From: Jan Kara <jack@suse.cz>
Date: Wed, 8 Jul 2020 15:35:16 +0000 (+0200)
Subject: ext4: do not block RWF_NOWAIT dio write on unallocated space
X-Git-Tag: v5.7.18~111
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d971e09b1b6cb02322eab1ff9c58409a173f6e48;p=thirdparty%2Fkernel%2Fstable.git

ext4: do not block RWF_NOWAIT dio write on unallocated space

commit 0b3171b6d195637f84ddf8b59bae818ea20bc8ac upstream.

Since commit 378f32bab371 ("ext4: introduce direct I/O write using iomap
infrastructure") we don't properly bail out of RWF_NOWAIT direct IO
write if underlying blocks are not allocated. Also
ext4_dio_write_checks() does not honor RWF_NOWAIT when re-acquiring
i_rwsem. Fix both issues.

Fixes: 378f32bab371 ("ext4: introduce direct I/O write using iomap infrastructure")
Cc: stable@kernel.org
Reported-by: Filipe Manana <fdmanana@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/r/20200708153516.9507-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 2a01e31a032c4..8f742b53f1d40 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -428,6 +428,10 @@ restart:
 	 */
 	if (*ilock_shared && (!IS_NOSEC(inode) || *extend ||
 	     !ext4_overwrite_io(inode, offset, count))) {
+		if (iocb->ki_flags & IOCB_NOWAIT) {
+			ret = -EAGAIN;
+			goto out;
+		}
 		inode_unlock_shared(inode);
 		*ilock_shared = false;
 		inode_lock(inode);