On Wed, Nov 14 2007, Benny Halevy wrote:
> On Nov. 14, 2007, 13:47 +0200, Jens Axboe <jens.axboe@xxxxxxxxxx> wrote:
> >>From 7b2421e1c075d3c262e28d0598608141add2e7da Mon Sep 17 00:00:00 2001
> > From: Jens Axboe <jens.axboe@xxxxxxxxxx>
> > Date: Wed, 14 Nov 2007 12:36:47 +0100
> > Subject: [PATCH] SG: Convert SCSI to use scatterlist helpers for sg chaining
> >
> > Also change scsi_alloc_sgtable() to just return 0/failure, since it
> > maps to the command passed in. ->request_buffer is now no longer needed,
> > once drivers are adapted to use scsi_sglist() it can be killed.
> >
> > Signed-off-by: Jens Axboe <jens.axboe@xxxxxxxxxx>
> > ---
> > drivers/scsi/scsi_lib.c | 137 ++++++-------------------------------------
> > drivers/scsi/scsi_tgt_lib.c | 3 +-
> > include/scsi/scsi_cmnd.h | 7 +-
> > 3 files changed, 23 insertions(+), 124 deletions(-)
> >
> > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> > index 0e81e4c..1fb3c2e 100644
> > --- a/drivers/scsi/scsi_lib.c
> > +++ b/drivers/scsi/scsi_lib.c
> > @@ -737,138 +737,40 @@ static inline unsigned int scsi_sgtable_index(unsigned short nents)
> > return index;
> > }
> >
> > -struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)
> > +static void scsi_sg_free(struct scatterlist *sgl, unsigned int nents)
> > {
> > struct scsi_host_sg_pool *sgp;
> > - struct scatterlist *sgl, *prev, *ret;
> > - unsigned int index;
> > - int this, left;
> > -
> > - BUG_ON(!cmd->use_sg);
> > -
> > - left = cmd->use_sg;
> > - 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;
> > + sgp = scsi_sg_pools + scsi_sgtable_index(nents);
> > + mempool_free(sgl, sgp->pool);
> > +}
> >
> > - sg_init_table(sgl, sgp->size);
> > +static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
> > +{
> > + struct scsi_host_sg_pool *sgp;
> >
> > - /*
> > - * first loop through, set initial index and return value
> > - */
> > - if (!ret)
> > - ret = sgl;
> > + sgp = scsi_sg_pools + scsi_sgtable_index(nents);
> > + return mempool_alloc(sgp->pool, gfp_mask);
> > +}
> >
> > - /*
> > - * 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);
> > +int scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)
> > +{
> > + int ret;
> >
> > - /*
> > - * if we have nothing left, mark the last segment as
> > - * end-of-list
> > - */
> > - if (!left)
> > - sg_mark_end(&sgl[this - 1]);
> > + BUG_ON(!cmd->use_sg);
> >
> > - /*
> > - * 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);
> > + ret = __sg_alloc_table(&cmd->sg_table, cmd->use_sg, gfp_mask,
> > + scsi_sg_alloc, scsi_sg_free);
> >
> > - /*
> > - * ->use_sg may get modified after dma mapping has potentially
> > - * shrunk the number of segments, so keep a copy of it for free.
> > - */
> > - cmd->__use_sg = cmd->use_sg;
> > + cmd->request_buffer = cmd->sg_table.sgl;
> > return ret;
> > -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 NULL;
> > }
> >
> > EXPORT_SYMBOL(scsi_alloc_sgtable);
>
> <snip>
>
> > @@ -128,14 +127,14 @@ extern void *scsi_kmap_atomic_sg(struct scatterlist *sg, int sg_count,
> > size_t *offset, size_t *len);
> > extern void scsi_kunmap_atomic_sg(void *virt);
> >
> > -extern struct scatterlist *scsi_alloc_sgtable(struct scsi_cmnd *, gfp_t);
> > +extern int scsi_alloc_sgtable(struct scsi_cmnd *, gfp_t);
>
>
> This becomes even nicer on top of the last sdb patches that Boaz sent:
> http://www.spinics.net/lists/linux-scsi/msg20947.html
> and
> http://www.spinics.net/lists/linux-scsi/msg20948.html
>
> that unexport this scsi_alloc_sgtable and make it look like this:
> +static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb,
> + unsigned short sg_count, gfp_t gfp_mask)
Perfect, that ties in nicely!
--
Jens Axboe
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