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 */ 98bc3bcc9SPaul Gortmaker #include <linux/export.h> 105a0e3ad6STejun Heo #include <linux/slab.h> 110db9299fSJens Axboe #include <linux/scatterlist.h> 12b1adaf65SFUJITA Tomonori #include <linux/highmem.h> 13b94de9bbSChris Wilson #include <linux/kmemleak.h> 140db9299fSJens Axboe 150db9299fSJens Axboe /** 160db9299fSJens Axboe * sg_next - return the next scatterlist entry in a list 170db9299fSJens Axboe * @sg: The current sg entry 180db9299fSJens Axboe * 190db9299fSJens Axboe * Description: 200db9299fSJens Axboe * Usually the next entry will be @sg@ + 1, but if this sg element is part 210db9299fSJens Axboe * of a chained scatterlist, it could jump to the start of a new 220db9299fSJens Axboe * scatterlist array. 230db9299fSJens Axboe * 240db9299fSJens Axboe **/ 250db9299fSJens Axboe struct scatterlist *sg_next(struct scatterlist *sg) 260db9299fSJens Axboe { 270db9299fSJens Axboe #ifdef CONFIG_DEBUG_SG 280db9299fSJens Axboe BUG_ON(sg->sg_magic != SG_MAGIC); 290db9299fSJens Axboe #endif 300db9299fSJens Axboe if (sg_is_last(sg)) 310db9299fSJens Axboe return NULL; 320db9299fSJens Axboe 330db9299fSJens Axboe sg++; 340db9299fSJens Axboe if (unlikely(sg_is_chain(sg))) 350db9299fSJens Axboe sg = sg_chain_ptr(sg); 360db9299fSJens Axboe 370db9299fSJens Axboe return sg; 380db9299fSJens Axboe } 390db9299fSJens Axboe EXPORT_SYMBOL(sg_next); 400db9299fSJens Axboe 410db9299fSJens Axboe /** 422e484610SMaxim Levitsky * sg_nents - return total count of entries in scatterlist 432e484610SMaxim Levitsky * @sg: The scatterlist 442e484610SMaxim Levitsky * 452e484610SMaxim Levitsky * Description: 462e484610SMaxim Levitsky * Allows to know how many entries are in sg, taking into acount 472e484610SMaxim Levitsky * chaining as well 482e484610SMaxim Levitsky * 492e484610SMaxim Levitsky **/ 502e484610SMaxim Levitsky int sg_nents(struct scatterlist *sg) 512e484610SMaxim Levitsky { 52232f1b51SMaxim Levitsky int nents; 53232f1b51SMaxim Levitsky for (nents = 0; sg; sg = sg_next(sg)) 542e484610SMaxim Levitsky nents++; 552e484610SMaxim Levitsky return nents; 562e484610SMaxim Levitsky } 572e484610SMaxim Levitsky EXPORT_SYMBOL(sg_nents); 582e484610SMaxim Levitsky 59cfaed10dSTom Lendacky /** 60cfaed10dSTom Lendacky * sg_nents_for_len - return total count of entries in scatterlist 61cfaed10dSTom Lendacky * needed to satisfy the supplied length 62cfaed10dSTom Lendacky * @sg: The scatterlist 63cfaed10dSTom Lendacky * @len: The total required length 64cfaed10dSTom Lendacky * 65cfaed10dSTom Lendacky * Description: 66cfaed10dSTom Lendacky * Determines the number of entries in sg that are required to meet 67cfaed10dSTom Lendacky * the supplied length, taking into acount chaining as well 68cfaed10dSTom Lendacky * 69cfaed10dSTom Lendacky * Returns: 70cfaed10dSTom Lendacky * the number of sg entries needed, negative error on failure 71cfaed10dSTom Lendacky * 72cfaed10dSTom Lendacky **/ 73cfaed10dSTom Lendacky int sg_nents_for_len(struct scatterlist *sg, u64 len) 74cfaed10dSTom Lendacky { 75cfaed10dSTom Lendacky int nents; 76cfaed10dSTom Lendacky u64 total; 77cfaed10dSTom Lendacky 78cfaed10dSTom Lendacky if (!len) 79cfaed10dSTom Lendacky return 0; 80cfaed10dSTom Lendacky 81cfaed10dSTom Lendacky for (nents = 0, total = 0; sg; sg = sg_next(sg)) { 82cfaed10dSTom Lendacky