Re: [PATCH 2/3] SG: Convert SCSI to use scatterlist helpers for sg chaining

Boaz Harrosh
2007-12-20T14:38:46Z

On Thu, Dec 20 2007 at 16:03 +0200, Boaz Harrosh <bharrosh@panasas.com> wrote:
> From: Jens Axboe <jens.axboe@oracle.com>
>
> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
> ---
> drivers/scsi/libsrp.c | 2 +-
> drivers/scsi/scsi_error.c | 4 +-
> drivers/scsi/scsi_lib.c | 150 +++++-------------------------------------
> drivers/usb/storage/isd200.c | 4 +-
> include/scsi/scsi_cmnd.h | 9 +--
> 5 files changed, 24 insertions(+), 145 deletions(-)
>
> diff --git a/drivers/scsi/libsrp.c b/drivers/scsi/libsrp.c
> index 8a8562a..b81350d 100644
> --- a/drivers/scsi/libsrp.c
> +++ b/drivers/scsi/libsrp.c
> @@ -427,7 +427,7 @@ int srp_cmd_queue(struct Scsi_Host *shost, struct srp_cmd *cmd, void *info,
> sc->SCp.ptr = info;
> memcpy(sc->cmnd, cmd->cdb, MAX_COMMAND_SIZE);
> sc->sdb.length = len;
> - sc->sdb.sglist = (void *) (unsigned long) addr;
> + sc->sdb.sgt.sgl = (void *) (unsigned long) addr;
> sc->tag = tag;
> err = scsi_tgt_queue_command(sc, itn_id, (struct scsi_lun *)&cmd->lun,
> cmd->tag);
> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> index 5c8ba6a..1fd2a8c 100644
> --- a/drivers/scsi/scsi_error.c
> +++ b/drivers/scsi/scsi_error.c
> @@ -629,9 +629,9 @@ void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd, struct scsi_eh_save *ses,
> sizeof(scmd->sense_buffer), sense_bytes);
> sg_init_one(&ses->sense_sgl, scmd->sense_buffer,
> scmd->sdb.length);
> - scmd->sdb.sglist = &ses->sense_sgl;
> + scmd->sdb.sgt.sgl = &ses->sense_sgl;
> scmd->sc_data_direction = DMA_FROM_DEVICE;
> - scmd->sdb.sg_count = 1;
> + scmd->sdb.sgt.nents = 1;
> memset(scmd->cmnd, 0, sizeof(scmd->cmnd));
> scmd->cmnd[0] = REQUEST_SENSE;
> scmd->cmnd[4] = scmd->sdb.length;
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index a6aae56..c7107f1 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -750,136 +750,15 @@ static inline unsigned int scsi_sgtable_index(unsigned short nents)
> return index;
> }
>
> -static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb,
> - unsigned short sg_count, gfp_t gfp_mask)
> +static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
> {
> - struct scsi_host_sg_pool *sgp;
> - struct scatterlist *sgl, *prev, *ret;
> - unsigned int index;
> - int this, left;
> -
> - left = sg_count;
> - ret = prev = NULL;
> - do {
> - this = left;
> - if (this > SCSI_MAX_SG_SEGMENTS) {
> - this = SCSI_MAX_SG_SEGMENTS - 1;
> - index = SG_MEMPOOL_NR - 1;
> - } else
> - index = scsi_sgtable_index(this);
> -
> - left -= this;
> -
> - sgp = scsi_sg_pools + index;
> -
> - sgl = mempool_alloc(sgp->pool, gfp_mask);
> - if (unlikely(!sgl))
> - goto enomem;
> -
> - sg_init_table(sgl, sgp->size);
> -
> - /*
> - * first loop through, set initial index and return value
> - */
> - if (!ret)
> - ret = sgl;
> -
> - /*
> - * chain previous sglist, if any. we know the previous
> - * sglist must be the biggest one, or we would not have
> - * ended up doing another loop.
