We were using shared locking only in case of dioread_nolock mount option in case
of DIO overwrites. This mount condition is not needed anymore with current code,
since:-
1. No race between buffered writes & DIO overwrites. Since buffIO writes takes
exclusive lock & DIO overwrites will take shared locking. Also DIO path will
make sure to flush and wait for any dirty page cache data.
2. No race between buffered reads & DIO overwrites, since there is no block
allocation that is possible with DIO overwrites. So no stale data exposure
should happen. Same is the case between DIO reads & DIO overwrites.
3. Also other paths like truncate is protected, since we wait there for any DIO
in flight to be over.
Reviewed-by: Jan Kara <jack@xxxxxxx>
Tested-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
Signed-off-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
---
fs/ext4/file.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 1da49dffa3df..9c2711bce0f9 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -392,8 +392,8 @@ static const struct iomap_dio_ops ext4_dio_write_ops = {
* - For extending writes case we don't take the shared lock, since it requires
* updating inode i_disksize and/or orphan handling with exclusive lock.
*
- * - shared locking will only be true mostly with overwrites in dioread_nolock
- * mode. Otherwise we will switch to exclusive i_rwsem lock.
+ * - shared locking will only be true mostly with overwrites. Otherwise we will
+ * switch to exclusive i_rwsem lock.
*/
static ssize_t ext4_dio_write_checks(struct kiocb *iocb, struct iov_iter *from,
bool *ilock_shared, bool *extend)
@@ -415,14 +415,11 @@ static ssize_t ext4_dio_write_checks(struct kiocb *iocb, struct iov_iter *from,
*extend = true;
/*
* Determine whether the IO operation will overwrite allocated
- * and initialized blocks. If so, check to see whether it is
- * possible to take the dioread_nolock path.
- *
+ * and initialized blocks.
* We need exclusive i_rwsem for changing security info
* in file_modified().
*/
if (*ilock_shared && (!IS_NOSEC(inode) || *extend ||
- !ext4_should_dioread_nolock(inode) ||
!ext4_overwrite_io(inode, offset, count))) {
inode_unlock_shared(inode);
*ilock_shared = false;
--
2.21.0
