Commit 1ebf9801 authored by Trond Myklebust's avatar Trond Myklebust Committed by Anna Schumaker
Browse files

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: default avatarOlga Kornievskaia <kolga@netapp.com>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent ecbb903c
......@@ -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:
......
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