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Merge branch 'sg' of git://git.kernel.dk/linux-2.6-block
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* 'sg' of git://git.kernel.dk/linux-2.6-block:
  SG: work with the SCSI fixed maximum allocations.
  SG: Convert SCSI to use scatterlist helpers for sg chaining
  SG: Move functions to lib/scatterlist.c and add sg chaining allocator helpers
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Linus Torvalds committed Jan 28, 2008
2 parents d492819 + 7cedb1f commit 68fbda7
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Showing 6 changed files with 347 additions and 225 deletions.
140 changes: 22 additions & 118 deletions drivers/scsi/scsi_lib.c
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Original file line number Diff line number Diff line change
Expand Up @@ -739,138 +739,43 @@ 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;
sgp = scsi_sg_pools + scsi_sgtable_index(nents);
mempool_free(sgl, sgp->pool);
}

sgl = mempool_alloc(sgp->pool, gfp_mask);
if (unlikely(!sgl))
goto enomem;
static struct scatterlist *scsi_sg_alloc(unsigned int nents, gfp_t gfp_mask)
{
struct scsi_host_sg_pool *sgp;

sg_init_table(sgl, sgp->size);
sgp = scsi_sg_pools + scsi_sgtable_index(nents);
return mempool_alloc(sgp->pool, gfp_mask);
}

/*
* first loop through, set initial index and return value
*/
if (!ret)
ret = sgl;
int scsi_alloc_sgtable(struct scsi_cmnd *cmd, gfp_t gfp_mask)
{
int ret;

/*
* 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);
BUG_ON(!cmd->use_sg);

/*
* if we have nothing left, mark the last segment as
* end-of-list
*/
if (!left)
sg_mark_end(&sgl[this - 1]);
ret = __sg_alloc_table(&cmd->sg_table, cmd->use_sg,
SCSI_MAX_SG_SEGMENTS, gfp_mask, scsi_sg_alloc);
if (unlikely(ret))
__sg_free_table(&cmd->sg_table, SCSI_MAX_SG_SEGMENTS,
scsi_sg_free);

/*
* 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.
*/
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);

void scsi_free_sgtable(struct scsi_cmnd *cmd)
{
struct scatterlist *sgl = cmd->request_buffer;
struct scsi_host_sg_pool *sgp;

/*
* if this is the biggest size sglist, check if we have
* chained parts we need to free
*/
if (cmd->__use_sg > SCSI_MAX_SG_SEGMENTS) {
unsigned short this, left;
struct scatterlist *next;
unsigned int index;

left = cmd->__use_sg - (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 = cmd->request_buffer;
sgp = scsi_sg_pools + SG_MEMPOOL_NR - 1;
} else
sgp = scsi_sg_pools + scsi_sgtable_index(cmd->__use_sg);

mempool_free(sgl, sgp->pool);
__sg_free_table(&cmd->sg_table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free);
}

EXPORT_SYMBOL(scsi_free_sgtable);
Expand Down Expand Up @@ -1120,8 +1025,7 @@ static int scsi_init_io(struct scsi_cmnd *cmd)
/*
* If sg table allocation fails, requeue request later.
*/
cmd->request_buffer = scsi_alloc_sgtable(cmd, GFP_ATOMIC);
if (unlikely(!cmd->request_buffer)) {
if (unlikely(scsi_alloc_sgtable(cmd, GFP_ATOMIC))) {
scsi_unprep_request(req);
return BLKPREP_DEFER;
}
Expand Down
3 changes: 1 addition & 2 deletions drivers/scsi/scsi_tgt_lib.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -359,8 +359,7 @@ static int scsi_tgt_init_cmd(struct scsi_cmnd *cmd, gfp_t gfp_mask)
int count;

cmd->use_sg = rq->nr_phys_segments;
cmd->request_buffer = scsi_alloc_sgtable(cmd, gfp_mask);
if (!cmd->request_buffer)
if (scsi_alloc_sgtable(cmd, gfp_mask))
return -ENOMEM;

cmd->request_bufflen = rq->data_len;
Expand Down
126 changes: 26 additions & 100 deletions include/linux/scatterlist.h
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,12 @@
#include <linux/string.h>
#include <asm/io.h>

struct sg_table {
struct scatterlist *sgl; /* the list */
unsigned int nents; /* number of mapped entries */
unsigned int orig_nents; /* original size of list */
};

/*
* Notes on SG table design.
*
Expand Down Expand Up @@ -106,71 +112,12 @@ static inline void sg_set_buf(struct scatterlist *sg, const void *buf,
sg_set_page(sg, virt_to_page(buf), buflen, offset_in_page(buf));
}

/**
* sg_next - return the next scatterlist entry in a list
* @sg: The current sg entry
*
* Description:
* Usually the next entry will be @sg@ + 1, but if this sg element is part
* of a chained scatterlist, it could jump to the start of a new
* scatterlist array.
*
**/
static inline struct scatterlist *sg_next(struct scatterlist *sg)
{
#ifdef CONFIG_DEBUG_SG
BUG_ON(sg->sg_magic != SG_MAGIC);
#endif
if (sg_is_last(sg))
return NULL;

sg++;
if (unlikely(sg_is_chain(sg)))
sg = sg_chain_ptr(sg);

return sg;
}

/*
* Loop over each sg element, following the pointer to a new list if necessary
*/
#define for_each_sg(sglist, sg, nr, __i) \
for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg))

