ext4: use i_mutex to serialize unaligned AIO DIO

Currently we've used hashed aio_mutex to serialize unaligned AIO DIO.
However the code cleanups that happened after 2011 when the lock was
introduced made aio_mutex acquired at almost the same places where we
already have exclusion using i_mutex. So just use i_mutex for the
exclusion of unaligned AIO DIO.

The change moves waiting for pending unwritten extent conversion under
i_mutex. That makes special handling of O_APPEND writes unnecessary and
also avoids possible livelocking of unaligned AIO DIO with aligned one
(nothing was preventing contiguous stream of aligned AIO DIOs to let
unaligned AIO DIO wait forever).

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 1 insertions, 4 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 2f550519e0aa..4d5756024e98 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5321,7 +5321,6 @@ MODULE_ALIAS_FS("ext4");
 
 /* Shared across all ext4 file systems */
 wait_queue_head_t ext4__ioend_wq[EXT4_WQ_HASH_SZ];
-struct mutex ext4__aio_mutex[EXT4_WQ_HASH_SZ];
 
 static int __init ext4_init_fs(void)
 {
@@ -5334,10 +5333,8 @@ static int __init ext4_init_fs(void)
         /* Build-time check for flags consistency */
         ext4_check_flag_values();
 
-        for (i = 0; i < EXT4_WQ_HASH_SZ; i++) {
-                mutex_init(&ext4__aio_mutex[i]);
+        for (i = 0; i < EXT4_WQ_HASH_SZ; i++)
                 init_waitqueue_head(&ext4__ioend_wq[i]);
-        }
 
         err = ext4_init_es();
         if (err)