nents++; 83cfaed10dSTom Lendacky total += sg->length; 84cfaed10dSTom Lendacky if (total >= len) 85cfaed10dSTom Lendacky return nents; 86cfaed10dSTom Lendacky } 87cfaed10dSTom Lendacky 88cfaed10dSTom Lendacky return -EINVAL; 89cfaed10dSTom Lendacky } 90cfaed10dSTom Lendacky EXPORT_SYMBOL(sg_nents_for_len); 912e484610SMaxim Levitsky 922e484610SMaxim Levitsky /** 930db9299fSJens Axboe * sg_last - return the last scatterlist entry in a list 940db9299fSJens Axboe * @sgl: First entry in the scatterlist 950db9299fSJens Axboe * @nents: Number of entries in the scatterlist 960db9299fSJens Axboe * 970db9299fSJens Axboe * Description: 980db9299fSJens Axboe * Should only be used casually, it (currently) scans the entire list 990db9299fSJens Axboe * to get the last entry. 1000db9299fSJens Axboe * 1010db9299fSJens Axboe * Note that the @sgl@ pointer passed in need not be the first one, 1020db9299fSJens Axboe * the important bit is that @nents@ denotes the number of entries that 1030db9299fSJens Axboe * exist from @sgl@. 1040db9299fSJens Axboe * 1050db9299fSJens Axboe **/ 1060db9299fSJens Axboe struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents) 1070db9299fSJens Axboe { 1080db9299fSJens Axboe struct scatterlist *sg, *ret = NULL; 1090db9299fSJens Axboe unsigned int i; 1100db9299fSJens Axboe 1110db9299fSJens Axboe for_each_sg(sgl, sg, nents, i) 1120db9299fSJens Axboe ret = sg; 1130db9299fSJens Axboe 1140db9299fSJens Axboe #ifdef CONFIG_DEBUG_SG 1150db9299fSJens Axboe BUG_ON(sgl[0].sg_magic != SG_MAGIC); 1160db9299fSJens Axboe BUG_ON(!sg_is_last(ret)); 1170db9299fSJens Axboe #endif 1180db9299fSJens Axboe return ret; 1190db9299fSJens Axboe } 1200db9299fSJens Axboe EXPORT_SYMBOL(sg_last); 1210db9299fSJens Axboe 1220db9299fSJens Axboe /** 1230db9299fSJens Axboe * sg_init_table - Initialize SG table 1240db9299fSJens Axboe * @sgl: The SG table 1250db9299fSJens Axboe * @nents: Number of entries in table 1260db9299fSJens Axboe * 1270db9299fSJens Axboe * Notes: 1280db9299fSJens Axboe * If this is part of a chained sg table, sg_mark_end() should be 1290db9299fSJens Axboe * used only on the last table part. 1300db9299fSJens Axboe * 1310db9299fSJens Axboe **/ 1320db9299fSJens Axboe void sg_init_table(struct scatterlist *sgl, unsigned int nents) 1330db9299fSJens Axboe { 1340db9299fSJens Axboe memset(sgl, 0, sizeof(*sgl) * nents); 1350db9299fSJens Axboe #ifdef CONFIG_DEBUG_SG 1360db9299fSJens Axboe { 1370db9299fSJens Axboe unsigned int i; 1380db9299fSJens Axboe for (i = 0; i < nents; i++) 1390db9299fSJens Axboe sgl[i].sg_magic = SG_MAGIC; 1400db9299fSJens Axboe } 1410db9299fSJens Axboe #endif 1420db9299fSJens Axboe sg_mark_end(&sgl[nents - 1]); 1430db9299fSJens Axboe } 1440db9299fSJens Axboe EXPORT_SYMBOL(sg_init_table); 1450db9299fSJens Axboe 1460db9299fSJens Axboe /** 1470db9299fSJens Axboe * sg_init_one - Initialize a single entry sg list 1480db9299fSJens Axboe * @sg: SG entry 1490db9299fSJens Axboe * @buf: Virtual address for IO 1500db9299fSJens Axboe * @buflen: IO length 1510db9299fSJens Axboe * 1520db9299fSJens Axboe **/ 1530db9299fSJens Axboe void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen) 1540db9299fSJens Axboe { 1550db9299fSJens Axboe sg_init_table(sg, 1); 1560db9299fSJens Axboe sg_set_buf(sg, buf, buflen); 1570db9299fSJens Axboe } 1580db9299fSJens Axboe EXPORT_SYMBOL(sg_init_one); 1590db9299fSJens Axboe 1600db9299fSJens Axboe /* 1610db9299fSJens Axboe * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree 1620db9299fSJens Axboe * helpers. 