[PATCH] xfs: fix error code in xfs_iflush_cluster()

[PATCH] xfs: fix error code in xfs_iflush_cluster()

[Dan Carpenter]

Originally this function used to always return -EFSCORRUPTED on error
but now we're trying to return more informative error codes.
Unfortunately, there was one error path missed.  If this kmem_alloc()
allocation fails then we need to return -ENOMEM instead of success.

Fixes: f20192991d79 ("xfs: simplify inode flush error handling")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 fs/xfs/xfs_inode.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index ab31a5dec7aab..63aeda7cbafb0 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -3505,8 +3505,10 @@ xfs_iflush_cluster(
 
 	cilist_size = igeo->inodes_per_cluster * sizeof(struct xfs_inode *);
 	cilist = kmem_alloc(cilist_size, KM_MAYFAIL|KM_NOFS);
-	if (!cilist)
+	if (!cilist) {
+		error = -ENOMEM;
 		goto out_put;
+	}
 
 	mask = ~(igeo->inodes_per_cluster - 1);
 	first_index = XFS_INO_TO_AGINO(mp, ip->i_ino) & mask;
-- 
2.26.2

[PATCH] xfs: fix error code in xfs_iflush_cluster()

[Dan Carpenter]

Originally this function used to always return -EFSCORRUPTED on error
but now we're trying to return more informative error codes.
Unfortunately, there was one error path missed.  If this kmem_alloc()
allocation fails then we need to return -ENOMEM instead of success.

Fixes: f20192991d79 ("xfs: simplify inode flush error handling")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 fs/xfs/xfs_inode.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index ab31a5dec7aab..63aeda7cbafb0 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -3505,8 +3505,10 @@ xfs_iflush_cluster(
 
 	cilist_size = igeo->inodes_per_cluster * sizeof(struct xfs_inode *);
 	cilist = kmem_alloc(cilist_size, KM_MAYFAIL|KM_NOFS);
-	if (!cilist)
+	if (!cilist) {
+		error = -ENOMEM;
 		goto out_put;
+	}
 
 	mask = ~(igeo->inodes_per_cluster - 1);
 	first_index = XFS_INO_TO_AGINO(mp, ip->i_ino) & mask;
-- 
2.26.2

Re: [PATCH] xfs: fix error code in xfs_iflush_cluster()

[Brian Foster]

On Wed, May 13, 2020 at 12:48:03PM +0300, Dan Carpenter wrote:
> Originally this function used to always return -EFSCORRUPTED on error
> but now we're trying to return more informative error codes.
> Unfortunately, there was one error path missed.  If this kmem_alloc()
> allocation fails then we need to return -ENOMEM instead of success.
> 
> Fixes: f20192991d79 ("xfs: simplify inode flush error handling")

This logic predates that patch, and I think it may be by design. Inode
cluster flushing is an optimization to flush other dirty inodes in the
same cluster we're about to queue for writeback. If the cluster flush
fails due to an operational error such as memory allocation failure, we
don't want to report an error because that would shutdown the fs when
otherwise the side effect would be that the other inodes in the cluster
would be flushed individually. This is distinct from failing to flush a
particular inode due to corruption, which is a fatal filesystem error.

Brian

> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
>  fs/xfs/xfs_inode.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index ab31a5dec7aab..63aeda7cbafb0 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -3505,8 +3505,10 @@ xfs_iflush_cluster(
>  
>  	cilist_size = igeo->inodes_per_cluster * sizeof(struct xfs_inode *);
>  	cilist = kmem_alloc(cilist_size, KM_MAYFAIL|KM_NOFS);
> -	if (!cilist)
> +	if (!cilist) {
> +		error = -ENOMEM;
>  		goto out_put;
> +	}
>  
>  	mask = ~(igeo->inodes_per_cluster - 1);
>  	first_index = XFS_INO_TO_AGINO(mp, ip->i_ino) & mask;
> -- 
> 2.26.2
> 

Re: [PATCH] xfs: fix error code in xfs_iflush_cluster()

[Brian Foster]

On Wed, May 13, 2020 at 12:48:03PM +0300, Dan Carpenter wrote:
> Originally this function used to always return -EFSCORRUPTED on error
> but now we're trying to return more informative error codes.
> Unfortunately, there was one error path missed.  If this kmem_alloc()
> allocation fails then we need to return -ENOMEM instead of success.
> 
> Fixes: f20192991d79 ("xfs: simplify inode flush error handling")

This logic predates that patch, and I think it may be by design. Inode
cluster flushing is an optimization to flush other dirty inodes in the
same cluster we're about to queue for writeback. If the cluster flush
fails due to an operational error such as memory allocation failure, we
don't want to report an error because that would shutdown the fs when
otherwise the side effect would be that the other inodes in the cluster
would be flushed individually. This is distinct from failing to flush a
particular inode due to corruption, which is a fatal filesystem error.

