolate_page: yes
|
|
migratepage: yes (both)
|
|
putback_page: yes
|
|
launder_page: yes
|
|
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).
|
|
|
|
->readpage() unlocks the page, either synchronously or via I/O
|
|
completion.
|
|
|
|
->readpages() populates the pagecache with the passed pages and starts
|
|
I/O against them. They come unlocked upon I/O completion.
|
|
|
|
->writepage() is used for two purposes: for "memory cleansing" and for
|
|
"sync". These are quite different operations and the behaviour may differ
|
|
depending upon the mode.
|
|
|
|
If writepage is called for sync (wbc->sync_mode != WBC_SYNC_NONE) then
|
|
it *must* start I/O against the page, even if that would involve
|
|
blocking on in-progress I/O.
|
|
|
|
If writepage is called for memory cleansing (sync_mode ==
|
|
WBC_SYNC_NONE) then its role is to get as much writeout underway as
|
|
possible. So writepage should try to avoid blocking against
|
|
currently-in-progress I/O.
|
|
|
|
If the filesystem is not called for "sync" and it determines that it
|
|
would need to block against in-progress I/O to be able to start new I/O
|
|
against the page the filesystem should redirty the page with
|
|
redirty_page_for_writepage(), then unlock the page and return zero.
|
|
This may also be done to avoid internal deadlocks, but rarely.
|
|
|
|
If the filesystem is called for sync then it must wait on any
|
|
in-progress I/O and then start new I/O.
|
|
|
|
The filesystem should unlock the page synchronously, before returning to the
|
|
caller, unless ->writepage() returns special WRITEPAGE_ACTIVATE
|
|
value. WRITEPAGE_ACTIVATE means that page cannot really be written out
|
|
currently, and VM should stop calling ->writepage() on this page for some
|
|
time. VM does this by moving page to the head of the active list, hence the
|
|
name.
|
|
|
|
Unless the filesystem is going to redirty_page_for_writepage(), unlock the page
|
|
and return zero, writepage *must* run set_page_writeback() against the page,
|
|
followed by unlocking it. Once set_page_writeback() has been run against the
|
|
page, write I/O can be submitted and the write I/O completion handler must run
|
|
end_page_writeback() once the I/O is complete. If no I/O is submitted, the
|
|
filesystem must run end_page_writeback() against the page before returning from
|
|
writepage.
|
|
|
|
That is: after 2.5.12, pages which are under writeout are *not* locked. Note,
|
|
if the filesystem needs the page to be locked during writeout, that is ok, too,
|
|
the page is allowed to be unlocked at any point in time between the calls to
|
|
set_page_writeback() and end_page_writeback().
|
|
|
|
Note, failure to run either redirty_page_for_writepage() or the combination of
|
|
set_page_writeback()/end_page_writeback() on a page submitted to writepage
|
|
will leave the page itself marked clean but it will be tagged as dirty in the
|
|
radix tree. This incoherency can lead to all sorts of hard-to-debug problems
|
|
in the filesystem like having dirty inodes at umount and losing written data.
|
|
|
|
->writepages() is used for periodic writeback and for syscall-initiated
|
|
sync operations. The address_space should start I/O against at least
|
|
*nr_to_write pages. *nr_to_write must be decremented for each page which is
|
|
written. The address_space implementation may write more (or less) pages
|
|
than *nr_to_write asks for, but it should try to be reasonably close. If
|
|
nr_to_write is NULL, all dirty pages must be written.
|
|
|
|
writepages should _only_ write pages which are present on
|
|
mapping->io_pages.
|
|
|
|
->set_page_dirty() is called from various places in the kernel
|
|
when the target page is marked as needing writeback. It may be called
|
|
under spinlock (it cannot block) and is sometimes called with the page
|
|
not locked.
|
|
|
|
->bmap() is currently used by legacy ioctl() (FIBMAP) provided by some
|
|
filesystems and by the swapper. The latter will eventually go away. Please,
|
|
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.
|
|
|
|
->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
|
|
indicate that the buffers are (or may be) freeable. If ->releasepage is zero,
|
|
the kernel assumes that the fs has no private interest in the buffers.
|
|
|
|
->freepage() is called when the kernel is done dropping the page
|
|
from the page cache.
|
|
|
|
->launder_page() may be called prior to releasing a page if
|
|
it is still found to be dirty. It returns zero if the page was successfully
|
|
cleaned, or an error value if not. Note that in order to prevent the page
|
|
getting mapped back in and redirtied, it needs to be kept locked
|
|
across the entire operation.
|
|
|
|
->swap_activate will be called with a non-zero argument on
|
|
files backing (non block device backed) swapfiles. A return value
|
|
of zero indicates success, in which case this file can be used for
|
|
backing swapspace. The swapspace operations will be proxied to the
|
|
address space operations.