1630db9299fSJens Axboe */ 1640db9299fSJens Axboe static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask) 1650db9299fSJens Axboe { 166b94de9bbSChris Wilson if (nents == SG_MAX_SINGLE_ALLOC) { 167b94de9bbSChris Wilson /* 168b94de9bbSChris Wilson * Kmemleak doesn't track page allocations as they are not 169b94de9bbSChris Wilson * commonly used (in a raw form) for kernel data structures. 170b94de9bbSChris Wilson * As we chain together a list of pages and then a normal 171b94de9bbSChris Wilson * kmalloc (tracked by kmemleak), in order to for that last 172b94de9bbSChris Wilson * allocation not to become decoupled (and thus a 173b94de9bbSChris Wilson * false-positive) we need to inform kmemleak of all the 174b94de9bbSChris Wilson * intermediate allocations. 175b94de9bbSChris Wilson */ 176b94de9bbSChris Wilson void *ptr = (void *) __get_free_page(gfp_mask); 177b94de9bbSChris Wilson kmemleak_alloc(ptr, PAGE_SIZE, 1, gfp_mask); 178b94de9bbSChris Wilson return ptr; 179b94de9bbSChris Wilson } else 1800db9299fSJens Axboe return kmalloc(nents * sizeof(struct scatterlist), gfp_mask); 1810db9299fSJens Axboe } 1820db9299fSJens Axboe 1830db9299fSJens Axboe static void sg_kfree(struct scatterlist *sg, unsigned int nents) 1840db9299fSJens Axboe { 185b94de9bbSChris Wilson if (nents == SG_MAX_SINGLE_ALLOC) { 186b94de9bbSChris Wilson kmemleak_free(sg); 1870db9299fSJens Axboe free_page((unsigned long) sg); 188b94de9bbSChris Wilson } else 1890db9299fSJens Axboe kfree(sg); 1900db9299fSJens Axboe } 1910db9299fSJens Axboe 1920db9299fSJens Axboe /** 1930db9299fSJens Axboe * __sg_free_table - Free a previously mapped sg table 1940db9299fSJens Axboe * @table: The sg table header to use 1957cedb1f1SJames Bottomley * @max_ents: The maximum number of entries per single scatterlist 196c53c6d6aSChristoph Hellwig * @skip_first_chunk: don't free the (preallocated) first scatterlist chunk 1970db9299fSJens Axboe * @free_fn: Free function 1980db9299fSJens Axboe * 1990db9299fSJens Axboe * Description: 2007cedb1f1SJames Bottomley * Free an sg table previously allocated and setup with 2017cedb1f1SJames Bottomley * __sg_alloc_table(). The @max_ents value must be identical to 2027cedb1f1SJames Bottomley * that previously used with __sg_alloc_table(). 2030db9299fSJens Axboe * 2040db9299fSJens Axboe **/ 2057cedb1f1SJames Bottomley void __sg_free_table(struct sg_table *table, unsigned int max_ents, 206c53c6d6aSChristoph Hellwig bool skip_first_chunk, sg_free_fn *free_fn) 2070db9299fSJens Axboe { 2080db9299fSJens Axboe struct scatterlist *sgl, *next; 2090db9299fSJens Axboe 2100db9299fSJens Axboe if (unlikely(!table->sgl)) 2110db9299fSJens Axboe return; 2120db9299fSJens Axboe 2130db9299fSJens Axboe sgl = table->sgl; 2140db9299fSJens Axboe while (table->orig_nents) { 2150db9299fSJens Axboe unsigned int alloc_size = table->orig_nents; 2160db9299fSJens Axboe unsigned int sg_size; 2170db9299fSJens Axboe 2180db9299fSJens Axboe /* 2197cedb1f1SJames Bottomley * If we have more than max_ents segments left, 2200db9299fSJens Axboe * then assign 'next' to the sg table after the current one. 2210db9299fSJens Axboe * sg_size is then one less than alloc size, since the last 2220db9299fSJens Axboe * element is the chain pointer. 