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ceph: track read contexts in ceph_file_info 

Previously ceph_read_iter() uses current->journal to pass context info
to ceph_readpages(), so that ceph_readpages() can distinguish read(2)
from readahead(2)/fadvise(2)/madvise(2). The problem is that page fault
can happen when copying data to userspace memory. Page fault may call
other filesystem's page_mkwrite() if the userspace memory is mapped to a
file. The later filesystem may also want to use current->journal.

The fix is define a on-stack data structure in ceph_read_iter(), add it
to context list in ceph_file_info. ceph_readpages() searches the list,
find if there is a context belongs to current thread.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Yan, Zheng 2017-12-15 11:15:36 +08:00 committed by Ilya Dryomov
parent 5495c2d04f
commit 5d98830828
3 changed files with 66 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
fs/ceph/addr.c
View File

@ -299,7 +299,8 @@ unlock:
* start an async read(ahead) operation. return nr_pages we submitted
* a read for on success, or negative error code.
*/
static int start_read(struct inode *inode, struct list_head *page_list, int max)
static int start_read(struct inode *inode, struct ceph_rw_context *rw_ctx,
struct list_head *page_list, int max)
{
struct ceph_osd_client *osdc =
&ceph_inode_to_client(inode)->client->osdc;
@ -316,7 +317,7 @@ static int start_read(struct inode *inode, struct list_head *page_list, int max)
int got = 0;
int ret = 0;
if (!current->journal_info) {
if (!rw_ctx) {
/* caller of readpages does not hold buffer and read caps
* (fadvise, madvise and readahead cases) */
int want = CEPH_CAP_FILE_CACHE;
@ -437,6 +438,8 @@ static int ceph_readpages(struct file *file, struct address_space *mapping,
{
struct inode *inode = file_inode(file);
struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
struct ceph_file_info *ci = file->private_data;
struct ceph_rw_context *rw_ctx;
int rc = 0;
int max = 0;
@ -449,11 +452,12 @@ static int ceph_readpages(struct file *file, struct address_space *mapping,
if (rc == 0)
goto out;
rw_ctx = ceph_find_rw_context(ci);
max = fsc->mount_options->rsize >> PAGE_SHIFT;
dout("readpages %p file %p nr_pages %d max %d\n",
inode, file, nr_pages, max);
dout("readpages %p file %p ctx %p nr_pages %d max %d\n",
inode, file, rw_ctx, nr_pages, max);
while (!list_empty(page_list)) {
rc = start_read(inode, page_list, max);
rc = start_read(inode, rw_ctx, page_list, max);
if (rc < 0)
goto out;
}
@ -1450,9 +1454,10 @@ static int ceph_filemap_fault(struct vm_fault *vmf)
if ((got & (CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO)) ||
ci->i_inline_version == CEPH_INLINE_NONE) {
current->journal_info = vma->vm_file;
CEPH_DEFINE_RW_CONTEXT(rw_ctx, got);
ceph_add_rw_context(fi, &rw_ctx);
ret = filemap_fault(vmf);
current->journal_info = NULL;
ceph_del_rw_context(fi, &rw_ctx);
} else
ret = -EAGAIN;

10
fs/ceph/file.c
View File

@ -181,6 +181,10 @@ static int ceph_init_file(struct inode *inode, struct file *file, int fmode)
return -ENOMEM;
}
cf->fmode = fmode;
spin_lock_init(&cf->rw_contexts_lock);
INIT_LIST_HEAD(&cf->rw_contexts);
cf->next_offset = 2;
cf->readdir_cache_idx = -1;
file->private_data = cf;
@ -464,6 +468,7 @@ int ceph_release(struct inode *inode, struct file *file)
ceph_mdsc_put_request(cf->last_readdir);
kfree(cf->last_name);
kfree(cf->dir_info);
WARN_ON(!list_empty(&cf->rw_contexts));
kmem_cache_free(ceph_file_cachep, cf);
/* wake up anyone waiting for caps on this inode */
@ -1199,12 +1204,13 @@ again:
retry_op = READ_INLINE;
}
} else {
CEPH_DEFINE_RW_CONTEXT(rw_ctx, got);
dout("aio_read %p %llx.%llx %llu~%u got cap refs on %s\n",
inode, ceph_vinop(inode), iocb->ki_pos, (unsigned)len,
ceph_cap_string(got));
current->journal_info = filp;
ceph_add_rw_context(fi, &rw_ctx);
ret = generic_file_read_iter(iocb, to);
current->journal_info = NULL;
ceph_del_rw_context(fi, &rw_ctx);
}
dout("aio_read %p %llx.%llx dropping cap refs on %s = %d\n",
inode, ceph_vinop(inode), ceph_cap_string(got), (int)ret);

46
fs/ceph/super.h
View File

@ -669,6 +669,9 @@ struct ceph_file_info {
short fmode; /* initialized on open */
short flags; /* CEPH_F_* */
spinlock_t rw_contexts_lock;
struct list_head rw_contexts;
/* readdir: position within the dir */
u32 frag;
struct ceph_mds_request *last_readdir;
@ -685,6 +688,49 @@ struct ceph_file_info {
int dir_info_len;
};
struct ceph_rw_context {
struct list_head list;
struct task_struct *thread;
int caps;
};
#define CEPH_DEFINE_RW_CONTEXT(_name, _caps) \
struct ceph_rw_context _name = { \
.thread = current, \
.caps = _caps, \
}
static inline void ceph_add_rw_context(struct ceph_file_info *cf,
struct ceph_rw_context *ctx)
{
spin_lock(&cf->rw_contexts_lock);
list_add(&ctx->list, &cf->rw_contexts);
spin_unlock(&cf->rw_contexts_lock);
}
static inline void ceph_del_rw_context(struct ceph_file_info *cf,
struct ceph_rw_context *ctx)
{
spin_lock(&cf->rw_contexts_lock);
list_del(&ctx->list);
spin_unlock(&cf->rw_contexts_lock);
}
static inline struct ceph_rw_context*
ceph_find_rw_context(struct ceph_file_info *cf)
{
struct ceph_rw_context *ctx, *found = NULL;
spin_lock(&cf->rw_contexts_lock);
list_for_each_entry(ctx, &cf->rw_contexts, list) {
if (ctx->thread == current) {
found = ctx;
break;
}
}
spin_unlock(&cf->rw_contexts_lock);
return found;
}
struct ceph_readdir_cache_control {
struct page *page;
struct dentry **dentries;