From 7cedb1f17fb7f4374d11501f61656ae9d3ba47e9 Mon Sep 17 00:00:00 2001 From: James Bottomley Date: Sun, 13 Jan 2008 14:15:28 -0600 Subject: SG: work with the SCSI fixed maximum allocations. SCSI sg table allocation has a maximum size (of SCSI_MAX_SG_SEGMENTS, currently 128) and this will cause a BUG_ON() in SCSI if something tries an allocation over it. This patch adds a size limit to the chaining allocator to allow the specification of the maximum allocation size for chaining, so we always chain in units of the maximum SCSI allocation size. Signed-off-by: James Bottomley Signed-off-by: Jens Axboe --- lib/scatterlist.c | 41 +++++++++++++++++++++++++++-------------- 1 file changed, 27 insertions(+), 14 deletions(-) (limited to 'lib') diff --git a/lib/scatterlist.c b/lib/scatterlist.c index 02aaa27e010..acca4901046 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -130,13 +130,17 @@ static void sg_kfree(struct scatterlist *sg, unsigned 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 * @free_fn: Free function * * Description: - * Free an sg table previously allocated and setup with __sg_alloc_table(). + * Free an sg table previously allocated and setup with + * __sg_alloc_table(). The @max_ents value must be identical to + * that previously used with __sg_alloc_table(). * **/ -void __sg_free_table(struct sg_table *table, sg_free_fn *free_fn) +void __sg_free_table(struct sg_table *table, unsigned int max_ents, + sg_free_fn *free_fn) { struct scatterlist *sgl, *next; @@ -149,14 +153,14 @@ void __sg_free_table(struct sg_table *table, sg_free_fn *free_fn) unsigned int sg_size; /* - * If we have more than SG_MAX_SINGLE_ALLOC segments left, + * If we have more than max_ents segments left, * then assign 'next' to the sg table after the current one. * sg_size is then one less than alloc size, since the last * element is the chain pointer. */ - if (alloc_size > SG_MAX_SINGLE_ALLOC) { - next = sg_chain_ptr(&sgl[SG_MAX_SINGLE_ALLOC - 1]); - alloc_size = SG_MAX_SINGLE_ALLOC; + if (alloc_size > max_ents) { + next = sg_chain_ptr(&sgl[max_ents - 1]); + alloc_size = max_ents; sg_size = alloc_size - 1; } else { sg_size = alloc_size; @@ -179,7 +183,7 @@ EXPORT_SYMBOL(__sg_free_table); **/ void sg_free_table(struct sg_table *table) { - __sg_free_table(table, sg_kfree); + __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); } EXPORT_SYMBOL(sg_free_table); @@ -187,22 +191,30 @@ EXPORT_SYMBOL(sg_free_table); * __sg_alloc_table - Allocate and initialize an sg table with given allocator * @table: The sg table header to use * @nents: Number of entries in sg list + * @max_ents: The maximum number of entries the allocator returns per call * @gfp_mask: GFP allocation mask * @alloc_fn: Allocator to use * + * Description: + * This function returns a @table @nents long. The allocator is + * defined to return scatterlist chunks of maximum size @max_ents. + * Thus if @nents is bigger than @max_ents, the scatterlists will be + * chained in units of @max_ents. + * * Notes: * If this function returns non-0 (eg failure), the caller must call * __sg_free_table() to cleanup any leftover allocations. * **/ -int __sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask, +int __sg_alloc_table(struct sg_table *table, unsigned int nents, + unsigned int max_ents, gfp_t gfp_mask, sg_alloc_fn *alloc_fn) { struct scatterlist *sg, *prv; unsigned int left; #ifndef ARCH_HAS_SG_CHAIN - BUG_ON(nents > SG_MAX_SINGLE_ALLOC); + BUG_ON(nents > max_ents); #endif memset(table, 0, sizeof(*table)); @@ -212,8 +224,8 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask, do { unsigned int sg_size, alloc_size = left; - if (alloc_size > SG_MAX_SINGLE_ALLOC) { - alloc_size = SG_MAX_SINGLE_ALLOC; + if (alloc_size > max_ents) { + alloc_size = max_ents; sg_size = alloc_size - 1; } else sg_size = alloc_size; @@ -232,7 +244,7 @@ int __sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask, * If this is not the first mapping, chain previous part. */ if (prv) - sg_chain(prv, SG_MAX_SINGLE_ALLOC, sg); + sg_chain(prv, max_ents, sg); else table->sgl = sg; @@ -272,9 +284,10 @@ int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) { int ret; - ret = __sg_alloc_table(table, nents, gfp_mask, sg_kmalloc); + ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, + gfp_mask, sg_kmalloc); if (unlikely(ret)) - __sg_free_table(table, sg_kfree); + __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); return ret; } -- cgit v1.2.3