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NFSv4.1: Ensure that the layout sequence id stays 'close' to the current

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Clamp the layout barrier sequence id to the current sequence id
minus the maximum number of outstanding layoutget requests.

Also ensure that we correctly initialise lo->plh_barrier if there are
no layout segments associated to this layout header.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Trond Myklebust 2012-10-04 16:32:22 -07:00
parent 0f35ad6f68
commit 22aaf71495
1 changed files with 8 additions and 13 deletions
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21
fs/nfs/pnfs.c
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@ -563,28 +563,23 @@ void
pnfs_set_layout_stateid(struct pnfs_layout_hdr *lo, const nfs4_stateid *new,
bool update_barrier)
{
u32 oldseq, newseq;
u32 oldseq, newseq, new_barrier;
int empty = list_empty(&lo->plh_segs);
oldseq = be32_to_cpu(lo->plh_stateid.seqid);
newseq = be32_to_cpu(new->seqid);
if (list_empty(&lo->plh_segs) || pnfs_seqid_is_newer(newseq, oldseq)) {
if (empty || pnfs_seqid_is_newer(newseq, oldseq)) {
nfs4_stateid_copy(&lo->plh_stateid, new);
if (update_barrier) {
u32 new_barrier = be32_to_cpu(new->seqid);
if (pnfs_seqid_is_newer(new_barrier, lo->plh_barrier))
lo->plh_barrier = new_barrier;
new_barrier = be32_to_cpu(new->seqid);
} else {
/* Because of wraparound, we want to keep the barrier
* "close" to the current seqids. It needs to be
* within 2**31 to count as "behind", so if it
* gets too near that limit, give us a litle leeway
* and bring it to within 2**30.
* NOTE - and yes, this is all unsigned arithmetic.
* "close" to the current seqids.
*/
if (unlikely((newseq - lo->plh_barrier) > (3 << 29)))
lo->plh_barrier = newseq - (1 << 30);
new_barrier = newseq - atomic_read(&lo->plh_outstanding);
}
if (empty || pnfs_seqid_is_newer(new_barrier, lo->plh_barrier))
lo->plh_barrier = new_barrier;
}
}