10db9299fSJens Axboe /* 20db9299fSJens Axboe * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com> 30db9299fSJens Axboe * 40db9299fSJens Axboe * Scatterlist handling helpers. 50db9299fSJens Axboe * 60db9299fSJens Axboe * This source code is licensed under the GNU General Public License, 70db9299fSJens Axboe * Version 2. See the file COPYING for more details. 80db9299fSJens Axboe */ 90db9299fSJens Axboe #include <linux/module.h> 100db9299fSJens Axboe #include <linux/scatterlist.h> 110db9299fSJens Axboe 120db9299fSJens Axboe /** 130db9299fSJens Axboe * sg_next - return the next scatterlist entry in a list 140db9299fSJens Axboe * @sg: The current sg entry 150db9299fSJens Axboe * 160db9299fSJens Axboe * Description: 170db9299fSJens Axboe * Usually the next entry will be @sg@ + 1, but if this sg element is part 180db9299fSJens Axboe * of a chained scatterlist, it could jump to the start of a new 190db9299fSJens Axboe * scatterlist array. 200db9299fSJens Axboe * 210db9299fSJens Axboe **/ 220db9299fSJens Axboe struct scatterlist *sg_next(struct scatterlist *sg) 230db9299fSJens Axboe { 240db9299fSJens Axboe #ifdef CONFIG_DEBUG_SG 250db9299fSJens Axboe BUG_ON(sg->sg_magic != SG_MAGIC); 260db9299fSJens Axboe #endif 270db9299fSJens Axboe if (sg_is_last(sg)) 280db9299fSJens Axboe return NULL; 290db9299fSJens Axboe 300db9299fSJens Axboe sg++; 310db9299fSJens Axboe if (unlikely(sg_is_chain(sg))) 320db9299fSJens Axboe sg = sg_chain_ptr(sg); 330db9299fSJens Axboe 340db9299fSJens Axboe return sg; 350db9299fSJens Axboe } 360db9299fSJens Axboe EXPORT_SYMBOL(sg_next); 370db9299fSJens Axboe 380db9299fSJens Axboe /** 390db9299fSJens Axboe * sg_last - return the last scatterlist entry in a list 400db9299fSJens Axboe * @sgl: First entry in the scatterlist 410db9299fSJens Axboe * @nents: Number of entries in the scatterlist 420db9299fSJens Axboe * 430db9299fSJens Axboe * Description: 440db9299fSJens Axboe * Should only be used casually, it (currently) scans the entire list 450db9299fSJens Axboe * to get the last entry. 460db9299fSJens Axboe * 470db9299fSJens Axboe * Note that the @sgl@ pointer passed in need not be the first one, 480db9299fSJens Axboe * the important bit is that @nents@ denotes the number of entries that 490db9299fSJens Axboe * exist from @sgl@. 500db9299fSJens Axboe * 510db9299fSJens Axboe **/ 520db9299fSJens Axboe struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents) 530db9299fSJens Axboe { 540db9299fSJens Axboe #ifndef ARCH_HAS_SG_CHAIN 550db9299fSJens Axboe struct scatterlist *ret = &sgl[nents - 1]; 560db9299fSJens Axboe #else 570db9299fSJens Axboe struct scatterlist *sg, *ret = NULL; 580db9299fSJens Axboe unsigned int i; 590db9299fSJens Axboe 600db9299fSJens Axboe for_each_sg(sgl, sg, nents, i) 610db9299fSJens Axboe ret = sg; 620db9299fSJens Axboe 630db9299fSJens Axboe #endif 640db9299fSJens Axboe #ifdef CONFIG_DEBUG_SG 650db9299fSJens Axboe BUG_ON(sgl[0].sg_magic != SG_MAGIC); 660db9299fSJens Axboe BUG_ON(!sg_is_last(ret)); 670db9299fSJens Axboe #endif 680db9299fSJens Axboe return ret; 690db9299fSJens Axboe } 700db9299fSJens Axboe EXPORT_SYMBOL(sg_last); 710db9299fSJens Axboe 720db9299fSJens Axboe /** 730db9299fSJens Axboe * sg_init_table - Initialize SG table 740db9299fSJens Axboe * @sgl: The SG table 750db9299fSJens Axboe * @nents: Number of entries in table 760db9299fSJens Axboe * 