This is a note to let you know that I've just added the patch titled
btrfs: fix failure of RWF_NOWAIT write into prealloc extent beyond eof
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
btrfs-fix-failure-of-rwf_nowait-write-into-prealloc-extent-beyond-eof.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4b1946284dd6641afdb9457101056d9e6ee6204c Mon Sep 17 00:00:00 2001
From: Filipe Manana <fdmanana@xxxxxxxx>
Date: Mon, 15 Jun 2020 18:48:58 +0100
Subject: btrfs: fix failure of RWF_NOWAIT write into prealloc extent beyond eof
From: Filipe Manana <fdmanana@xxxxxxxx>
commit 4b1946284dd6641afdb9457101056d9e6ee6204c upstream.
If we attempt to write to prealloc extent located after eof using a
RWF_NOWAIT write, we always fail with -EAGAIN.
We do actually check if we have an allocated extent for the write at
the start of btrfs_file_write_iter() through a call to check_can_nocow(),
but later when we go into the actual direct IO write path we simply
return -EAGAIN if the write starts at or beyond EOF.
Trivial to reproduce:
$ mkfs.btrfs -f /dev/sdb
$ mount /dev/sdb /mnt
$ touch /mnt/foo
$ chattr +C /mnt/foo
$ xfs_io -d -c "pwrite -S 0xab 0 64K" /mnt/foo
wrote 65536/65536 bytes at offset 0
64 KiB, 16 ops; 0.0004 sec (135.575 MiB/sec and 34707.1584 ops/sec)
$ xfs_io -c "falloc -k 64K 1M" /mnt/foo
$ xfs_io -d -c "pwrite -N -V 1 -S 0xfe -b 64K 64K 64K" /mnt/foo
pwrite: Resource temporarily unavailable
On xfs and ext4 the write succeeds, as expected.
Fix this by removing the wrong check at btrfs_direct_IO().
Fixes: edf064e7c6fec3 ("btrfs: nowait aio support")
CC: stable@xxxxxxxxxxxxxxx # 4.14+
Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/inode.c | 3 ---
1 file changed, 3 deletions(-)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8857,9 +8857,6 @@ static ssize_t btrfs_direct_IO(struct ki
dio_data.overwrite = 1;
inode_unlock(inode);
relock = true;
- } else if (iocb->ki_flags & IOCB_NOWAIT) {
- ret = -EAGAIN;
- goto out;
}
ret = btrfs_delalloc_reserve_space(inode, &data_reserved,
offset, count);
Patches currently in stable-queue which might be from fdmanana@xxxxxxxx are
queue-5.4/btrfs-fix-bytes_may_use-underflow-when-running-balance-and-scrub-in-parallel.patch
queue-5.4/btrfs-fix-failure-of-rwf_nowait-write-into-prealloc-extent-beyond-eof.patch
queue-5.4/btrfs-check-if-a-log-root-exists-before-locking-the-log_mutex-on-unlink.patch
queue-5.4/btrfs-fix-data-block-group-relocation-failure-due-to-concurrent-scrub.patch
queue-5.4/btrfs-fix-a-block-group-ref-counter-leak-after-failu.patch