> - */
> - if (prev)
> - sg_chain(prev, SCSI_MAX_SG_SEGMENTS, sgl);
> -
> - /*
> - * if we have nothing left, mark the last segment as
> - * end-of-list
> - */
> - if (!left)
> - sg_mark_end(&sgl[this - 1]);
> -
> - /*
> - * don't allow subsequent mempool allocs to sleep, it would
> - * violate the mempool principle.
> - */
> - gfp_mask &= ~__GFP_WAIT;
> - gfp_mask |= __GFP_HIGH;
> - prev = sgl;
> - } while (left);
> -
> - /*
> - * ->use_sg may get modified after dma mapping has potentially
> - * shrunk the number of segments, so keep a copy of it for free.
> - */
> - sdb->alloc_sg_count = sdb->sg_count = sg_count;
> - sdb->sglist = ret;
> - return 0;
> -enomem:
> - if (ret) {
> - /*
> - * Free entries chained off ret. Since we were trying to
> - * allocate another sglist, we know that all entries are of
> - * the max size.
> - */
> - sgp = scsi_sg_pools + SG_MEMPOOL_NR - 1;
> - prev = ret;
> - ret = &ret[SCSI_MAX_SG_SEGMENTS - 1];
> -
> - while ((sgl = sg_chain_ptr(ret)) != NULL) {
> - ret = &sgl[SCSI_MAX_SG_SEGMENTS - 1];
> - mempool_free(sgl, sgp->pool);
> - }
> -
> - mempool_free(prev, sgp->pool);
> - }
> - return -ENOMEM;
> + return mempool_alloc(scsi_sg_pools[scsi_sgtable_index(nents)].pool,
> + gfp_mask);
> }
>
> -static void scsi_free_sgtable(struct scsi_data_buffer *sdb)
> +static void scsi_sg_free(struct scatterlist *sgl, unsigned int nents)
> {
> - struct scatterlist *sgl = sdb->sglist;
> - struct scsi_host_sg_pool *sgp;
> -
> - /*
> - * if this is the biggest size sglist, check if we have
> - * chained parts we need to free
> - */
> - if (sdb->alloc_sg_count > SCSI_MAX_SG_SEGMENTS) {
> - unsigned short this, left;
> - struct scatterlist *next;
> - unsigned int index;
> -
> - left = sdb->alloc_sg_count - (SCSI_MAX_SG_SEGMENTS - 1);
> - next = sg_chain_ptr(&sgl[SCSI_MAX_SG_SEGMENTS - 1]);
> - while (left && next) {
> - sgl = next;
> - this = left;
> - if (this > SCSI_MAX_SG_SEGMENTS) {
> - this = SCSI_MAX_SG_SEGMENTS - 1;
> - index = SG_MEMPOOL_NR - 1;
> - } else
> - index = scsi_sgtable_index(this);
> -
> - left -= this;
> -
> - sgp = scsi_sg_pools + index;
> -
> - if (left)
> - next = sg_chain_ptr(&sgl[sgp->size - 1]);
> -
> - mempool_free(sgl, sgp->pool);
> - }
> -
> - /*
> - * Restore original, will be freed below
> - */
> - sgl = sdb->sglist;
> - sgp = scsi_sg_pools + SG_MEMPOOL_NR - 1;
> - } else
> - sgp = scsi_sg_pools + scsi_sgtable_index(sdb->alloc_sg_count);
> -
> - mempool_free(sgl, sgp->pool);
> + mempool_free(sgl, scsi_sg_pools[scsi_sgtable_index(nents)].pool);
> }
>
> /*
> @@ -901,15 +780,15 @@ static void scsi_free_sgtable(struct scsi_data_buffer *sdb)
> */
> void scsi_release_buffers(struct scsi_cmnd *cmd)
> {
> - if (cmd->sdb.sglist)
> - scsi_free_sgtable(&cmd->sdb);
> + if (cmd->sdb.sgt.sgl)
> + __sg_free_table(&cmd->sdb.sgt, scsi_sg_free);
>
> memset(&cmd->sdb, 0, sizeof(cmd->sdb));
>
> if (scsi_bidi_cmnd(cmd)) {
> struct scsi_data_buffer *bidi_sdb =
> cmd->request->next_rq->special;
> - scsi_free_sgtable(bidi_sdb);
> + __sg_free_table(&bidi_sdb->sgt, scsi_sg_free);
> kmem_cache_free(scsi_bidi_sdb_cache, bidi_sdb);
> cmd->request->next_rq->special = NULL;
> }
> @@ -1135,9 +1014,12 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
> static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb,
> gfp_t gfp_mask)
> {
> - int count;
> + int count, ret;
>
> - if (scsi_alloc_sgtable(sdb, req->nr_phys_segments, gfp_mask)) {
> + ret = __sg_alloc_table(&sdb->sgt, req->nr_phys_segments, gfp_mask,
> + scsi_sg_alloc);
> + if (unlikely(ret)) {
> + __sg_free_table(&sdb->sgt, scsi_sg_free);
> return BLKPREP_DEFER;
> }
>
> @@ -1151,9 +1033,9 @@ static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb,
> * Next, walk the list, and fill in the addresses and sizes of
> * each segment.
