[1/2] NFS: Add FATTR4_WORD1_SPACE_USED to the cache_consistency_bitmask
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Message ID 20191108210224.33645-1-Anna.Schumaker@Netapp.com
State New
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  • [1/2] NFS: Add FATTR4_WORD1_SPACE_USED to the cache_consistency_bitmask
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Commit Message

Anna Schumaker Nov. 8, 2019, 9:02 p.m. UTC
From: Anna Schumaker <Anna.Schumaker@Netapp.com>

Changing a sparse file could have an effect not only on the file size,
but also on the number of blocks used by the file in the underlying
filesystem. Let's update the SPACE_USED attribute whenever we update
SIZE to be as accurate as possible.

This patch fixes xfstests generic/568, which tests that fallocating an
unaligned range allocates all blocks touched by that range. Without this
patch, `stat` reports 0 bytes used immediately after the fallocate.
Adding a `sleep 5` to the test also catches the update, but it's better
to just do it when we know something has changed.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
 fs/nfs/nfs4proc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Trond Myklebust Nov. 8, 2019, 9:22 p.m. UTC | #1
On Fri, 2019-11-08 at 16:02 -0500, schumaker.anna@gmail.com wrote:
> From: Anna Schumaker <Anna.Schumaker@Netapp.com>
> 
> Changing a sparse file could have an effect not only on the file
> size,
> but also on the number of blocks used by the file in the underlying
> filesystem. Let's update the SPACE_USED attribute whenever we update
> SIZE to be as accurate as possible.
> 
> This patch fixes xfstests generic/568, which tests that fallocating
> an
> unaligned range allocates all blocks touched by that range. Without
> this
> patch, `stat` reports 0 bytes used immediately after the fallocate.
> Adding a `sleep 5` to the test also catches the update, but it's
> better
> to just do it when we know something has changed.
> 
> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
> ---
>  fs/nfs/nfs4proc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index ac9063c06205..00a1f3ec7f22 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -3775,7 +3775,7 @@ static int _nfs4_server_capabilities(struct
> nfs_server *server, struct nfs_fh *f
>  
>  		memcpy(server->cache_consistency_bitmask,
> res.attr_bitmask, sizeof(server->cache_consistency_bitmask));
>  		server->cache_consistency_bitmask[0] &=
> FATTR4_WORD0_CHANGE|FATTR4_WORD0_SIZE;
> -		server->cache_consistency_bitmask[1] &=
> FATTR4_WORD1_TIME_METADATA|FATTR4_WORD1_TIME_MODIFY;
> +		server->cache_consistency_bitmask[1] &=
> FATTR4_WORD1_TIME_METADATA|FATTR4_WORD1_TIME_MODIFY|FATTR4_WORD1_SPAC
> E_USED;

I'd rather not do this. Space used is not a cache consistency attribute
, as we do not use it to revalidate the cache and it can be rather
expensive to retrieve on some platforms.

I'd therefore prefer that we just make sure we mark the cache validity
with NFS_INO_INVALID_OTHER when we have a write succeed on a sparse
file.

>  		server->cache_consistency_bitmask[2] = 0;
>  
>  		/* Avoid a regression due to buggy server */
Anna Schumaker Nov. 11, 2019, 4:24 p.m. UTC | #2
Hi Trond,

On Fri, 2019-11-08 at 21:22 +0000, Trond Myklebust wrote:
> On Fri, 2019-11-08 at 16:02 -0500, schumaker.anna@gmail.com wrote:
> > From: Anna Schumaker <Anna.Schumaker@Netapp.com>
> > 
> > Changing a sparse file could have an effect not only on the file
> > size,
> > but also on the number of blocks used by the file in the underlying
> > filesystem. Let's update the SPACE_USED attribute whenever we update
> > SIZE to be as accurate as possible.
> > 
> > This patch fixes xfstests generic/568, which tests that fallocating
> > an
> > unaligned range allocates all blocks touched by that range. Without
> > this
> > patch, `stat` reports 0 bytes used immediately after the fallocate.
> > Adding a `sleep 5` to the test also catches the update, but it's
> > better
> > to just do it when we know something has changed.
> > 
> > Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
> > ---
> >  fs/nfs/nfs4proc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> > index ac9063c06205..00a1f3ec7f22 100644
> > --- a/fs/nfs/nfs4proc.c
> > +++ b/fs/nfs/nfs4proc.c
> > @@ -3775,7 +3775,7 @@ static int _nfs4_server_capabilities(struct
> > nfs_server *server, struct nfs_fh *f
> >  
> >  		memcpy(server->cache_consistency_bitmask,
> > res.attr_bitmask, sizeof(server->cache_consistency_bitmask));
> >  		server->cache_consistency_bitmask[0] &=
> > FATTR4_WORD0_CHANGE|FATTR4_WORD0_SIZE;
> > -		server->cache_consistency_bitmask[1] &=
> > FATTR4_WORD1_TIME_METADATA|FATTR4_WORD1_TIME_MODIFY;
> > +		server->cache_consistency_bitmask[1] &=
> > FATTR4_WORD1_TIME_METADATA|FATTR4_WORD1_TIME_MODIFY|FATTR4_WORD1_SPAC
> > E_USED;
> 
> I'd rather not do this. Space used is not a cache consistency attribute
> , as we do not use it to revalidate the cache and it can be rather
> expensive to retrieve on some platforms.

Okay, that makes sense.

> 
> I'd therefore prefer that we just make sure we mark the cache validity
> with NFS_INO_INVALID_OTHER when we have a write succeed on a sparse
> file.

It looks like setting falloc_bitmask to use the standard nfs4_fattr_bitmap
instead of the cache_consistency_bitmask will also update the SPACE_USED
attribute after a fallocate call.

I'll play around with NFS_INO_INVALID_OTHER next, but making use of the trailing
getattr that ALLOCATE and DEALLOCATE already have seems more straightforward to
me.

Anna

> 
> >  		server->cache_consistency_bitmask[2] = 0;
> >  
> >  		/* Avoid a regression due to buggy server */
> -- 
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@hammerspace.com
> 
>

Patch
diff mbox series

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index ac9063c06205..00a1f3ec7f22 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3775,7 +3775,7 @@  static int _nfs4_server_capabilities(struct nfs_server *server, struct nfs_fh *f
 
 		memcpy(server->cache_consistency_bitmask, res.attr_bitmask, sizeof(server->cache_consistency_bitmask));
 		server->cache_consistency_bitmask[0] &= FATTR4_WORD0_CHANGE|FATTR4_WORD0_SIZE;
-		server->cache_consistency_bitmask[1] &= FATTR4_WORD1_TIME_METADATA|FATTR4_WORD1_TIME_MODIFY;
+		server->cache_consistency_bitmask[1] &= FATTR4_WORD1_TIME_METADATA|FATTR4_WORD1_TIME_MODIFY|FATTR4_WORD1_SPACE_USED;
 		server->cache_consistency_bitmask[2] = 0;
 
 		/* Avoid a regression due to buggy server */