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| author | Jeff Layton <jlayton@poochiereds.net> | 2015-10-01 15:05:50 +0200 |
|---|---|---|
| committer | J. Bruce Fields <bfields@redhat.com> | 2015-10-23 21:57:33 +0200 |
| commit | 9767feb2c64b29775f1ea683130b44f95f67d169 (patch) | |
| tree | cfde0f75348706306314749a9ac8164d0237a0d4 /fs/nfsd/nfs4layouts.c | |
| parent | nfsd: serialize layout stateid morphing operations (diff) | |
| download | linux-9767feb2c64b29775f1ea683130b44f95f67d169.tar.xz linux-9767feb2c64b29775f1ea683130b44f95f67d169.zip | |
nfsd: ensure that seqid morphing operations are atomic wrt to copies
Bruce points out that the increment of the seqid in stateids is not
serialized in any way, so it's possible for racing calls to bump it
twice and end up sending the same stateid. While we don't have any
reports of this problem it _is_ theoretically possible, and could lead
to spurious state recovery by the client.
In the current code, update_stateid is always followed by a memcpy of
that stateid, so we can combine the two operations. For better
atomicity, we add a spinlock to the nfs4_stid and hold that when bumping
the seqid and copying the stateid.
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Diffstat (limited to 'fs/nfsd/nfs4layouts.c')
| -rw-r--r-- | fs/nfsd/nfs4layouts.c | 13 |
1 files changed, 4 insertions, 9 deletions
diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c index 4a68ab901b4b..9ffef06b30d5 100644 --- a/fs/nfsd/nfs4layouts.c +++ b/fs/nfsd/nfs4layouts.c @@ -409,8 +409,7 @@ nfsd4_insert_layout(struct nfsd4_layoutget *lgp, struct nfs4_layout_stateid *ls) list_add_tail(&new->lo_perstate, &ls->ls_layouts); new = NULL; done: - update_stateid(&ls->ls_stid.sc_stateid); - memcpy(&lgp->lg_sid, &ls->ls_stid.sc_stateid, sizeof(stateid_t)); + nfs4_inc_and_copy_stateid(&lgp->lg_sid, &ls->ls_stid); spin_unlock(&ls->ls_lock); out: spin_unlock(&fp->fi_lock); @@ -484,11 +483,8 @@ nfsd4_return_file_layouts(struct svc_rqst *rqstp, } } if (!list_empty(&ls->ls_layouts)) { - if (found) { - update_stateid(&ls->ls_stid.sc_stateid); - memcpy(&lrp->lr_sid, &ls->ls_stid.sc_stateid, - sizeof(stateid_t)); - } + if (found) + nfs4_inc_and_copy_stateid(&lrp->lr_sid, &ls->ls_stid); lrp->lrs_present = 1; } else { trace_layoutstate_unhash(&ls->ls_stid.sc_stateid); @@ -619,8 +615,7 @@ nfsd4_cb_layout_prepare(struct nfsd4_callback *cb) container_of(cb, struct nfs4_layout_stateid, ls_recall); mutex_lock(&ls->ls_mutex); - update_stateid(&ls->ls_stid.sc_stateid); - memcpy(&ls->ls_recall_sid, &ls->ls_stid.sc_stateid, sizeof(stateid_t)); + nfs4_inc_and_copy_stateid(&ls->ls_recall_sid, &ls->ls_stid); } static int |