2014-10-06 23:43:03

by Zach Brown

Subject: [PATCH] nfsd: fix inclusive vfs_fsync_range() end

The vfs_fsync_range() call during write processing got the end of the
range off by one. The range is inclusive, not exclusive. The error has
nfsd sync more data than requested -- it's correct but unnecessary
overhead.

The call during commit processing is correct so I copied that pattern in
write processing. Maybe a helper would be nice but I kept it trivial.

This is untested. I found it while reviewing code for something else
entirely.

Signed-off-by: Zach Brown <[email protected]>
---
fs/nfsd/vfs.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index f501a9b..825250e 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -921,6 +921,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
int stable = *stablep;
int use_wgather;
loff_t pos = offset;
+ loff_t end = LLONG_MAX;
unsigned int pflags = current->flags;

if (rqstp->rq_local)
@@ -952,10 +953,13 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
fsnotify_modify(file);

if (stable) {
- if (use_wgather)
+ if (use_wgather) {
host_err = wait_for_concurrent_writes(file);
- else
- host_err = vfs_fsync_range(file, offset, offset+*cnt, 0);
+ } else {
+ if (*cnt)
+ end = offset + *cnt - 1;
+ host_err = vfs_fsync_range(file, offset, end, 0);
+ }
}

out_nfserr:
--
1.9.3

2014-10-07 12:32:25

by J. Bruce Fields

Subject: Re: [PATCH] nfsd: fix inclusive vfs_fsync_range() end

On Mon, Oct 06, 2014 at 04:42:52PM -0700, Zach Brown wrote:
> The vfs_fsync_range() call during write processing got the end of the
> range off by one. The range is inclusive, not exclusive. The error has
> nfsd sync more data than requested -- it's correct but unnecessary
> overhead.
>
> The call during commit processing is correct so I copied that pattern in
> write processing. Maybe a helper would be nice but I kept it trivial.
>
> This is untested. I found it while reviewing code for something else
> entirely.

Makes sense to me, thanks! Queuing up for 3.19.--b.

>
> Signed-off-by: Zach Brown <[email protected]>
> ---
> fs/nfsd/vfs.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index f501a9b..825250e 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -921,6 +921,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
> int stable = *stablep;
> int use_wgather;
> loff_t pos = offset;
> + loff_t end = LLONG_MAX;
> unsigned int pflags = current->flags;
>
> if (rqstp->rq_local)
> @@ -952,10 +953,13 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
> fsnotify_modify(file);
>
> if (stable) {
> - if (use_wgather)
> + if (use_wgather) {
> host_err = wait_for_concurrent_writes(file);
> - else
> - host_err = vfs_fsync_range(file, offset, offset+*cnt, 0);
> + } else {
> + if (*cnt)
> + end = offset + *cnt - 1;
> + host_err = vfs_fsync_range(file, offset, end, 0);
> + }
> }
>
> out_nfserr:
> --
> 1.9.3
>