2230db9299fSJens Axboe */ 2247cedb1f1SJames Bottomley if (alloc_size > max_ents) { 2257cedb1f1SJames Bottomley next = sg_chain_ptr(&sgl[max_ents - 1]); 2267cedb1f1SJames Bottomley alloc_size = max_ents; 2270db9299fSJens Axboe sg_size = alloc_size - 1; 2280db9299fSJens Axboe } else { 2290db9299fSJens Axboe sg_size = alloc_size; 2300db9299fSJens Axboe next = NULL; 2310db9299fSJens Axboe } 2320db9299fSJens Axboe 2330db9299fSJens Axboe table->orig_nents -= sg_size; 234c21e59d8STony Battersby if (skip_first_chunk) 235c53c6d6aSChristoph Hellwig skip_first_chunk = false; 236c21e59d8STony Battersby else 237c21e59d8STony Battersby free_fn(sgl, alloc_size); 2380db9299fSJens Axboe sgl = next; 2390db9299fSJens Axboe } 2400db9299fSJens Axboe 2410db9299fSJens Axboe table->sgl = NULL; 2420db9299fSJens Axboe } 2430db9299fSJens Axboe EXPORT_SYMBOL(__sg_free_table); 2440db9299fSJens Axboe 2450db9299fSJens Axboe /** 2460db9299fSJens Axboe * sg_free_table - Free a previously allocated sg table 2470db9299fSJens Axboe * @table: The mapped sg table header 2480db9299fSJens Axboe * 2490db9299fSJens Axboe **/ 2500db9299fSJens Axboe void sg_free_table(struct sg_table *table) 2510db9299fSJens Axboe { 252c53c6d6aSChristoph Hellwig __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree); 2530db9299fSJens Axboe } 2540db9299fSJens Axboe EXPORT_SYMBOL(sg_free_table); 2550db9299fSJens Axboe 2560db9299fSJens Axboe /** 2570db9299fSJens Axboe * __sg_alloc_table - Allocate and initialize an sg table with given allocator 2580db9299fSJens Axboe * @table: The sg table header to use 2590db9299fSJens Axboe * @nents: Number of entries in sg list 2607cedb1f1SJames Bottomley * @max_ents: The maximum number of entries the allocator returns per call 2610db9299fSJens Axboe * @gfp_mask: GFP allocation mask 2620db9299fSJens Axboe * @alloc_fn: Allocator to use 2630db9299fSJens Axboe * 2647cedb1f1SJames Bottomley * Description: 2657cedb1f1SJames Bottomley * This function returns a @table @nents long. The allocator is 2667cedb1f1SJames Bottomley * defined to return scatterlist chunks of maximum size @max_ents. 2677cedb1f1SJames Bottomley * Thus if @nents is bigger than @max_ents, the scatterlists will be 2687cedb1f1SJames Bottomley * chained in units of @max_ents. 2697cedb1f1SJames Bottomley * 2700db9299fSJens Axboe * Notes: 2710db9299fSJens Axboe * If this function returns non-0 (eg failure), the caller must call 2720db9299fSJens Axboe * __sg_free_table() to cleanup any leftover allocations. 2730db9299fSJens Axboe * 2740db9299fSJens Axboe **/ 2757cedb1f1SJames Bottomley int __sg_alloc_table(struct sg_table *table, unsigned int nents, 276c53c6d6aSChristoph Hellwig unsigned int max_ents, struct scatterlist *first_chunk, 277c53c6d6aSChristoph Hellwig gfp_t gfp_mask, sg_alloc_fn *alloc_fn) 2780db9299fSJens Axboe { 2790db9299fSJens Axboe struct scatterlist *sg, *prv; 2800db9299fSJens Axboe unsigned int left; 2810db9299fSJens Axboe 28227daabd9SDan Carpenter memset(table, 0, sizeof(*table)); 28327daabd9SDan Carpenter 28427daabd9SDan Carpenter if (nents == 0) 28527daabd9SDan Carpenter return -EINVAL; 286308c09f1SLaura Abbott #ifndef CONFIG_ARCH_HAS_SG_CHAIN 2876fd59a83SNick Bowler if (WARN_ON_ONCE(nents > max_ents)) 2886fd59a83SNick Bowler return -EINVAL; 