On Fri, Aug 01, 2025 at 04:52:38PM -0400, Chuck Lever wrote:
> On 7/31/25 7:06 PM, Mike Snitzer wrote:
> > Refactor nfsd_vfs_write() to support splitting a WRITE into parts
> > (which will be either misaligned or DIO-aligned). Doing so in a
> > preliminary commit just allows for indentation and slight
> > transformation to be more easily understood and reviewed.
> >
> > Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> > Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
> > ---
> > fs/nfsd/vfs.c | 45 +++++++++++++++++++++++++++------------------
> > 1 file changed, 27 insertions(+), 18 deletions(-)
> >
> > diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> > index 35c29b8ade9c3..edac73349da0f 100644
> > --- a/fs/nfsd/vfs.c
> > +++ b/fs/nfsd/vfs.c
> > @@ -1341,7 +1341,6 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > struct super_block *sb = file_inode(file)->i_sb;
> > struct kiocb kiocb;
> > struct svc_export *exp;
> > - struct iov_iter iter;
> > errseq_t since;
> > __be32 nfserr;
> > int host_err;
> > @@ -1349,6 +1348,9 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > unsigned int pflags = current->flags;
> > bool restore_flags = false;
> > unsigned int nvecs;
> > + struct iov_iter iter_stack[1];
> > + struct iov_iter *iter = iter_stack;
> > + unsigned int n_iters = 0;
> >
> > trace_nfsd_write_opened(rqstp, fhp, offset, *cnt);
> >
> > @@ -1378,14 +1380,15 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > kiocb.ki_flags |= IOCB_DSYNC;
> >
> > nvecs = xdr_buf_to_bvec(rqstp->rq_bvec, rqstp->rq_maxpages, payload);
> > - iov_iter_bvec(&iter, ITER_SOURCE, rqstp->rq_bvec, nvecs, *cnt);
> > + iov_iter_bvec(&iter[0], ITER_SOURCE, rqstp->rq_bvec, nvecs, *cnt);
> > + n_iters++;
> >
> > switch (nfsd_io_cache_write) {
> > case NFSD_IO_DIRECT:
> > /* direct I/O must be aligned to device logical sector size */
> > if (nf->nf_dio_mem_align && nf->nf_dio_offset_align &&
> > (((offset | *cnt) & (nf->nf_dio_offset_align-1)) == 0) &&
> > - iov_iter_is_aligned(&iter, nf->nf_dio_mem_align - 1,
> > + iov_iter_is_aligned(&iter[0], nf->nf_dio_mem_align - 1,
> > nf->nf_dio_offset_align - 1))
> > kiocb.ki_flags = IOCB_DIRECT;
> > break;
> > @@ -1399,22 +1402,28 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
> > since = READ_ONCE(file->f_wb_err);
> > if (verf)
> > nfsd_copy_write_verifier(verf, nn);
> > - host_err = vfs_iocb_iter_write(file, &kiocb, &iter);
> > - if (host_err < 0) {
> > - commit_reset_write_verifier(nn, rqstp, host_err);
> > - goto out_nfserr;
> > - }
> > - *cnt = host_err;
> > - nfsd_stats_io_write_add(nn, exp, *cnt);
> > - fsnotify_modify(file);
> > - host_err = filemap_check_wb_err(file->f_mapping, since);
> > - if (host_err < 0)
> > - goto out_nfserr;
> > -
> > - if (stable && fhp->fh_use_wgather) {
> > - host_err = wait_for_concurrent_writes(file);
> > - if (host_err < 0)
> > + *cnt = 0;
> > + for (int i = 0; i < n_iters; i++) {
> > + host_err = vfs_iocb_iter_write(file, &kiocb, &iter[i]);
> > + if (host_err < 0) {
> > commit_reset_write_verifier(nn, rqstp, host_err);
> > + goto out_nfserr;
> > + }
>
> Does this loop wait after each iter is written? Would it be better to
> wait once after all the iters have been written?
It does, sorry about that. This incremental fixes it up and is easily
folded into this patch:
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 2eabcb5651ba..1590fc1fb420 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1533,19 +1533,17 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp,
}
*cnt += host_err;
nfsd_stats_io_write_add(nn, exp, host_err);
+ }
- fsnotify_modify(file);
- host_err = filemap_check_wb_err(file->f_mapping, since);
+ fsnotify_modify(file);
+ host_err = filemap_check_wb_err(file->f_mapping, since);
+ if (host_err < 0)
+ goto out_nfserr;
+
+ if (stable && fhp->fh_use_wgather) {
+ host_err = wait_for_concurrent_writes(file);
if (host_err < 0)
- goto out_nfserr;
-
- if (stable && fhp->fh_use_wgather) {
- host_err = wait_for_concurrent_writes(file);
- if (host_err < 0) {
- commit_reset_write_verifier(nn, rqstp, host_err);
- goto out_nfserr;
- }
- }
+ commit_reset_write_verifier(nn, rqstp, host_err);
}
out_nfserr:
