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authorChuck Lever <chuck.lever@oracle.com>2021-12-28 20:35:43 +0300
committerChuck Lever <chuck.lever@oracle.com>2022-01-08 22:42:02 +0300
commitf11ad7aa653130b71e2e89bed207f387718216d5 (patch)
tree15598cbae9f25e49ddea6d645d1e9daece9d95f9 /fs/nfsd/vfs.c
parent12bcbd40fd931472c7fc9cf3bfe66799ece93ed8 (diff)
downloadlinux-f11ad7aa653130b71e2e89bed207f387718216d5.tar.xz
NFSD: Fix verifier returned in stable WRITEs
RFC 8881 explains the purpose of the write verifier this way: > The final portion of the result is the field writeverf. This field > is the write verifier and is a cookie that the client can use to > determine whether a server has changed instance state (e.g., server > restart) between a call to WRITE and a subsequent call to either > WRITE or COMMIT. But then it says: > This cookie MUST be unchanged during a single instance of the > NFSv4.1 server and MUST be unique between instances of the NFSv4.1 > server. If the cookie changes, then the client MUST assume that > any data written with an UNSTABLE4 value for committed and an old > writeverf in the reply has been lost and will need to be > recovered. RFC 1813 has similar language for NFSv3. NFSv2 does not have a write verifier since it doesn't implement the COMMIT procedure. Since commit 19e0663ff9bc ("nfsd: Ensure sampling of the write verifier is atomic with the write"), the Linux NFS server has returned a boot-time-based verifier for UNSTABLE WRITEs, but a zero verifier for FILE_SYNC and DATA_SYNC WRITEs. FILE_SYNC and DATA_SYNC WRITEs are not followed up with a COMMIT, so there's no need for clients to compare verifiers for stable writes. However, by returning a different verifier for stable and unstable writes, the above commit puts the Linux NFS server a step farther out of compliance with the first MUST above. At least one NFS client (FreeBSD) noticed the difference, making this a potential regression. Reported-by: Rick Macklem <rmacklem@uoguelph.ca> Link: https://lore.kernel.org/linux-nfs/YQXPR0101MB096857EEACF04A6DF1FC6D9BDD749@YQXPR0101MB0968.CANPRD01.PROD.OUTLOOK.COM/T/ Fixes: 19e0663ff9bc ("nfsd: Ensure sampling of the write verifier is atomic with the write") Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Diffstat (limited to 'fs/nfsd/vfs.c')
-rw-r--r--fs/nfsd/vfs.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 0faa3839ea6c..74c3451c2089 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -995,6 +995,10 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
iov_iter_kvec(&iter, WRITE, vec, vlen, *cnt);
if (flags & RWF_SYNC) {
down_write(&nf->nf_rwsem);
+ if (verf)
+ nfsd_copy_boot_verifier(verf,
+ net_generic(SVC_NET(rqstp),
+ nfsd_net_id));
host_err = vfs_iter_write(file, &iter, &pos, flags);
if (host_err < 0)
nfsd_reset_boot_verifier(net_generic(SVC_NET(rqstp),