2890db9299fSJens Axboe #endif 2900db9299fSJens Axboe 2910db9299fSJens Axboe left = nents; 2920db9299fSJens Axboe prv = NULL; 2930db9299fSJens Axboe do { 2940db9299fSJens Axboe unsigned int sg_size, alloc_size = left; 2950db9299fSJens Axboe 2967cedb1f1SJames Bottomley if (alloc_size > max_ents) { 2977cedb1f1SJames Bottomley alloc_size = max_ents; 2980db9299fSJens Axboe sg_size = alloc_size - 1; 2990db9299fSJens Axboe } else 3000db9299fSJens Axboe sg_size = alloc_size; 3010db9299fSJens Axboe 3020db9299fSJens Axboe left -= sg_size; 3030db9299fSJens Axboe 304c53c6d6aSChristoph Hellwig if (first_chunk) { 305c53c6d6aSChristoph Hellwig sg = first_chunk; 306c53c6d6aSChristoph Hellwig first_chunk = NULL; 307c53c6d6aSChristoph Hellwig } else { 3080db9299fSJens Axboe sg = alloc_fn(alloc_size, gfp_mask); 309c53c6d6aSChristoph Hellwig } 310edce6820SJeffrey Carlyle if (unlikely(!sg)) { 311edce6820SJeffrey Carlyle /* 312edce6820SJeffrey Carlyle * Adjust entry count to reflect that the last 313edce6820SJeffrey Carlyle * entry of the previous table won't be used for 314edce6820SJeffrey Carlyle * linkage. Without this, sg_kfree() may get 315edce6820SJeffrey Carlyle * confused. 316edce6820SJeffrey Carlyle */ 317edce6820SJeffrey Carlyle if (prv) 318edce6820SJeffrey Carlyle table->nents = ++table->orig_nents; 319edce6820SJeffrey Carlyle 3200db9299fSJens Axboe return -ENOMEM; 321edce6820SJeffrey Carlyle } 3220db9299fSJens Axboe 3230db9299fSJens Axboe sg_init_table(sg, alloc_size); 3240db9299fSJens Axboe table->nents = table->orig_nents += sg_size; 3250db9299fSJens Axboe 3260db9299fSJens Axboe /* 3270db9299fSJens Axboe * If this is the first mapping, assign the sg table header. 3280db9299fSJens Axboe * If this is not the first mapping, chain previous part. 3290db9299fSJens Axboe */ 3300db9299fSJens Axboe if (prv) 3317cedb1f1SJames Bottomley sg_chain(prv, max_ents, sg); 3320db9299fSJens Axboe else 3330db9299fSJens Axboe table->sgl = sg; 3340db9299fSJens Axboe 3350db9299fSJens Axboe /* 3360db9299fSJens Axboe * If no more entries after this one, mark the end 3370db9299fSJens Axboe */ 3380db9299fSJens Axboe if (!left) 3390db9299fSJens Axboe sg_mark_end(&sg[sg_size - 1]); 3400db9299fSJens Axboe 3410db9299fSJens Axboe prv = sg; 3420db9299fSJens Axboe } while (left); 3430db9299fSJens Axboe 3440db9299fSJens Axboe return 0; 3450db9299fSJens Axboe } 3460db9299fSJens Axboe EXPORT_SYMBOL(__sg_alloc_table); 3470db9299fSJens Axboe 3480db9299fSJens Axboe /** 3490db9299fSJens Axboe * sg_alloc_table - Allocate and initialize an sg table 3500db9299fSJens Axboe * @table: The sg table header to use 3510db9299fSJens Axboe * @nents: Number of entries in sg list 3520db9299fSJens Axboe * @gfp_mask: GFP allocation mask 3530db9299fSJens Axboe * 3540db9299fSJens Axboe * Description: 3550db9299fSJens Axboe * Allocate and initialize an sg table. If @nents@ is larger than 3560db9299fSJens Axboe * SG_MAX_SINGLE_ALLOC a chained sg table will be setup. 