Re: [PATCH 5.10.x] btrfs: fix crash after non-aligned direct IO write with O_DSYNC

[Wang Yugui <wangyugui@e16-tech.com>]

Hi,

> This bug only affects 5.10 kernels, and the regression was introduced in
> 5.10-rc1 by commit 0eb79294dbe328 ("btrfs: dio iomap DSYNC workaround").
> The bug does not exist in 5.11 kernels due to commit ecfdc08b8cc65d
> ("btrfs: remove dio iomap DSYNC workaround"), which depends on other
> changes that went into the merge window for 5.11. So this is a fix only
> for 5.10.x stable kernels, as there are people hitting this.

It is OK too to backport commit ecfdc08b8cc65d
 ("btrfs: remove dio iomap DSYNC workaround") to 5.10 for this problem?

the iomap issue for commit 0eb79294dbe328 ("btrfs: dio iomap DSYNC workaround")
is already fixed in 5.10?

Best Regards
Wang Yugui (wangyugui@e16-tech.com)
2021/02/13


> Fixes: 0eb79294dbe328 ("btrfs: dio iomap DSYNC workaround")
> CC: stable@vger.kernel.org # 5.10 (and only 5.10)
> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1181605
> Signed-off-by: Filipe Manana <fdmanana@suse.com>
> ---
>  fs/btrfs/inode.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index acc47e2ffb46..b536d21541a9 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -8026,8 +8026,12 @@ ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>  	bool relock = false;
>  	ssize_t ret;
>  
> -	if (check_direct_IO(fs_info, iter, offset))
> +	if (check_direct_IO(fs_info, iter, offset)) {
> +		ASSERT(current->journal_info == NULL ||
> +		       current->journal_info == BTRFS_DIO_SYNC_STUB);
> +		current->journal_info = NULL;
>  		return 0;
> +	}
>  
>  	count = iov_iter_count(iter);
>  	if (iov_iter_rw(iter) == WRITE) {
> -- 
> 2.28.0