770db9299fSJens Axboe * Notes: 780db9299fSJens Axboe * If this is part of a chained sg table, sg_mark_end() should be 790db9299fSJens Axboe * used only on the last table part. 800db9299fSJens Axboe * 810db9299fSJens Axboe **/ 820db9299fSJens Axboe void sg_init_table(struct scatterlist *sgl, unsigned int nents) 830db9299fSJens Axboe { 840db9299fSJens Axboe memset(sgl, 0, sizeof(*sgl) * nents); 850db9299fSJens Axboe #ifdef CONFIG_DEBUG_SG 860db9299fSJens Axboe { 870db9299fSJens Axboe unsigned int i; 880db9299fSJens Axboe for (i = 0; i < nents; i++) 890db9299fSJens Axboe sgl[i].sg_magic = SG_MAGIC; 900db9299fSJens Axboe } 910db9299fSJens Axboe #endif 920db9299fSJens Axboe sg_mark_end(&sgl[nents - 1]); 930db9299fSJens Axboe } 940db9299fSJens Axboe EXPORT_SYMBOL(sg_init_table); 950db9299fSJens Axboe 960db9299fSJens Axboe /** 970db9299fSJens Axboe * sg_init_one - Initialize a single entry sg list 980db9299fSJens Axboe * @sg: SG entry 990db9299fSJens Axboe * @buf: Virtual address for IO 1000db9299fSJens Axboe * @buflen: IO length 1010db9299fSJens Axboe * 1020db9299fSJens Axboe **/ 1030db9299fSJens Axboe void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) 1040db9299fSJens Axboe { 1050db9299fSJens Axboe sg_init_table(sg, 1); 1060db9299fSJens Axboe sg_set_buf(sg, buf, buflen); 1070db9299fSJens Axboe } 1080db9299fSJens Axboe EXPORT_SYMBOL(sg_init_one); 1090db9299fSJens Axboe 1100db9299fSJens Axboe /* 1110db9299fSJens Axboe * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree 1120db9299fSJens Axboe * helpers. 1130db9299fSJens Axboe */ 1140db9299fSJens Axboe static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask) 1150db9299fSJens Axboe { 1160db9299fSJens Axboe if (nents == SG_MAX_SINGLE_ALLOC) 1170db9299fSJens Axboe return (struct scatterlist *) __get_free_page(gfp_mask); 1180db9299fSJens Axboe else 1190db9299fSJens Axboe return kmalloc(nents * sizeof(struct scatterlist), gfp_mask); 1200db9299fSJens Axboe } 1210db9299fSJens Axboe 1220db9299fSJens Axboe static void sg_kfree(struct scatterlist *sg, unsigned int nents) 1230db9299fSJens Axboe { 1240db9299fSJens Axboe if (nents == SG_MAX_SINGLE_ALLOC) 1250db9299fSJens Axboe free_page((unsigned long) sg); 1260db9299fSJens Axboe else 1270db9299fSJens Axboe kfree(sg); 1280db9299fSJens Axboe } 1290db9299fSJens Axboe 1300db9299fSJens Axboe /** 1310db9299fSJens Axboe * __sg_free_table - Free a previously mapped sg table 1320db9299fSJens Axboe * @table: The sg table header to use 1337cedb1f1SJames Bottomley * @max_ents: The maximum number of entries per single scatterlist 1340db9299fSJens Axboe * @free_fn: Free function 1350db9299fSJens Axboe * 1360db9299fSJens Axboe * Description: 1377cedb1f1SJames Bottomley * Free an sg table previously allocated and setup with 1387cedb1f1SJames Bottomley * __sg_alloc_table(). The @max_ents value must be identical to 1397cedb1f1SJames Bottomley * that previously used with __sg_alloc_table(). 