3570db9299fSJens Axboe * 3580db9299fSJens Axboe **/ 3590db9299fSJens Axboe int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask) 3600db9299fSJens Axboe { 3610db9299fSJens Axboe int ret; 3620db9299fSJens Axboe 3637cedb1f1SJames Bottomley ret = __sg_alloc_table(table, nents, SG_MAX_SINGLE_ALLOC, 364c53c6d6aSChristoph Hellwig NULL, gfp_mask, sg_kmalloc); 3650db9299fSJens Axboe if (unlikely(ret)) 366c53c6d6aSChristoph Hellwig __sg_free_table(table, SG_MAX_SINGLE_ALLOC, false, sg_kfree); 3670db9299fSJens Axboe 3680db9299fSJens Axboe return ret; 3690db9299fSJens Axboe } 3700db9299fSJens Axboe EXPORT_SYMBOL(sg_alloc_table); 371b1adaf65SFUJITA Tomonori 372b1adaf65SFUJITA Tomonori /** 373efc42bc9STomasz Stanislawski * sg_alloc_table_from_pages - Allocate and initialize an sg table from 374efc42bc9STomasz Stanislawski * an array of pages 375efc42bc9STomasz Stanislawski * @sgt: The sg table header to use 376efc42bc9STomasz Stanislawski * @pages: Pointer to an array of page pointers 377efc42bc9STomasz Stanislawski * @n_pages: Number of pages in the pages array 378efc42bc9STomasz Stanislawski * @offset: Offset from start of the first page to the start of a buffer 379efc42bc9STomasz Stanislawski * @size: Number of valid bytes in the buffer (after offset) 380efc42bc9STomasz Stanislawski * @gfp_mask: GFP allocation mask 381efc42bc9STomasz Stanislawski * 382efc42bc9STomasz Stanislawski * Description: 383efc42bc9STomasz Stanislawski * Allocate and initialize an sg table from a list of pages. Contiguous 384efc42bc9STomasz Stanislawski * ranges of the pages are squashed into a single scatterlist node. A user 385efc42bc9STomasz Stanislawski * may provide an offset at a start and a size of valid data in a buffer 386efc42bc9STomasz Stanislawski * specified by the page array. The returned sg table is released by 387efc42bc9STomasz Stanislawski * sg_free_table. 388efc42bc9STomasz Stanislawski * 389efc42bc9STomasz Stanislawski * Returns: 390efc42bc9STomasz Stanislawski * 0 on success, negative error on failure 391efc42bc9STomasz Stanislawski */ 392efc42bc9STomasz Stanislawski int sg_alloc_table_from_pages(struct sg_table *sgt, 393efc42bc9STomasz Stanislawski struct page **pages, unsigned int n_pages, 394c4860ad6STvrtko Ursulin unsigned int offset, unsigned long size, 395efc42bc9STomasz Stanislawski gfp_t gfp_mask) 396efc42bc9STomasz Stanislawski { 397c125906bSTvrtko Ursulin const unsigned int max_segment = SCATTERLIST_MAX_SEGMENT; 398c125906bSTvrtko Ursulin unsigned int chunks, cur_page, seg_len, i; 399efc42bc9STomasz Stanislawski int ret; 400efc42bc9STomasz Stanislawski struct scatterlist *s; 401efc42bc9STomasz Stanislawski 402efc42bc9STomasz Stanislawski /* compute number of contiguous chunks */ 403efc42bc9STomasz Stanislawski chunks = 1; 404c125906bSTvrtko Ursulin seg_len = 0; 405c125906bSTvrtko Ursulin for (i = 1; i < n_pages; i++) { 406c125906bSTvrtko Ursulin seg_len += PAGE_SIZE; 407c125906bSTvrtko Ursulin if (seg_len >= max_segment || 408c125906bSTvrtko Ursulin page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1) { 409c125906bSTvrtko Ursulin chunks++; 410c125906bSTvrtko Ursulin seg_len = 0; 411c125906bSTvrtko Ursulin } 412c125906bSTvrtko Ursulin } 413efc42bc9STomasz Stanislawski 414efc42bc9STomasz Stanislawski ret = sg_alloc_table(sgt, chunks, gfp_mask); 415efc42bc9STomasz Stanislawski if (unlikely(ret)) 416efc42bc9STomasz Stanislawski return ret; 417efc42bc9STomasz Stanislawski 418efc42bc9STomasz Stanislawski /* merging chunks and putting them into the scatterlist */ 419efc42bc9STomasz Stanislawski cur_page = 0; 420efc42bc9STomasz Stanislawski for_each_sg(sgt->sgl, s, sgt->orig_nents, i) { 421c125906bSTvrtko Ursulin unsigned int j, chunk_size; 422efc42bc9STomasz