ext4: do not block RWF_NOWAIT dio write on unallocated space

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>

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 453cafecf5cc0ff120a2485a3d1ab9f8229bfa6d..7a2720517bbb92554bf2599702eb13e1ee108f76 100644 (file)
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -427,6 +427,10 @@ 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);