> */
> - count = blk_rq_map_sg(req->q, req, sdb->sglist);
> - BUG_ON(count > sdb->sg_count);
> - sdb->sg_count = count;
> + count = blk_rq_map_sg(req->q, req, sdb->sgt.sgl);
> + BUG_ON(count > sdb->sgt.nents);
> + sdb->sgt.nents = count;
> return BLKPREP_OK;
> }
>
> diff --git a/drivers/usb/storage/isd200.c b/drivers/usb/storage/isd200.c
> index 2d9a32b..0214ddb 100644
> --- a/drivers/usb/storage/isd200.c
> +++ b/drivers/usb/storage/isd200.c
> @@ -415,9 +415,9 @@ static void isd200_set_srb(struct isd200_info *info,
> sg_init_one(&info->sg, buff, bufflen);
>
> srb->sc_data_direction = dir;
> - srb->sdb.sglist = buff ? &info->sg : NULL;
> + srb->sdb.sgt.sgl = buff ? &info->sg : NULL;
> srb->sdb.length = bufflen;
> - srb->sdb.sg_count = buff ? 1 : 0;
> + srb->sdb.sgt.nents = buff ? 1 : 0;
> }
>
> static void isd200_srb_set_bufflen(struct scsi_cmnd *srb, unsigned bufflen)
> diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
> index cd2851a..9933bbe 100644
> --- a/include/scsi/scsi_cmnd.h
> +++ b/include/scsi/scsi_cmnd.h
> @@ -8,16 +8,13 @@
> #include <linux/timer.h>
> #include <linux/scatterlist.h>
>
> -struct scatterlist;
> struct Scsi_Host;
> struct scsi_device;
>
> struct scsi_data_buffer {
> - struct scatterlist *sglist;
> + struct sg_table sgt;
> unsigned length;
> int resid;
> - unsigned short sg_count;
> - unsigned short alloc_sg_count; /* private to scsi_lib */
> };
>
> /* embedded in scsi_cmnd */
> @@ -136,12 +133,12 @@ extern void scsi_dma_unmap(struct scsi_cmnd *cmd);
>
> static inline unsigned scsi_sg_count(struct scsi_cmnd *cmd)
> {
> - return cmd->sdb.sg_count;
> + return cmd->sdb.sgt.nents;
> }
>
> static inline struct scatterlist *scsi_sglist(struct scsi_cmnd *cmd)
> {
> - return cmd->sdb.sglist;
> + return cmd->sdb.sgt.sgl;
> }
>
> static inline unsigned scsi_bufflen(struct scsi_cmnd *cmd)

The cmd->sdb.sgt.sgl thingy is a bit ugly, I would say. There is
not much we can do, unless Jens is willing to add the "length" and
"resid" members into his struct sg_table. I guess other drivers might
have use for them other than scsi. Jens could you do this for us?

Boaz