1400db9299fSJens Axboe * 1410db9299fSJens Axboe **/ 1427cedb1f1SJames Bottomley void __sg_free_table(struct sg_table *table, unsigned int max_ents, 1437cedb1f1SJames Bottomley sg_free_fn *free_fn) 1440db9299fSJens Axboe { 1450db9299fSJens Axboe struct scatterlist *sgl, *next; 1460db9299fSJens Axboe 1470db9299fSJens Axboe if (unlikely(!table->sgl)) 1480db9299fSJens Axboe return; 1490db9299fSJens Axboe 1500db9299fSJens Axboe sgl = table->sgl; 1510db9299fSJens Axboe while (table->orig_nents) { 1520db9299fSJens Axboe unsigned int alloc_size = table->orig_nents; 1530db9299fSJens Axboe unsigned int sg_size; 1540db9299fSJens Axboe 1550db9299fSJens Axboe /* 1567cedb1f1SJames Bottomley * If we have more than max_ents segments left, 1570db9299fSJens Axboe * then assign 'next' to the sg table after the current one. 1580db9299fSJens Axboe * sg_size is then one less than alloc size, since the last 1590db9299fSJens Axboe * element is the chain pointer. 1600db9299fSJens Axboe */ 1617cedb1f1SJames Bottomley if (alloc_size > max_ents) { 1627cedb1f1SJames Bottomley next = sg_chain_ptr(&sgl[max_ents - 1]); 1637cedb1f1SJames Bottomley alloc_size = max_ents; 1640db9299fSJens Axboe sg_size = alloc_size - 1; 1650db9299fSJens Axboe } else { 1660db9299fSJens Axboe sg_size = alloc_size; 1670db9299fSJens Axboe next = NULL; 1680db9299fSJens Axboe } 1690db9299fSJens Axboe 1700db9299fSJens Axboe table->orig_nents -= sg_size; 1710db9299fSJens Axboe free_fn(sgl, alloc_size); 1720db9299fSJens Axboe sgl = next; 1730db9299fSJens Axboe } 1740db9299fSJens Axboe 1750db9299fSJens Axboe table->sgl = NULL; 1760db9299fSJens Axboe } 1770db9299fSJens Axboe EXPORT_SYMBOL(__sg_free_table); 1780db9299fSJens Axboe 1790db9299fSJens Axboe /** 1800db9299fSJens Axboe * sg_free_table - Free a previously allocated sg table 1810db9299fSJens Axboe * @table: The mapped sg table header 1820db9299fSJens Axboe * 1830db9299fSJens Axboe **/ 1840db9299fSJens Axboe void sg_free_table(struct sg_table *table) 1850db9299fSJens Axboe { 1867cedb1f1SJames Bottomley __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); 1870db9299fSJens Axboe } 1880db9299fSJens Axboe EXPORT_SYMBOL(sg_free_table); 1890db9299fSJens Axboe 1900db9299fSJens Axboe /** 1910db9299fSJens Axboe * __sg_alloc_table - Allocate and initialize an sg table with given allocator 1920db9299fSJens Axboe * @table: The sg table header to use 1930db9299fSJens Axboe * @nents: Number of entries in sg list 1947cedb1f1SJames Bottomley * @max_ents: The maximum number of entries the allocator returns per call 1950db9299fSJens Axboe * @gfp_mask: GFP allocation mask 1960db9299fSJens Axboe * @alloc_fn: Allocator to use 1970db9299fSJens Axboe * 1987cedb1f1SJames Bottomley * Description: 1997cedb1f1SJames Bottomley * This function returns a @table @nents long. The allocator is 2007cedb1f1SJames Bottomley * defined to return scatterlist chunks of maximum size @max_ents. 2017cedb1f1SJames Bottomley * Thus if @nents is bigger than @max_ents, the scatterlists will be 2027cedb1f1SJames Bottomley * chained in units of @max_ents. 2037cedb1f1SJames Bottomley * 2040db9299fSJens Axboe * Notes: 2050db9299fSJens Axboe * If this function returns non-0 (eg failure), the caller must call 2060db9299fSJens Axboe * __sg_free_table() to cleanup any leftover allocations. 2070db9299fSJens Axboe * 2080db9299fSJens Axboe **/ 2097cedb1f1SJames Bottomley int __sg_alloc_table(struct sg_table *table, unsigned int nents, 2107cedb1f1SJames Bottomley unsigned int max_ents, gfp_t gfp_mask, 2110db9299fSJens Axboe sg_alloc_fn *alloc_fn) 2120db9299fSJens Axboe { 2130db9299fSJens Axboe struct scatterlist *sg, *prv; 2140db9299fSJens Axboe unsigned int left; 2150db9299fSJens Axboe 2160db9299fSJens Axboe #ifndef ARCH_HAS_SG_CHAIN 2177cedb1f1SJames Bottomley BUG_ON(nents > max_ents); 