On Nov. 10, 2008, 22:21 +0200, Benny Halevy <bhalevy@xxxxxxxxxxx> wrote:
> Find a free slot using bitmap-based allocation.
> Use the optimized ffz function to find a zero bit
> in the bitmap that indicates a free slot, starting
> the search from the 'lowest_free_slotid' position.
>
> If found, mark the slot as used in the bitmap, get
> the slot's slotid and seqid, and update max_slotid
> to be used by the SEQUENCE operation.
>
> Also, update lowest_free_slotid for next search.
>
> If no free slot was found the caller has to wait
> for a free slot (outside the scope of this function)
>
> Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx>
> ---
> fs/nfs/nfs4proc.c | 88 ++++++++++++++++++++++++++++++++++++++++++
> include/linux/nfs4_session.h | 5 ++
> 2 files changed, 93 insertions(+), 0 deletions(-)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index 08e7129..4ded3a5 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -207,6 +207,94 @@ static void renew_lease(const struct nfs_server *server, unsigned long timestamp
> spin_unlock(&clp->cl_lock);
> }
>
> +#if defined(CONFIG_NFS_V4_1)
> +
> +/*
> + * idx2bmp - return pointer to bitmap word holding index "idx".
> + *
> + * inputs:
> + * @base points to bitmap.
> + * @idx slot index.
> + *
> + * output:
> + * @bit optional, *bit set to bit index of "idx" in the returned
> + * bitmap word.
> + */
> +static inline unsigned long *idx2bmp(unsigned long *base, int idx, int *bit)
> +{
> + base += idx / BITS_PER_LONG;
> + if (bit)
> + *bit = idx & (BITS_PER_LONG - 1);
> + return base;
> +}
> +
> +/*
> + * bmp2idx - return absolute index of bmp:bit in bitmap.
> + *
> + * inputs:
> + * @base points to bitmap.
> + * @bmp points to bitmap word.
> + * @bit bit index in bitmap word.
> + */
> +static inline int bmp2idx(unsigned long *base, unsigned long *bmp,
> + int bit)
> +{
> + return ((bmp - base) * BITS_PER_LONG) + bit;
> +}
> +
> +/*
> + * nfs4_find_slot - efficiently look for a free slot
> + *
> + * nfs4_find_slot uses the ffz cpu-optimized function to look for an unset
> + * bit in each word in the bitmap.
> + * Scan starts at lowest_free_slotid, which is a hint for the free slot,
> + * as all lower-numbered slots are known to be used.
> + * If found, we mark the slot as used, update the highest_used_slotid,
> + * and respectively set up the sequence operation args.
> + * The lowest_free_slotid is always set to the successive slotid.
> + * A pointer to the slot's seqid is returned if found, or NULL otherwise.
> + */
> +static struct nfs4_slot *
> +nfs4_find_slot(struct nfs4_slot_table *tbl, struct rpc_task *task)
> +{
> + int bit, slotid;
> + struct nfs4_slot *slot = NULL;
> + unsigned long *used, u;
> +
> + spin_lock(&tbl->slot_tbl_lock);
> + slotid = tbl->lowest_free_slotid;
> + while (slotid < tbl->max_slots) {
> + used = idx2bmp(tbl->used_slots, slotid, NULL);
> + u = *used;
> + if (u == ~0UL) {
> + /* all slots marked used in this word */
> + slotid += BITS_PER_LONG;
> + continue;
> + }
> + /* find first slot marked free in word */
> + bit = ffz(u);
review 11-14: look into using a bitmap_find_free_region function
> + slotid = bmp2idx(tbl->used_slots, used, bit);
> + /* mark slot used. note that we don't do that if
> + * slotid >= tbl->max_slots so not to confuse
> + * highest_used_slotid algorithm */
> + if (slotid < tbl->max_slots) {
> + *used |= (1 << bit);
> + if (slotid > tbl->highest_used_slotid)
> + tbl->highest_used_slotid = slotid;
> + slot = tbl->slots + slotid;
> + slotid++; /* for updating lowest_free_slot */
> + }
> + break;
> + }
> + tbl->lowest_free_slotid = slotid;
> + spin_unlock(&tbl->slot_tbl_lock);
> + dprintk("<-- %s slot %p slotid %d\n", __func__,
> + slot, slot ? slot_idx(tbl, slot) : -1);
> + return slot;
> +}
> +
> +#endif /* CONFIG_NFS_V4_1 */
> +
> static void update_changeattr(struct inode *dir, struct nfs4_change_info *cinfo)
> {
> struct nfs_inode *nfsi = NFS_I(dir);
> diff --git a/include/linux/nfs4_session.h b/include/linux/nfs4_session.h
> index d534269..2960ba9 100644
> --- a/include/linux/nfs4_session.h
> +++ b/include/linux/nfs4_session.h
> @@ -33,6 +33,11 @@ struct nfs4_slot_table {
> * op for dynamic resizing */
> };
>
> +static inline int slot_idx(struct nfs4_slot_table *tbl, struct nfs4_slot *sp)
> +{
> + return sp - tbl->slots;
> +}
> +
> struct nfs4_channel {
> struct nfs4_channel_attrs chan_attrs;
> struct rpc_clnt *rpc_client;
--
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