diff options
| author | Trond Myklebust <trond.myklebust@primarydata.com> | 2017-07-20 17:00:02 -0400 |
|---|---|---|
| committer | Anna Schumaker <Anna.Schumaker@Netapp.com> | 2017-07-21 14:08:45 -0400 |
| commit | 1ebf980127924c639e2b85c08468311ba1c95b70 (patch) | |
| tree | 514331ff7257270cc81f6963cc483b91cd0f0530 | |
| parent | ecbb903c56745d59c301db26dd7d8b74b520eb84 (diff) | |
| download | lwn-1ebf980127924c639e2b85c08468311ba1c95b70.tar.gz lwn-1ebf980127924c639e2b85c08468311ba1c95b70.zip | |
NFS/filelayout: Fix racy setting of fl->dsaddr in filelayout_check_deviceid()
We must set fl->dsaddr once, and once only, even if there are multiple
processes calling filelayout_check_deviceid() for the same layout
segment.
Reported-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
| -rw-r--r-- | fs/nfs/filelayout/filelayout.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/fs/nfs/filelayout/filelayout.c b/fs/nfs/filelayout/filelayout.c index 080fc6b278bd..44c638b7876c 100644 --- a/fs/nfs/filelayout/filelayout.c +++ b/fs/nfs/filelayout/filelayout.c @@ -542,6 +542,10 @@ filelayout_check_deviceid(struct pnfs_layout_hdr *lo, struct nfs4_file_layout_dsaddr *dsaddr; int status = -EINVAL; + /* Is the deviceid already set? If so, we're good. */ + if (fl->dsaddr != NULL) + return 0; + /* find and reference the deviceid */ d = nfs4_find_get_deviceid(NFS_SERVER(lo->plh_inode), &fl->deviceid, lo->plh_lc_cred, gfp_flags); @@ -553,8 +557,6 @@ filelayout_check_deviceid(struct pnfs_layout_hdr *lo, if (filelayout_test_devid_unavailable(&dsaddr->id_node)) goto out_put; - fl->dsaddr = dsaddr; - if (fl->first_stripe_index >= dsaddr->stripe_count) { dprintk("%s Bad first_stripe_index %u\n", __func__, fl->first_stripe_index); @@ -570,6 +572,13 @@ filelayout_check_deviceid(struct pnfs_layout_hdr *lo, goto out_put; } status = 0; + + /* + * Atomic compare and xchange to ensure we don't scribble + * over a non-NULL pointer. + */ + if (cmpxchg(&fl->dsaddr, NULL, dsaddr) != NULL) + goto out_put; out: return status; out_put: |