forked from luck/tmp_suning_uos_patched
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>
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@ -542,6 +542,10 @@ filelayout_check_deviceid(struct pnfs_layout_hdr *lo,
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struct nfs4_file_layout_dsaddr *dsaddr;
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int status = -EINVAL;
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/* Is the deviceid already set? If so, we're good. */
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if (fl->dsaddr != NULL)
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return 0;
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/* find and reference the deviceid */
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d = nfs4_find_get_deviceid(NFS_SERVER(lo->plh_inode), &fl->deviceid,
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lo->plh_lc_cred, gfp_flags);
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@ -553,8 +557,6 @@ filelayout_check_deviceid(struct pnfs_layout_hdr *lo,
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if (filelayout_test_devid_unavailable(&dsaddr->id_node))
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goto out_put;
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fl->dsaddr = dsaddr;
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if (fl->first_stripe_index >= dsaddr->stripe_count) {
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dprintk("%s Bad first_stripe_index %u\n",
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__func__, fl->first_stripe_index);
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@ -570,6 +572,13 @@ filelayout_check_deviceid(struct pnfs_layout_hdr *lo,
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goto out_put;
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}
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status = 0;
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/*
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* Atomic compare and xchange to ensure we don't scribble
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* over a non-NULL pointer.
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*/
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if (cmpxchg(&fl->dsaddr, NULL, dsaddr) != NULL)
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goto out_put;
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out:
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return status;
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out_put:
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