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Diffstat (limited to 'lib/scatterlist.c')
-rw-r--r-- | lib/scatterlist.c | 519 |
1 files changed, 519 insertions, 0 deletions
diff --git a/lib/scatterlist.c b/lib/scatterlist.c new file mode 100644 index 00000000..4ceb05d7 --- /dev/null +++ b/lib/scatterlist.c @@ -0,0 +1,519 @@ +/* + * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com> + * + * Scatterlist handling helpers. + * + * This source code is licensed under the GNU General Public License, + * Version 2. See the file COPYING for more details. + */ +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/scatterlist.h> +#include <linux/highmem.h> +#include <linux/kmemleak.h> + +/** + * 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. + * + **/ +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; +} +EXPORT_SYMBOL(sg_next); + +/** + * 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) scans 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@. + * + **/ +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; +} +EXPORT_SYMBOL(sg_last); + +/** + * 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. + * + **/ +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]); +} +EXPORT_SYMBOL(sg_init_table); + +/** + * sg_init_one - Initialize a single entry sg list + * @sg: SG entry + * @buf: Virtual address for IO + * @buflen: IO length + * + **/ +void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) +{ + sg_init_table(sg, 1); + sg_set_buf(sg, buf, buflen); +} +EXPORT_SYMBOL(sg_init_one); + +/* + * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree + * helpers. + */ +static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask) +{ + if (nents == SG_MAX_SINGLE_ALLOC) { + /* + * Kmemleak doesn't track page allocations as they are not + * commonly used (in a raw form) for kernel data structures. + * As we chain together a list of pages and then a normal + * kmalloc (tracked by kmemleak), in order to for that last + * allocation not to become decoupled (and thus a + * false-positive) we need to inform kmemleak of all the + * intermediate allocations. + */ + void *ptr = (void *) __get_free_page(gfp_mask); + kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask); + return ptr; + } else + return kmalloc(nents * sizeof(struct scatterlist), gfp_mask); +} + +static void sg_kfree(struct scatterlist *sg, unsigned int nents) +{ + if (nents == SG_MAX_SINGLE_ALLOC) { + kmemleak_free(sg); + free_page((unsigned long) sg); + } else + kfree(sg); +} + +/** + * __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(). The @max_ents value must be identical to + * that previously used with __sg_alloc_table(). + * + **/ +void __sg_free_table(struct sg_table *table, unsigned int max_ents, + sg_free_fn *free_fn) +{ + struct scatterlist *sgl, *next; + + if (unlikely(!table->sgl)) + return; + + sgl = table->sgl; + while (table->orig_nents) { + unsigned int alloc_size = table->orig_nents; + unsigned int sg_size; + + /* + * 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 > max_ents) { + next = sg_chain_ptr(&sgl[max_ents - 1]); + alloc_size = max_ents; + sg_size = alloc_size - 1; + } else { + sg_size = alloc_size; + next = NULL; + } + + table->orig_nents -= sg_size; + free_fn(sgl, alloc_size); + sgl = next; + } + + table->sgl = NULL; +} +EXPORT_SYMBOL(__sg_free_table); + +/** + * sg_free_table - Free a previously allocated sg table + * @table: The mapped sg table header + * + **/ +void sg_free_table(struct sg_table *table) +{ + __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); +} +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, + 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 > max_ents); +#endif + + memset(table, 0, sizeof(*table)); + + left = nents; + prv = NULL; + do { + unsigned int sg_size, alloc_size = left; + + if (alloc_size > max_ents) { + alloc_size = max_ents; + sg_size = alloc_size - 1; + } else + sg_size = alloc_size; + + left -= sg_size; + + sg = alloc_fn(alloc_size, gfp_mask); + if (unlikely(!sg)) { + /* + * Adjust entry count to reflect that the last + * entry of the previous table won't be used for + * linkage. Without this, sg_kfree() may get + * confused. + */ + if (prv) + table->nents = ++table->orig_nents; + + return -ENOMEM; + } + + sg_init_table(sg, alloc_size); + table->nents = table->orig_nents += sg_size; + + /* + * If this is the first mapping, assign the sg table header. + * If this is not the first mapping, chain previous part. + */ + if (prv) + sg_chain(prv, max_ents, sg); + else + table->sgl = sg; + + /* + * If no more entries after this one, mark the end + */ + if (!left) + sg_mark_end(&sg[sg_size - 1]); + + /* + * only really needed for mempool backed sg allocations (like + * SCSI), a possible improvement here would be to pass the + * table pointer into the allocator and let that clear these + * flags + */ + gfp_mask &= ~__GFP_WAIT; + gfp_mask |= __GFP_HIGH; + prv = sg; + } while (left); + + return 0; +} +EXPORT_SYMBOL(__sg_alloc_table); + +/** + * sg_alloc_table - Allocate and initialize an sg table + * @table: The sg table header to use + * @nents: Number of entries in sg list + * @gfp_mask: GFP allocation mask + * + * Description: + * Allocate and initialize an sg table. If @nents@ is larger than + * SG_MAX_SINGLE_ALLOC a chained sg table will be setup. + * + **/ +int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) +{ + int ret; + + ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, + gfp_mask, sg_kmalloc); + if (unlikely(ret)) + __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); + + return ret; +} +EXPORT_SYMBOL(sg_alloc_table); + +/** + * sg_miter_start - start mapping iteration over a sg list + * @miter: sg mapping iter to be started + * @sgl: sg list to iterate over + * @nents: number of sg entries + * + * Description: + * Starts mapping iterator @miter. + * + * Context: + * Don't care. + */ +void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, + unsigned int nents, unsigned int flags) +{ + memset(miter, 0, sizeof(struct sg_mapping_iter)); + + miter->__sg = sgl; + miter->__nents = nents; + miter->__offset = 0; + WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); + miter->__flags = flags; +} +EXPORT_SYMBOL(sg_miter_start); + +/** + * sg_miter_next - proceed mapping iterator to the next mapping + * @miter: sg mapping iter to proceed + * + * Description: + * Proceeds @miter@ to the next mapping. @miter@ should have been + * started using sg_miter_start(). On successful return, + * @miter@->page, @miter@->addr and @miter@->length point to the + * current mapping. + * + * Context: + * IRQ disabled if SG_MITER_ATOMIC. IRQ must stay disabled till + * @miter@ is stopped. May sleep if !SG_MITER_ATOMIC. + * + * Returns: + * true if @miter contains the next mapping. false if end of sg + * list is reached. + */ +bool sg_miter_next(struct sg_mapping_iter *miter) +{ + unsigned int off, len; + + /* check for end and drop resources from the last iteration */ + if (!miter->__nents) + return false; + + sg_miter_stop(miter); + + /* get to the next sg if necessary. __offset is adjusted by stop */ + while (miter->__offset == miter->__sg->length) { + if (--miter->__nents) { + miter->__sg = sg_next(miter->__sg); + miter->__offset = 0; + } else + return false; + } + + /* map the next page */ + off = miter->__sg->offset + miter->__offset; + len = miter->__sg->length - miter->__offset; + + miter->page = nth_page(sg_page(miter->__sg), off >> PAGE_SHIFT); + off &= ~PAGE_MASK; + miter->length = min_t(unsigned int, len, PAGE_SIZE - off); + miter->consumed = miter->length; + + if (miter->__flags & SG_MITER_ATOMIC) + miter->addr = kmap_atomic(miter->page, KM_BIO_SRC_IRQ) + off; + else + miter->addr = kmap(miter->page) + off; + + return true; +} +EXPORT_SYMBOL(sg_miter_next); + +/** + * sg_miter_stop - stop mapping iteration + * @miter: sg mapping iter to be stopped + * + * Description: + * Stops mapping iterator @miter. @miter should have been started + * started using sg_miter_start(). A stopped iteration can be + * resumed by calling sg_miter_next() on it. This is useful when + * resources (kmap) need to be released during iteration. + * + * Context: + * IRQ disabled if the SG_MITER_ATOMIC is set. Don't care otherwise. + */ +void sg_miter_stop(struct sg_mapping_iter *miter) +{ + WARN_ON(miter->consumed > miter->length); + + /* drop resources from the last iteration */ + if (miter->addr) { + miter->__offset += miter->consumed; + + if (miter->__flags & SG_MITER_TO_SG) + flush_kernel_dcache_page(miter->page); + + if (miter->__flags & SG_MITER_ATOMIC) { + WARN_ON(!irqs_disabled()); + kunmap_atomic(miter->addr, KM_BIO_SRC_IRQ); + } else + kunmap(miter->page); + + miter->page = NULL; + miter->addr = NULL; + miter->length = 0; + miter->consumed = 0; + } +} +EXPORT_SYMBOL(sg_miter_stop); + +/** + * sg_copy_buffer - Copy data between a linear buffer and an SG list + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy from + * @buflen: The number of bytes to copy + * @to_buffer: transfer direction (non zero == from an sg list to a + * buffer, 0 == from a buffer to an sg list + * + * Returns the number of copied bytes. + * + **/ +static size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, + void *buf, size_t buflen, int to_buffer) +{ + unsigned int offset = 0; + struct sg_mapping_iter miter; + unsigned long flags; + unsigned int sg_flags = SG_MITER_ATOMIC; + + if (to_buffer) + sg_flags |= SG_MITER_FROM_SG; + else + sg_flags |= SG_MITER_TO_SG; + + sg_miter_start(&miter, sgl, nents, sg_flags); + + local_irq_save(flags); + + while (sg_miter_next(&miter) && offset < buflen) { + unsigned int len; + + len = min(miter.length, buflen - offset); + + if (to_buffer) + memcpy(buf + offset, miter.addr, len); + else + memcpy(miter.addr, buf + offset, len); + + offset += len; + } + + sg_miter_stop(&miter); + + local_irq_restore(flags); + return offset; +} + +/** + * sg_copy_from_buffer - Copy from a linear buffer to an SG list + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy from + * @buflen: The number of bytes to copy + * + * Returns the number of copied bytes. + * + **/ +size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, + void *buf, size_t buflen) +{ + return sg_copy_buffer(sgl, nents, buf, buflen, 0); +} +EXPORT_SYMBOL(sg_copy_from_buffer); + +/** + * sg_copy_to_buffer - Copy from an SG list to a linear buffer + * @sgl: The SG list + * @nents: Number of SG entries + * @buf: Where to copy to + * @buflen: The number of bytes to copy + * + * Returns the number of copied bytes. + * + **/ +size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, + void *buf, size_t buflen) +{ + return sg_copy_buffer(sgl, nents, buf, buflen, 1); +} +EXPORT_SYMBOL(sg_copy_to_buffer); |