|
|
|
|
->swap_deactivate() will be called in the sys_swapoff()
|
|
path after ->swap_activate() returned success.
|
|
|
|
----------------------- file_lock_operations ------------------------------
|
|
prototypes:
|
|
void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
|
|
void (*fl_release_private)(struct file_lock *);
|
|
|
|
|
|
locking rules:
|
|
inode->i_lock may block
|
|
fl_copy_lock: yes no
|
|
fl_release_private: maybe maybe[1]
|
|
|
|
[1]: ->fl_release_private for flock or POSIX locks is currently allowed
|
|
to block. Leases however can still be freed while the i_lock is held and
|
|
so fl_release_private called on a lease should not block.
|
|
|
|
----------------------- lock_manager_operations ---------------------------
|
|
prototypes:
|
|
int (*lm_compare_owner)(struct file_lock *, struct file_lock *);
|
|
unsigned long (*lm_owner_key)(struct file_lock *);
|
|
void (*lm_notify)(struct file_lock *); /* unblock callback */
|
|
int (*lm_grant)(struct file_lock *, struct file_lock *, int);
|
|
void (*lm_break)(struct file_lock *); /* break_lease callback */
|
|
int (*lm_change)(struct file_lock **, int);
|
|
|
|
locking rules:
|
|
|
|
inode->i_lock blocked_lock_lock may block
|
|
lm_compare_owner: yes[1] maybe no
|
|
lm_owner_key yes[1] yes no
|
|
lm_notify: yes yes no
|
|
lm_grant: no no no
|
|
lm_break: yes no no
|
|
lm_change yes no no
|
|
|
|
[1]: ->lm_compare_owner and ->lm_owner_key are generally called with
|
|
*an* inode->i_lock held. It may not be the i_lock of the inode
|
|
associated with either file_lock argument! This is the case with deadlock
|
|
detection, since the code has to chase down the owners of locks that may
|
|
be entirely unrelated to the one on which the lock is being acquired.
|
|
For deadlock detection however, the blocked_lock_lock is also held. The
|
|
fact that these locks are held ensures that the file_locks do not
|
|
disappear out from under you while doing the comparison or generating an
|
|
owner key.
|
|
|
|
--------------------------- buffer_head -----------------------------------
|
|
prototypes:
|
|
void (*b_end_io)(struct buffer_head *bh, int uptodate);
|
|
|
|
locking rules:
|
|
called from interrupts. In other words, extreme care is needed here.
|
|
bh is locked, but that's all warranties we have here. Currently only RAID1,
|
|
highmem, fs/buffer.c, and fs/ntfs/aops.c are providing these. Block devices
|
|
call this method upon the IO completion.
|
|
|
|
--------------------------- block_device_operations -----------------------
|
|
prototypes:
|
|
int (*open) (struct block_device *, fmode_t);
|
|
int (*release) (struct gendisk *, fmode_t);
|
|
int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
|
|
int (*compat_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);
|
|
int (*direct_access) (struct block_device *, sector_t, void **,
|
|
unsigned long *);
|
|
int (*media_changed) (struct gendisk *);
|
|
void (*unlock_native_capacity) (struct gendisk *);
|
|
int (*revalidate_disk) (struct gendisk *);
|
|
int (*getgeo)(struct block_device *, struct hd_geometry *);
|
|
void (*swap_slot_free_notify) (struct block_device *, unsigned long);
|
|
|
|
locking rules:
|
|
bd_mutex
|
|
open: yes
|
|
release: yes
|
|
ioctl: no
|
|
compat_ioctl: no
|
|
direct_access: no
|
|
media_changed: no
|
|
unlock_native_capacity: no
|
|
revalidate_disk: no
|
|
getgeo: no
|
|
swap_slot_free_notify: no (see below)
|
|
|
|
media_changed, unlock_native_capacity and revalidate_disk are called only from
|
|
check_disk_change().
|
|
|
|
swap_slot_free_notify is called with swap_lock and sometimes the page lock
|
|
held.
|
|
|
|
|
|
--------------------------- file_operations -------------------------------
|
|
prototypes:
|
|
loff_t (*llseek) (struct file *, loff_t, int);
|
|
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
|
|
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 (*iterate) (struct file *, struct dir_context *);
|
|
unsigned int (*poll) (struct file *, struct poll_table_struct *);
|
|
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
|
|
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
|
|
int (*mmap) (struct file *, struct vm_area_struct *);
|
|
int (*open) (struct inode *, struct file *);
|
|
int (*flush) (struct file *);
|
|
int (*release) (struct inode *, struct file *);
|
|
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,
|
|
unsigned long, unsigned long, unsigned long);
|
|
int (*check_flags)(int);
|
|
int (*flock) (struct file *, int, struct file_lock *);
|
|
ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *,
|
|
size_t, unsigned int);
|
|
ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *,
|
|
size_t, unsigned int);
|
|
int (*setlease)(struct file *, long, struct file_lock **, void **);
|
|
long (*fallocate)(struct file *, int, loff_t, loff_t);
|
|
};
|
|
|
|
locking rules:
|
|
All may block.
