[PATCH 2/4] xfs: return errors from partial I/O failures to files

[PATCH 2/4] xfs: return errors from partial I/O failures to files

[billodo]

From: David Jeffery <djeffery@redhat.com>

There is an issue with xfs's error reporting in some cases of I/O partially
failing and partially succeeding. Calls like fsync() can report success even
though not all I/O was successful in partial-failure cases such as one disk of
a RAID0 array being offline.

The issue can occur when there are more than one bio per xfs_ioend struct.
Each call to xfs_end_bio() for a bio completing will write a value to
ioend->io_error.  If a successful bio completes after any failed bio, no
error is reported do to it writing 0 over the error code set by any failed bio.
The I/O error information is now lost and when the ioend is completed
only success is reported back up the filesystem stack.

xfs_end_bio() should only set ioend->io_error in the case of BIO_UPTODATE
being clear.  ioend->io_error is initialized to 0 at allocation so only needs
to be updated by a failed bio. Also check that ioend->io_error is 0 so that
the first error reported will be the error code returned.

Cc: stable@vger.kernel.org
Signed-off-by: David Jeffery <djeffery@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: billodo <billodo@redhat.com>
---
 fs/xfs/xfs_aops.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 3859f5e..458fced 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -356,7 +356,8 @@ xfs_end_bio(
 {
 	xfs_ioend_t		*ioend = bio->bi_private;
 
-	ioend->io_error = test_bit(BIO_UPTODATE, &bio->bi_flags) ? 0 : error;
+	if (!ioend->io_error && !test_bit(BIO_UPTODATE, &bio->bi_flags))
+		ioend->io_error = error;
 
 	/* Toss bio and pass work off to an xfsdatad thread */
 	bio->bi_private = NULL;
-- 
2.4.3

Re: [PATCH 2/4] xfs: return errors from partial I/O failures to files

[Bill O'Donnell]

please disregard. Mistake with guilt. :(


On Thu, Sep 03, 2015 at 10:26:24AM -0500, billodo wrote:
> From: David Jeffery <djeffery@redhat.com>
> 
> There is an issue with xfs's error reporting in some cases of I/O partially
> failing and partially succeeding. Calls like fsync() can report success even
> though not all I/O was successful in partial-failure cases such as one disk of
> a RAID0 array being offline.
> 
> The issue can occur when there are more than one bio per xfs_ioend struct.
> Each call to xfs_end_bio() for a bio completing will write a value to
> ioend->io_error.  If a successful bio completes after any failed bio, no
> error is reported do to it writing 0 over the error code set by any failed bio.
> The I/O error information is now lost and when the ioend is completed
> only success is reported back up the filesystem stack.
> 
> xfs_end_bio() should only set ioend->io_error in the case of BIO_UPTODATE
> being clear.  ioend->io_error is initialized to 0 at allocation so only needs
> to be updated by a failed bio. Also check that ioend->io_error is 0 so that
> the first error reported will be the error code returned.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: David Jeffery <djeffery@redhat.com>
> Reviewed-by: Dave Chinner <dchinner@redhat.com>
> Signed-off-by: Dave Chinner <david@fromorbit.com>
> Signed-off-by: billodo <billodo@redhat.com>
> ---
>  fs/xfs/xfs_aops.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 3859f5e..458fced 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -356,7 +356,8 @@ xfs_end_bio(
>  {
>  	xfs_ioend_t		*ioend = bio->bi_private;
>  
> -	ioend->io_error = test_bit(BIO_UPTODATE, &bio->bi_flags) ? 0 : error;
> +	if (!ioend->io_error && !test_bit(BIO_UPTODATE, &bio->bi_flags))
> +		ioend->io_error = error;
>  
>  	/* Toss bio and pass work off to an xfsdatad thread */
>  	bio->bi_private = NULL;
> -- 
> 2.4.3
>