From bc6385dab125d20870f0eb9ca9e589f43abb3f56 Mon Sep 17 00:00:00 2001 From: Ritesh Harjani Date: Thu, 12 Dec 2019 11:25:57 +0530 Subject: ext4: Move to shared i_rwsem even without dioread_nolock mount opt 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 Tested-by: Joseph Qi Signed-off-by: Ritesh Harjani Link: https://lore.kernel.org/r/20191212055557.11151-4-riteshh@linux.ibm.com Signed-off-by: Theodore Ts'o --- fs/ext4/file.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) (limited to 'fs/ext4') 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 @@ restart: *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; -- cgit v1.2.3-59-g8ed1b