path: root/fs/ext4/ext4.h
diff options
authorDmitry Monakhov <dmonakhov@openvz.org>2012-10-05 11:31:55 -0400
committerTheodore Ts'o <tytso@mit.edu>2012-10-05 11:31:55 -0400
commitc278531d39f3158bfee93dc67da0b77e09776de2 (patch)
treeb83341e04d54b3f1cd8171f43ec77bbfba06e571 /fs/ext4/ext4.h
parent041bbb6d369811e948ae01f3d00414264076be35 (diff)
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/ext4.h')
1 files changed, 2 insertions, 1 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;