Merge branch 'locking/urgent' into locking/core, to pick up locking fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index ed3c0d6546c5..0b568c8d24cb 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1090,7 +1090,7 @@ ssize_t btrfs_buffered_write(struct kiocb *iocb, struct iov_iter *i)
 	u64 lockend;
 	size_t num_written = 0;
 	ssize_t ret;
-	loff_t old_isize = i_size_read(inode);
+	loff_t old_isize;
 	unsigned int ilock_flags = 0;
 	const bool nowait = (iocb->ki_flags & IOCB_NOWAIT);
 	unsigned int bdp_flags = (nowait ? BDP_ASYNC : 0);
@@ -1103,6 +1103,13 @@ ssize_t btrfs_buffered_write(struct kiocb *iocb, struct iov_iter *i)
 	if (ret < 0)
 		return ret;
 
+	/*
+	 * We can only trust the isize with inode lock held, or it can race with
+	 * other buffered writes and cause incorrect call of
+	 * pagecache_isize_extended() to overwrite existing data.
+	 */
+	old_isize = i_size_read(inode);
+
 	ret = generic_write_checks(iocb, i);
 	if (ret <= 0)
 		goto out;