/**
* sg_last - return the last scatterlist entry in a list
* @sgl: First entry in the scatterlist
* @nents: Number of entries in the scatterlist
*
* Description:
* Should only be used casually, it (currently) scan the entire list
* to get the last entry.
*
* Note that the @sgl@ pointer passed in need not be the first one,
* the important bit is that @nents@ denotes the number of entries that
* exist from @sgl@.
*
**/
static inline struct scatterlist *sg_last(struct scatterlist *sgl,
unsigned int nents)
{
#ifndef ARCH_HAS_SG_CHAIN
struct scatterlist *ret = &sgl[nents - 1];
#else
struct scatterlist *sg, *ret = NULL;
unsigned int i;

for_each_sg(sgl, sg, nents, i)
ret = sg;

#endif
#ifdef CONFIG_DEBUG_SG
BUG_ON(sgl[0].sg_magic != SG_MAGIC);
BUG_ON(!sg_is_last(ret));
#endif
return ret;
}

/**
* sg_chain - Chain two sglists together
* @prv: First scatterlist
Expand Down Expand Up @@ -222,47 +169,6 @@ static inline void sg_mark_end(struct scatterlist *sg)
sg->page_link &= ~0x01;
}

/**
* sg_init_table - Initialize SG table
* @sgl: The SG table
* @nents: Number of entries in table
*
* Notes:
* If this is part of a chained sg table, sg_mark_end() should be
* used only on the last table part.
*
**/
static inline void sg_init_table(struct scatterlist *sgl, unsigned int nents)
{
memset(sgl, 0, sizeof(*sgl) * nents);
#ifdef CONFIG_DEBUG_SG
{
unsigned int i;
for (i = 0; i < nents; i++)
sgl[i].sg_magic = SG_MAGIC;
}
#endif
sg_mark_end(&sgl[nents - 1]);
}

/**
* sg_init_one - Initialize a single entry sg list
* @sg: SG entry
* @buf: Virtual address for IO
* @buflen: IO length
*
* Notes:
* This should not be used on a single entry that is part of a larger
* table. Use sg_init_table() for that.
*
**/
static inline void sg_init_one(struct scatterlist *sg, const void *buf,
unsigned int buflen)
{
sg_init_table(sg, 1);
sg_set_buf(sg, buf, buflen);
}

/**
* sg_phys - Return physical address of an sg entry
* @sg: SG entry
Expand Down Expand Up @@ -293,4 +199,24 @@ static inline void *sg_virt(struct scatterlist *sg)
return page_address(sg_page(sg)) + sg->offset;
}

struct scatterlist *sg_next(struct scatterlist *);
struct scatterlist *sg_last(struct scatterlist *s, unsigned int);
void sg_init_table(struct scatterlist *, unsigned int);
void sg_init_one(struct scatterlist *, const void *, 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 *);
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, gfp_t);

/*
* Maximum number of entries that will be allocated in one piece, if
* a list larger than this is required then chaining will be utilized.
*/
#define SG_MAX_SINGLE_ALLOC (PAGE_SIZE / sizeof(struct scatterlist))

#endif /* _LINUX_SCATTERLIST_H */
7 changes: 3 additions & 4 deletions include/scsi/scsi_cmnd.h
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,6 @@
#include <linux/scatterlist.h>

struct request;
struct scatterlist;
struct Scsi_Host;
struct scsi_device;

Expand Down Expand Up @@ -68,8 +67,8 @@ struct scsi_cmnd {
void *request_buffer; /* Actual requested buffer */

/* These elements define the operation we ultimately want to perform */
struct sg_table sg_table;
unsigned short use_sg; /* Number of pieces of scatter-gather */
unsigned short __use_sg;

unsigned underflow; /* Return error if less than
this amount is transferred */
Expand Down Expand Up @@ -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);
extern void scsi_free_sgtable(struct scsi_cmnd *);

extern int scsi_dma_map(struct scsi_cmnd *cmd);
extern void scsi_dma_unmap(struct scsi_cmnd *cmd);

#define scsi_sg_count(cmd) ((cmd)->use_sg)
#define scsi_sglist(cmd) ((struct scatterlist *)(cmd)->request_buffer)
#define scsi_sglist(cmd) ((cmd)->sg_table.sgl)
#define scsi_bufflen(cmd) ((cmd)->request_bufflen)

static inline void scsi_set_resid(struct scsi_cmnd *cmd, int resid)
Expand Down
2 changes: 1 addition & 1 deletion lib/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
rbtree.o radix-tree.o dump_stack.o \
idr.o int_sqrt.o extable.o prio_tree.o \
sha1.o irq_regs.o reciprocal_div.o argv_split.o \
proportions.o prio_heap.o
proportions.o prio_heap.o scatterlist.o

lib-$(CONFIG_MMU) += ioremap.o
lib-$(CONFIG_SMP) += cpumask.o
Expand Down
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