From: Andy Adamson <andros@xxxxxxxxxx>
Free a slot in the slot table.
Mark the slot as free in the bitmap-based allocation table
by clearing a bit corresponding to the slotid.
Update lowest_free_slotid if freed slotid is lower than that.
Update highest_used_slotid. In the case the freed slotid
equals the highest_used_slotid, scan downwards for the next
highest used slotid using the optimized fls* functions.
Finally, wake up thread waiting on slot_tbl_waitq for a free slot
to become available.
Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
[nfs41: free slot use slotid]
Signed-off-by: Andy Adamson <andros@xxxxxxxxxx>
Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
[nfs41: use find_first_zero_bit for nfs4_find_slot]
While at it, obliterate lowest_free_slotid and fix-up related comments.
As per review comment 21/85.
Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
[nfs41: use __clear_bit for nfs4_free_slot]
While at it, fix-up function comment.
Part of review comment 22/85.
Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
[nfs41: use find_last_bit in nfs4_free_slot to determine highest used slot.]
Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
[nfs41: rpc_sleep_on slot_tbl_waitq must be called under slot_tbl_lock]
Otherwise there's a race (we've hit) with nfs4_free_slot where
nfs41_setup_sequence sees a full slot table, unlocks slot_tbl_lock,
nfs4_free_slots happen concurrently and call rpc_wake_up_next
where there's nobody to wake up yet, context goes back to
nfs41_setup_sequence which goes to sleep when the slot table
is actually empty now and there's no-one to wake it up anymore.
Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
---
fs/nfs/nfs4proc.c | 36 ++++++++++++++++++++++++++++++++++++
1 files changed, 36 insertions(+), 0 deletions(-)
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 9bc6bb7..fed6cfb 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -282,6 +282,42 @@ static void renew_lease(const struct nfs_server *server, unsigned long timestamp
#if defined(CONFIG_NFS_V4_1)
/*
+ * nfs4_free_slot - free a slot and efficiently update slot table.
+ *
+ * freeing a slot is trivially done by clearing its respective bit
+ * in the bitmap.
+ * If the freed slotid equals highest_used_slotid we want to update it
+ * so that the server would be able to size down the slot table if needed,
+ * otherwise we know that the highest_used_slotid is still in use.
+ * When updating highest_used_slotid there may be "holes" in the bitmap
+ * so we need to scan down from highest_used_slotid to 0 looking for the now
+ * highest slotid in use.
+ * If none found, highest_used_slotid is set to -1.
+ */
+static void
+nfs4_free_slot(struct nfs4_slot_table *tbl, u8 free_slotid)
+{
+ int slotid = free_slotid;
+
+ spin_lock(&tbl->slot_tbl_lock);
+ /* clear used bit in bitmap */
+ __clear_bit(slotid, tbl->used_slots);
+
+ /* update highest_used_slotid when it is freed */
+ if (slotid == tbl->highest_used_slotid) {
+ slotid = find_last_bit(tbl->used_slots, tbl->max_slots);
+ if (slotid >= 0 && slotid < tbl->max_slots)
+ tbl->highest_used_slotid = slotid;
+ else
+ tbl->highest_used_slotid = -1;
+ }
+ rpc_wake_up_next(&tbl->slot_tbl_waitq);
+ spin_unlock(&tbl->slot_tbl_lock);
+ dprintk("%s: free_slotid %u highest_used_slotid %d\n", __func__,
+ free_slotid, tbl->highest_used_slotid);
+}
+
+/*
* nfs4_find_slot - efficiently look for a free slot
*
* nfs4_find_slot looks for an unset bit in the used_slots bitmap.
--
1.6.1.3
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