Brian

> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
>  fs/xfs/xfs_inode.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index ab31a5dec7aab..63aeda7cbafb0 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -3505,8 +3505,10 @@ xfs_iflush_cluster(
>  
>  	cilist_size = igeo->inodes_per_cluster * sizeof(struct xfs_inode *);
>  	cilist = kmem_alloc(cilist_size, KM_MAYFAIL|KM_NOFS);
> -	if (!cilist)
> +	if (!cilist) {
> +		error = -ENOMEM;
>  		goto out_put;
> +	}
>  
>  	mask = ~(igeo->inodes_per_cluster - 1);
>  	first_index = XFS_INO_TO_AGINO(mp, ip->i_ino) & mask;
> -- 
> 2.26.2
> 

Re: [PATCH] xfs: fix error code in xfs_iflush_cluster()

[Dan Carpenter]

Oh yeah.  You're right.  This patch isn't correct.  Sorry about that.

I worry that there are several static analyzer's which will warn about
this code...

regards,
dan carpenter

Re: [PATCH] xfs: fix error code in xfs_iflush_cluster()

[Dan Carpenter]

Oh yeah.  You're right.  This patch isn't correct.  Sorry about that.

I worry that there are several static analyzer's which will warn about
this code...

regards,
dan carpenter

Re: [PATCH] xfs: fix error code in xfs_iflush_cluster()

[Darrick J. Wong]

On Wed, May 13, 2020 at 04:39:05PM +0300, Dan Carpenter wrote:
> Oh yeah.  You're right.  This patch isn't correct.  Sorry about that.
> 
> I worry that there are several static analyzer's which will warn about
> this code...

/me wonders if this particular instance ought to have a breadcrumb to
remind future readers that we can handle the lack of memory, e.g.

cilist = kmem_alloc(..., KM_MAYFAIL...);
if (!cilist) {
	/* memory is tight, so defer the inode cluster flush */
	goto out_put;
}

--D

> regards,
> dan carpenter
> 

Re: [PATCH] xfs: fix error code in xfs_iflush_cluster()

[Darrick J. Wong]

On Wed, May 13, 2020 at 04:39:05PM +0300, Dan Carpenter wrote:
> Oh yeah.  You're right.  This patch isn't correct.  Sorry about that.
> 
> I worry that there are several static analyzer's which will warn about
> this code...

/me wonders if this particular instance ought to have a breadcrumb to
remind future readers that we can handle the lack of memory, e.g.

cilist = kmem_alloc(..., KM_MAYFAIL...);
if (!cilist) {
	/* memory is tight, so defer the inode cluster flush */
	goto out_put;
}

--D

> regards,
> dan carpenter
> 

Re: [PATCH] xfs: fix error code in xfs_iflush_cluster()

[Dave Chinner]

On Wed, May 13, 2020 at 08:17:54AM -0700, Darrick J. Wong wrote:
> On Wed, May 13, 2020 at 04:39:05PM +0300, Dan Carpenter wrote:
> > Oh yeah.  You're right.  This patch isn't correct.  Sorry about that.
> > 
> > I worry that there are several static analyzer's which will warn about
> > this code...
> 
> /me wonders if this particular instance ought to have a breadcrumb to
> remind future readers that we can handle the lack of memory, e.g.
> 
> cilist = kmem_alloc(..., KM_MAYFAIL...);
> if (!cilist) {
> 	/* memory is tight, so defer the inode cluster flush */
> 	goto out_put;
> }

I'm working on patches that make this memory allocation go away
altogether, so I'd suggest just ignoring it for now.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

Re: [PATCH] xfs: fix error code in xfs_iflush_cluster()

[Dave Chinner]

On Wed, May 13, 2020 at 08:17:54AM -0700, Darrick J. Wong wrote:
> On Wed, May 13, 2020 at 04:39:05PM +0300, Dan Carpenter wrote:
> > Oh yeah.  You're right.  This patch isn't correct.  Sorry about that.
> > 
> > I worry that there are several static analyzer's which will warn about
> > this code...
> 
> /me wonders if this particular instance ought to have a breadcrumb to
> remind future readers that we can handle the lack of memory, e.g.
> 
> cilist = kmem_alloc(..., KM_MAYFAIL...);
> if (!cilist) {
> 	/* memory is tight, so defer the inode cluster flush */
> 	goto out_put;
> }

I'm working on patches that make this memory allocation go away
altogether, so I'd suggest just ignoring it for now.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com