|
|
|
|
->llseek() locking has moved from llseek to the individual llseek
|
|
implementations. If your fs is not using generic_file_llseek, you
|
|
need to acquire and release the appropriate locks in your ->llseek().
|
|
For many filesystems, it is probably safe to acquire the inode
|
|
mutex or just to use i_size_read() instead.
|
|
Note: this does not protect the file->f_pos against concurrent modifications
|
|
since this is something the userspace has to take care about.
|
|
|
|
->fasync() is responsible for maintaining the FASYNC bit in filp->f_flags.
|
|
Most instances call fasync_helper(), which does that maintenance, so it's
|
|
not normally something one needs to worry about. Return values > 0 will be
|
|
mapped to zero in the VFS layer.
|
|
|
|
->readdir() and ->ioctl() on directories must be changed. Ideally we would
|
|
move ->readdir() to inode_operations and use a separate method for directory
|
|
->ioctl() or kill the latter completely. One of the problems is that for
|
|
anything that resembles union-mount we won't have a struct file for all
|
|
components. And there are other reasons why the current interface is a mess...
|
|
|
|
->read on directories probably must go away - we should just enforce -EISDIR
|
|
in sys_read() and friends.
|
|
|
|
->setlease operations should call generic_setlease() before or after setting
|
|
the lease within the individual filesystem to record the result of the
|
|
operation
|
|
|
|
--------------------------- dquot_operations -------------------------------
|
|
prototypes:
|
|
int (*write_dquot) (struct dquot *);
|
|
int (*acquire_dquot) (struct dquot *);
|
|
int (*release_dquot) (struct dquot *);
|
|
int (*mark_dirty) (struct dquot *);
|
|
int (*write_info) (struct super_block *, int);
|
|
|
|
These operations are intended to be more or less wrapping functions that ensure
|
|
a proper locking wrt the filesystem and call the generic quota operations.
|
|
|
|
What filesystem should expect from the generic quota functions:
|
|
|
|
FS recursion Held locks when called
|
|
write_dquot: yes dqonoff_sem or dqptr_sem
|
|
acquire_dquot: yes dqonoff_sem or dqptr_sem
|
|
release_dquot: yes dqonoff_sem or dqptr_sem
|
|
mark_dirty: no -
|
|
write_info: yes dqonoff_sem
|
|
|
|
FS recursion means calling ->quota_read() and ->quota_write() from superblock
|
|
operations.
|
|
|
|
More details about quota locking can be found in fs/dquot.c.
|
|
|
|
--------------------------- vm_operations_struct -----------------------------
|
|
prototypes:
|
|
void (*open)(struct vm_area_struct*);
|
|
void (*close)(struct vm_area_struct*);
|
|
int (*fault)(struct vm_area_struct*, struct vm_fault *);
|
|
int (*page_mkwrite)(struct vm_area_struct *, struct vm_fault *);
|
|
int (*pfn_mkwrite)(struct vm_area_struct *, struct vm_fault *);
|
|
int (*access)(struct vm_area_struct *, unsigned long, void*, int, int);
|
|
|
|
locking rules:
|
|
mmap_sem PageLocked(page)
|
|
open: yes
|
|
close: yes
|
|
fault: yes can return with page locked
|
|
map_pages: yes
|
|
page_mkwrite: yes can return with page locked
|
|
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
|
|
subsequent truncate), and then return with VM_FAULT_LOCKED, and the page
|
|
locked. The VM will unlock the page.
|
|
|
|
->map_pages() is called when VM asks to map easy accessible pages.
|
|
Filesystem should find and map pages associated with offsets from "start_pgoff"
|
|
till "end_pgoff". ->map_pages() is called with page table locked and must
|
|
not block. If it's not possible to reach a page without blocking,
|
|
filesystem should skip it. Filesystem should use do_set_pte() to setup
|
|
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.
|
|
|
|
->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
|
|
VM_FAULT_NOPAGE. Or one of the VM_FAULT_ERROR types. The default behavior
|
|
after this call is to make the pte read-write, unless pfn_mkwrite returns
|
|
an error.
|
|
|
|
->access() is called when get_user_pages() fails in
|
|
access_process_vm(), typically used to debug a process through
|
|
/proc/pid/mem or ptrace. This function is needed only for
|
|
VM_IO | VM_PFNMAP VMAs.
|
|
|
|
================================================================================
|
|
Dubious stuff
|
|
|
|
(if you break something or notice that it is broken and do not fix it yourself
|
|
- at least put it here)
|