From e2c4ab3ce2ecc527672bd7e29a594c50d3ec0477 Mon Sep 17 00:00:00 2001 From: Andy Adamson Date: Wed, 1 Apr 2009 09:22:16 -0400 Subject: [PATCH] nfs41: free slot 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 [nfs41: free slot use slotid] Signed-off-by: Andy Adamson Signed-off-by: Benny Halevy [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 [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 [nfs41: use find_last_bit in nfs4_free_slot to determine highest used slot.] Signed-off-by: Benny Halevy [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 Signed-off-by: Trond Myklebust --- fs/nfs/nfs4proc.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index c9618080317e..b6308f6740ec 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -273,6 +273,42 @@ 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 *