linux-kernel - [PATCH 5.8 025/148] ext4: do not block RWF

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Date:   Mon, 24 Aug 2020 10:28:43 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, stable@...nel.org,
        Filipe Manana <fdmanana@...il.com>, Jan Kara <jack@...e.cz>,
        Ritesh Harjani <riteshh@...ux.ibm.com>,
        Theodore Tso <tytso@....edu>
Subject: [PATCH 5.8 025/148] ext4: do not block RWF_NOWAIT dio write on unallocated space

From: Jan Kara <jack@...e.cz>

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@...nel.org
Reported-by: Filipe Manana <fdmanana@...il.com>
Signed-off-by: Jan Kara <jack@...e.cz>
Reviewed-by: Ritesh Harjani <riteshh@...ux.ibm.com>
Link: https://lore.kernel.org/r/20200708153516.9507-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/ext4/file.c |    4 ++++
 1 file changed, 4 insertions(+)

--- 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);