lkml.org 
[lkml]   [2022]   [Jan]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.16 0809/1039] NFSD: Fix verifier returned in stable WRITEs
    Date
    From: Chuck Lever <chuck.lever@oracle.com>

    [ Upstream commit f11ad7aa653130b71e2e89bed207f387718216d5 ]

    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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/nfsd/vfs.c | 4 ++++
    1 file changed, 4 insertions(+)

    diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
    index c99857689e2c2..7f2472e4b88f9 100644
    --- a/fs/nfsd/vfs.c
    +++ b/fs/nfsd/vfs.c
    @@ -987,6 +987,10 @@ 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),
    --
    2.34.1


    \
     
     \ /
      Last update: 2022-01-25 00:11    [W:2.651 / U:1.488 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site