2180db9299fSJens Axboe #endif 2190db9299fSJens Axboe 2200db9299fSJens Axboe memset(table, 0, sizeof(*table)); 2210db9299fSJens Axboe 2220db9299fSJens Axboe left = nents; 2230db9299fSJens Axboe prv = NULL; 2240db9299fSJens Axboe do { 2250db9299fSJens Axboe unsigned int sg_size, alloc_size = left; 2260db9299fSJens Axboe 2277cedb1f1SJames Bottomley if (alloc_size > max_ents) { 2287cedb1f1SJames Bottomley alloc_size = max_ents; 2290db9299fSJens Axboe sg_size = alloc_size - 1; 2300db9299fSJens Axboe } else 2310db9299fSJens Axboe sg_size = alloc_size; 2320db9299fSJens Axboe 2330db9299fSJens Axboe left -= sg_size; 2340db9299fSJens Axboe 2350db9299fSJens Axboe sg = alloc_fn(alloc_size, gfp_mask); 2360db9299fSJens Axboe if (unlikely(!sg)) 2370db9299fSJens Axboe return -ENOMEM; 2380db9299fSJens Axboe 2390db9299fSJens Axboe sg_init_table(sg, alloc_size); 2400db9299fSJens Axboe table->nents = table->orig_nents += sg_size; 2410db9299fSJens Axboe 2420db9299fSJens Axboe /* 2430db9299fSJens Axboe * If this is the first mapping, assign the sg table header. 2440db9299fSJens Axboe * If this is not the first mapping, chain previous part. 2450db9299fSJens Axboe */ 2460db9299fSJens Axboe if (prv) 2477cedb1f1SJames Bottomley sg_chain(prv, max_ents, sg); 2480db9299fSJens Axboe else 2490db9299fSJens Axboe table->sgl = sg; 2500db9299fSJens Axboe 2510db9299fSJens Axboe /* 2520db9299fSJens Axboe * If no more entries after this one, mark the end 2530db9299fSJens Axboe */ 2540db9299fSJens Axboe if (!left) 2550db9299fSJens Axboe sg_mark_end(&sg[sg_size - 1]); 2560db9299fSJens Axboe 2570db9299fSJens Axboe /* 2580db9299fSJens Axboe * only really needed for mempool backed sg allocations (like 2590db9299fSJens Axboe * SCSI), a possible improvement here would be to pass the 2600db9299fSJens Axboe * table pointer into the allocator and let that clear these 2610db9299fSJens Axboe * flags 2620db9299fSJens Axboe */ 2630db9299fSJens Axboe gfp_mask &= ~__GFP_WAIT; 2640db9299fSJens Axboe gfp_mask |= __GFP_HIGH; 2650db9299fSJens Axboe prv = sg; 2660db9299fSJens Axboe } while (left); 2670db9299fSJens Axboe 2680db9299fSJens Axboe return 0; 2690db9299fSJens Axboe } 2700db9299fSJens Axboe EXPORT_SYMBOL(__sg_alloc_table); 2710db9299fSJens Axboe 2720db9299fSJens Axboe /** 2730db9299fSJens Axboe * sg_alloc_table - Allocate and initialize an sg table 2740db9299fSJens Axboe * @table: The sg table header to use 2750db9299fSJens Axboe * @nents: Number of entries in sg list 2760db9299fSJens Axboe * @gfp_mask: GFP allocation mask 2770db9299fSJens Axboe * 2780db9299fSJens Axboe * Description: 2790db9299fSJens Axboe * Allocate and initialize an sg table. If @nents@ is larger than 2800db9299fSJens Axboe * SG_MAX_SINGLE_ALLOC a chained sg table will be setup. 2810db9299fSJens Axboe * 2820db9299fSJens Axboe **/ 2830db9299fSJens Axboe int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) 2840db9299fSJens Axboe { 2850db9299fSJens Axboe int ret; 2860db9299fSJens Axboe 2877cedb1f1SJames Bottomley ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, 2887cedb1f1SJames Bottomley gfp_mask, sg_kmalloc); 2890db9299fSJens Axboe if (unlikely(ret)) 2907cedb1f1SJames Bottomley __sg_free_table(table, SG_MAX_SINGLE_ALLOC, sg_kfree); 2910db9299fSJens Axboe 2920db9299fSJens Axboe return ret; 2930db9299fSJens Axboe } 2940db9299fSJens Axboe EXPORT_SYMBOL(sg_alloc_table); 295