From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCH 12/14] scatterlist: allow chaining to preallocated chunks Date: Wed, 09 Jul 2014 13:21:27 +0200 Message-ID: <53BD25B7.9040302@suse.de> References: <1403715121-1201-1-git-send-email-hch@lst.de> <1403715121-1201-13-git-send-email-hch@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <1403715121-1201-13-git-send-email-hch@lst.de> Sender: linux-kernel-owner@vger.kernel.org To: Christoph Hellwig , James Bottomley Cc: Jens Axboe , Bart Van Assche , Robert Elliott , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-scsi@vger.kernel.org On 06/25/2014 06:51 PM, Christoph Hellwig wrote: > Blk-mq drivers usually preallocate their S/G list as part of the requ= est, > but if we want to support the very large S/G lists currently supporte= d by > the SCSI code that would tie up a lot of memory in the preallocated r= equest > pool. Add support to the scatterlist code so that it can initialize = a > S/G list that uses a preallocated first chunks and dynamically alloca= ted > additional chunks. That way the scsi-mq code can preallocate a first > page worth of S/G entries as part of the request, and dynamically ext= ent > the S/G list when needed. > > Signed-off-by: Christoph Hellwig > --- > drivers/scsi/scsi_lib.c | 16 +++++++--------- > include/linux/scatterlist.h | 6 +++--- > lib/scatterlist.c | 24 ++++++++++++++++-------- > 3 files changed, 26 insertions(+), 20 deletions(-) > > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > index 58534fd..900b1c0 100644 > --- a/drivers/scsi/scsi_lib.c > +++ b/drivers/scsi/scsi_lib.c > @@ -567,6 +567,11 @@ static struct scatterlist *scsi_sg_alloc(unsigne= d int nents, gfp_t gfp_mask) > return mempool_alloc(sgp->pool, gfp_mask); > } > > +static void scsi_free_sgtable(struct scsi_data_buffer *sdb) > +{ > + __sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, false, scsi_sg_f= ree); > +} > + > static int scsi_alloc_sgtable(struct scsi_data_buffer *sdb, int nen= ts, > gfp_t gfp_mask) > { > @@ -575,19 +580,12 @@ static int scsi_alloc_sgtable(struct scsi_data_= buffer *sdb, int nents, > BUG_ON(!nents); > > ret =3D __sg_alloc_table(&sdb->table, nents, SCSI_MAX_SG_SEGMENTS, > - gfp_mask, scsi_sg_alloc); > + NULL, gfp_mask, scsi_sg_alloc); > if (unlikely(ret)) > - __sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, > - scsi_sg_free); > - > + scsi_free_sgtable(sdb); > return ret; > } > > -static void scsi_free_sgtable(struct scsi_data_buffer *sdb) > -{ > - __sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free); > -} > - > /* > * Function: scsi_release_buffers() > * > diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.= h > index a964f72..f4ec8bb 100644 > --- a/include/linux/scatterlist.h > +++ b/include/linux/scatterlist.h > @@ -229,10 +229,10 @@ void sg_init_one(struct scatterlist *, const vo= id *, unsigned int); > typedef struct scatterlist *(sg_alloc_fn)(unsigned int, gfp_t); > typedef void (sg_free_fn)(struct scatterlist *, unsigned int); > > -void __sg_free_table(struct sg_table *, unsigned int, sg_free_fn *); > +void __sg_free_table(struct sg_table *, unsigned int, bool, sg_free_= fn *); > void sg_free_table(struct sg_table *); > -int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, = gfp_t, > - sg_alloc_fn *); > +int __sg_alloc_table(struct sg_table *, unsigned int, unsigned int, > + struct scatterlist *, gfp_t, sg_alloc_fn *); > int sg_alloc_table(struct sg_table *, unsigned int, gfp_t); > int sg_alloc_table_from_pages(struct sg_table *sgt, > struct page **pages, unsigned int n_pages, > diff --git a/lib/scatterlist.c b/lib/scatterlist.c > index 3a8e8e8..48c15d2 100644 > --- a/lib/scatterlist.c > +++ b/lib/scatterlist.c > @@ -165,6 +165,7 @@ static void sg_kfree(struct scatterlist *sg, unsi= gned int nents) > * __sg_free_table - Free a previously mapped sg table > * @table: The sg table header to use > * @max_ents: The maximum number of entries per single scatterlist > + * @skip_first_chunk: don't free the (preallocated) first scatterlis= t chunk > * @free_fn: Free function > * > * Description: > @@ -174,7 +175,7 @@ static void sg_kfree(struct scatterlist *sg, unsi= gned int nents) > * > **/ > void __sg_free_table(struct sg_table *table, unsigned int max_ents, > - sg_free_fn *free_fn) > + bool skip_first_chunk, sg_free_fn *free_fn) > { > struct scatterlist *sgl, *next; > > @@ -202,7 +203,9 @@ void __sg_free_table(struct sg_table *table, unsi= gned int max_ents, > } > > table->orig_nents -=3D sg_size; > - free_fn(sgl, alloc_size); > + if (!skip_first_chunk) > + free_fn(sgl, alloc_size); > + skip_first_chunk =3D false; > sgl =3D next; > } > > @@ -217,7 +220,7 @@ EXPORT_SYMBOL(__sg_free_table); > **/ > void sg_free_table(struct sg_table *table) > { > - __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); > + __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree); > } > EXPORT_SYMBOL(sg_free_table); > > @@ -241,8 +244,8 @@ EXPORT_SYMBOL(sg_free_table); > * > **/ > int __sg_alloc_table(struct sg_table *table, unsigned int nents, > - unsigned int max_ents, gfp_t gfp_mask, > - sg_alloc_fn *alloc_fn) > + unsigned int max_ents, struct scatterlist *first_chunk, > + gfp_t gfp_mask, sg_alloc_fn *alloc_fn) > { > struct scatterlist *sg, *prv; > unsigned int left; > @@ -269,7 +272,12 @@ int __sg_alloc_table(struct sg_table *table, uns= igned int nents, > > left -=3D sg_size; > > - sg =3D alloc_fn(alloc_size, gfp_mask); > + if (first_chunk) { > + sg =3D first_chunk; > + first_chunk =3D NULL; > + } else { > + sg =3D alloc_fn(alloc_size, gfp_mask); > + } > if (unlikely(!sg)) { > /* > * Adjust entry count to reflect that the last > @@ -324,9 +332,9 @@ int sg_alloc_table(struct sg_table *table, unsign= ed int nents, gfp_t gfp_mask) > int ret; > > ret =3D __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, > - gfp_mask, sg_kmalloc); > + NULL, gfp_mask, sg_kmalloc); > if (unlikely(ret)) > - __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); > + __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree); > > return ret; > } > Reviewed-by: Hannes Reinecke Cheers, Hannes --=20 Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=FCrnberg GF: J. Hawn, J. Guild, F. Imend=F6rffer, HRB 16746 (AG N=FCrnberg)