Commit e3e8e176 authored by Chuck Lever's avatar Chuck Lever
Browse files

NFSD: Make FILE_SYNC WRITEs comply with spec 



Mike noted that when NFSD responds to an NFS_FILE_SYNC WRITE, it
does not also persist file time stamps. To wit, Section 18.32.3
of RFC 8881 mandates:

> The client specifies with the stable parameter the method of how
> the data is to be processed by the server. If stable is
> FILE_SYNC4, the server MUST commit the data written plus all file
> system metadata to stable storage before returning results. This
> corresponds to the NFSv2 protocol semantics. Any other behavior
> constitutes a protocol violation. If stable is DATA_SYNC4, then
> the server MUST commit all of the data to stable storage and
> enough of the metadata to retrieve the data before returning.

Commit 3f3503ad ("NFSD: Use vfs_iocb_iter_write()") replaced:

-		flags |= RWF_SYNC;

with:

+		kiocb.ki_flags |= IOCB_DSYNC;

which appears to be correct given:

	if (flags & RWF_SYNC)
		kiocb_flags |= IOCB_DSYNC;

in kiocb_set_rw_flags(). However the author of that commit did not
appreciate that the previous line in kiocb_set_rw_flags() results
in IOCB_SYNC also being set:

	kiocb_flags |= (__force int) (flags & RWF_SUPPORTED);

RWF_SUPPORTED contains RWF_SYNC, and RWF_SYNC is the same bit as
IOCB_SYNC. Reviewers at the time did not catch the omission.

Reported-by: default avatarMike Snitzer <snitzer@kernel.org>
Closes: https://lore.kernel.org/linux-nfs/20251018005431.3403-1-cel@kernel.org/T/#t


Fixes: 3f3503ad ("NFSD: Use vfs_iocb_iter_write()")
Cc: stable@vger.kernel.org
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Reviewed-by: default avatarNeilBrown <neil@brown.name>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent 99f5aa14

fs/nfsd/vfs.c

+12 −2
Original line number Diff line number Diff line
@@ -1314,8 +1314,18 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, 
		stable = NFS_UNSTABLE;

	init_sync_kiocb(&kiocb, file);

	kiocb.ki_pos = offset;

	if (stable && !fhp->fh_use_wgather)

	if (likely(!fhp->fh_use_wgather)) {

		switch (stable) {

		case NFS_FILE_SYNC:

			/* persist data and timestamps */

			kiocb.ki_flags |= IOCB_DSYNC | IOCB_SYNC;

			break;

		case NFS_DATA_SYNC:

			/* persist data only */

			kiocb.ki_flags |= IOCB_DSYNC;

			break;

		}

	}



	nvecs = xdr_buf_to_bvec(rqstp->rq_bvec, rqstp->rq_maxpages, payload);

	iov_iter_bvec(&iter, ITER_SOURCE, rqstp->rq_bvec, nvecs, *cnt);