file_remove_privs might call into notify_change(), which
requires to hold an exclusive lock.
Fixes: e9adabb9712e ("btrfs: use shared lock for direct writes within EOF")
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Cc: Dharmendra Singh <dsingh@xxxxxxx>
Cc: David Sterba <dsterba@xxxxxxxx>
Cc: linux-btrfs@xxxxxxxxxxxxxxx
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Bernd Schubert <bschubert@xxxxxxx>
---
fs/btrfs/file.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index fd03e689a6be..c4b304a2948e 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1466,8 +1466,12 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
if (iocb->ki_flags & IOCB_NOWAIT)
ilock_flags |= BTRFS_ILOCK_TRY;
- /* If the write DIO is within EOF, use a shared lock */
- if (iocb->ki_pos + iov_iter_count(from) <= i_size_read(inode))
+ /* If the write DIO is within EOF, use a shared lock and also only
+ * if security bits will likely not be dropped. Either will need
+ * to be rechecked after the lock was acquired.
+ */
+ if (iocb->ki_pos + iov_iter_count(from) <= i_size_read(inode) &&
+ IS_NOSEC(inode))
ilock_flags |= BTRFS_ILOCK_SHARED;
relock:
@@ -1475,6 +1479,12 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
if (err < 0)
return err;
+ if (ilock_flags & BTRFS_ILOCK_SHARED && !IS_NOSEC(inode)) {
+ btrfs_inode_unlock(BTRFS_I(inode), ilock_flags);
+ ilock_flags &= ~BTRFS_ILOCK_SHARED;
+ goto relock;
+ }
+
err = generic_write_checks(iocb, from);
if (err <= 0) {
btrfs_inode_unlock(BTRFS_I(inode), ilock_flags);
--
2.39.2
