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author | Dmitry Monakhov <dmonakhov@openvz.org> | 2012-10-05 11:31:55 -0400 |
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committer | Theodore Ts'o <tytso@mit.edu> | 2012-10-05 11:31:55 -0400 |
commit | c278531d39f3158bfee93dc67da0b77e09776de2 (patch) | |
tree | b83341e04d54b3f1cd8171f43ec77bbfba06e571 /fs/ext4 | |
parent | 041bbb6d369811e948ae01f3d00414264076be35 (diff) | |
download | linux-3.10-c278531d39f3158bfee93dc67da0b77e09776de2.tar.gz linux-3.10-c278531d39f3158bfee93dc67da0b77e09776de2.tar.bz2 linux-3.10-c278531d39f3158bfee93dc67da0b77e09776de2.zip |
ext4: fix ext4_flush_completed_IO wait semantics
BUG #1) All places where we call ext4_flush_completed_IO are broken
because buffered io and DIO/AIO goes through three stages
1) submitted io,
2) completed io (in i_completed_io_list) conversion pended
3) finished io (conversion done)
And by calling ext4_flush_completed_IO we will flush only
requests which were in (2) stage, which is wrong because:
1) punch_hole and truncate _must_ wait for all outstanding unwritten io
regardless to it's state.
2) fsync and nolock_dio_read should also wait because there is
a time window between end_page_writeback() and ext4_add_complete_io()
As result integrity fsync is broken in case of buffered write
to fallocated region:
fsync blkdev_completion
->filemap_write_and_wait_range
->ext4_end_bio
->end_page_writeback
<-- filemap_write_and_wait_range return
->ext4_flush_completed_IO
sees empty i_completed_io_list but pended
conversion still exist
->ext4_add_complete_io
BUG #2) Race window becomes wider due to the 'ext4: completed_io
locking cleanup V4' patch series
This patch make following changes:
1) ext4_flush_completed_io() now first try to flush completed io and when
wait for any outstanding unwritten io via ext4_unwritten_wait()
2) Rename function to more appropriate name.
3) Assert that all callers of ext4_flush_unwritten_io should hold i_mutex to
prevent endless wait
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/ext4')
-rw-r--r-- | fs/ext4/ext4.h | 3 | ||||
-rw-r--r-- | fs/ext4/extents.c | 6 | ||||
-rw-r--r-- | fs/ext4/file.c | 2 | ||||
-rw-r--r-- | fs/ext4/fsync.c | 2 | ||||
-rw-r--r-- | fs/ext4/indirect.c | 8 | ||||
-rw-r--r-- | fs/ext4/page-io.c | 11 |
6 files changed, 19 insertions, 13 deletions
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 1be2b4472a8..3ab2539b7b2 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1947,7 +1947,7 @@ extern void ext4_htree_free_dir_info(struct dir_private_info *p); /* fsync.c */ extern int ext4_sync_file(struct file *, loff_t, loff_t, int); -extern int ext4_flush_completed_IO(struct inode *); +extern int ext4_flush_unwritten_io(struct inode *); /* hash.c */ extern int ext4fs_dirhash(const char *name, int len, struct @@ -2371,6 +2371,7 @@ extern const struct file_operations ext4_dir_operations; extern const struct inode_operations ext4_file_inode_operations; extern const struct file_operations ext4_file_operations; extern loff_t ext4_llseek(struct file *file, loff_t offset, int origin); +extern void ext4_unwritten_wait(struct inode *inode); /* namei.c */ extern const struct inode_operations ext4_dir_inode_operations; diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index c1fcf489e05..1c94cca35ed 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4268,7 +4268,7 @@ void ext4_ext_truncate(struct inode *inode) * finish any pending end_io work so we won't run the risk of * converting any truncated blocks to initialized later */ - ext4_flush_completed_IO(inode); + ext4_flush_unwritten_io(inode); /* * probably first extent we're gonna free will be last in block @@ -4847,10 +4847,10 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length) /* Wait all existing dio workers, newcomers will block on i_mutex */ ext4_inode_block_unlocked_dio(inode); - inode_dio_wait(inode); - err = ext4_flush_completed_IO(inode); + err = ext4_flush_unwritten_io(inode); if (err) goto out_dio; + inode_dio_wait(inode); credits = ext4_writepage_trans_blocks(inode); handle = ext4_journal_start(inode, credits); diff --git a/fs/ext4/file.c b/fs/ext4/file.c index 39335bda404..ca6f07afe60 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -55,7 +55,7 @@ static int ext4_release_file(struct inode *inode, struct file *filp) return 0; } -static void ext4_unwritten_wait(struct inode *inode) +void ext4_unwritten_wait(struct inode *inode) { wait_queue_head_t *wq = ext4_ioend_wq(inode); diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c index 460000868b8..be1d89f385b 100644 --- a/fs/ext4/fsync.c +++ b/fs/ext4/fsync.c @@ -138,7 +138,7 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync) if (inode->i_sb->s_flags & MS_RDONLY) goto out; - ret = ext4_flush_completed_IO(inode); + ret = ext4_flush_unwritten_io(inode); if (ret < 0) goto out; diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c index 8d849dae842..792e388e7b4 100644 --- a/fs/ext4/indirect.c +++ b/fs/ext4/indirect.c @@ -807,9 +807,11 @@ ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb, retry: if (rw == READ && ext4_should_dioread_nolock(inode)) { - if (unlikely(!list_empty(&ei->i_completed_io_list))) - ext4_flush_completed_IO(inode); - + if (unlikely(atomic_read(&EXT4_I(inode)->i_unwritten))) { + mutex_lock(&inode->i_mutex); + ext4_flush_unwritten_io(inode); + mutex_unlock(&inode->i_mutex); + } /* * Nolock dioread optimization may be dynamically disabled * via ext4_inode_block_unlocked_dio(). Check inode's state diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c index 5b24c407701..68e896e12a6 100644 --- a/fs/ext4/page-io.c +++ b/fs/ext4/page-io.c @@ -189,8 +189,6 @@ static int ext4_do_flush_completed_IO(struct inode *inode, list_add_tail(&io->list, &complete); } - /* It is important to update all flags for all end_io in one shot w/o - * dropping the lock.*/ spin_lock_irqsave(&ei->i_completed_io_lock, flags); while (!list_empty(&complete)) { io = list_entry(complete.next, ext4_io_end_t, list); @@ -228,9 +226,14 @@ static void ext4_end_io_work(struct work_struct *work) ext4_do_flush_completed_IO(io->inode, io); } -int ext4_flush_completed_IO(struct inode *inode) +int ext4_flush_unwritten_io(struct inode *inode) { - return ext4_do_flush_completed_IO(inode, NULL); + int ret; + WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex) && + !(inode->i_state & I_FREEING)); + ret = ext4_do_flush_completed_IO(inode, NULL); + ext4_unwritten_wait(inode); + return ret; } ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags) |