Stanislawski 423efc42bc9STomasz Stanislawski /* look for the end of the current chunk */ 424c125906bSTvrtko Ursulin seg_len = 0; 425c125906bSTvrtko Ursulin for (j = cur_page + 1; j < n_pages; j++) { 426c125906bSTvrtko Ursulin seg_len += PAGE_SIZE; 427c125906bSTvrtko Ursulin if (seg_len >= max_segment || 428c125906bSTvrtko Ursulin page_to_pfn(pages[j]) != 429efc42bc9STomasz Stanislawski page_to_pfn(pages[j - 1]) + 1) 430efc42bc9STomasz Stanislawski break; 431c125906bSTvrtko Ursulin } 432efc42bc9STomasz Stanislawski 433efc42bc9STomasz Stanislawski chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset; 434c125906bSTvrtko Ursulin sg_set_page(s, pages[cur_page], 435c125906bSTvrtko Ursulin min_t(unsigned long, size, chunk_size), offset); 436efc42bc9STomasz Stanislawski size -= chunk_size; 437efc42bc9STomasz Stanislawski offset = 0; 438efc42bc9STomasz Stanislawski cur_page = j; 439efc42bc9STomasz Stanislawski } 440efc42bc9STomasz Stanislawski 441efc42bc9STomasz Stanislawski return 0; 442efc42bc9STomasz Stanislawski } 443efc42bc9STomasz Stanislawski EXPORT_SYMBOL(sg_alloc_table_from_pages); 444efc42bc9STomasz Stanislawski 445a321e91bSImre Deak void __sg_page_iter_start(struct sg_page_iter *piter, 446a321e91bSImre Deak struct scatterlist *sglist, unsigned int nents, 447a321e91bSImre Deak unsigned long pgoffset) 448a321e91bSImre Deak { 449a321e91bSImre Deak piter->__pg_advance = 0; 450a321e91bSImre Deak piter->__nents = nents; 451a321e91bSImre Deak 452a321e91bSImre Deak piter->sg = sglist; 453a321e91bSImre Deak piter->sg_pgoffset = pgoffset; 454a321e91bSImre Deak } 455a321e91bSImre Deak EXPORT_SYMBOL(__sg_page_iter_start); 456a321e91bSImre Deak 457a321e91bSImre Deak static int sg_page_count(struct scatterlist *sg) 458a321e91bSImre Deak { 459a321e91bSImre Deak return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT; 460a321e91bSImre Deak } 461a321e91bSImre Deak 462a321e91bSImre Deak bool __sg_page_iter_next(struct sg_page_iter *piter) 463a321e91bSImre Deak { 464a321e91bSImre Deak if (!piter->__nents || !piter->sg) 465a321e91bSImre Deak return false; 466a321e91bSImre Deak 467a321e91bSImre Deak piter->sg_pgoffset += piter->__pg_advance; 468a321e91bSImre Deak piter->__pg_advance = 1; 469a321e91bSImre Deak 470a321e91bSImre Deak while (piter->sg_pgoffset >= sg_page_count(piter->sg)) { 471a321e91bSImre Deak piter->sg_pgoffset -= sg_page_count(piter->sg); 472a321e91bSImre Deak piter->sg = sg_next(piter->sg); 473a321e91bSImre Deak if (!--piter->__nents || !piter->sg) 474a321e91bSImre Deak return false; 475a321e91bSImre Deak } 476a321e91bSImre Deak 477a321e91bSImre Deak return true; 478a321e91bSImre Deak } 479a321e91bSImre Deak EXPORT_SYMBOL(__sg_page_iter_next); 480a321e91bSImre Deak 481efc42bc9STomasz Stanislawski /** 482137d3edbSTejun Heo * sg_miter_start - start mapping iteration over a sg list 483137d3edbSTejun Heo * @miter: sg mapping iter to be started 484137d3edbSTejun Heo * @sgl: sg list to iterate over 485137d3edbSTejun Heo * @nents: number of sg entries 486137d3edbSTejun Heo * 487137d3edbSTejun Heo * Description: 488137d3edbSTejun Heo * Starts mapping iterator @miter. 489137d3edbSTejun Heo * 490137d3edbSTejun Heo * Context: 491137d3edbSTejun Heo * Don't care. 492137d3edbSTejun Heo */ 493137d3edbSTejun Heo void sg_miter_start(struct sg_mapping_iter *miter, struct scatterlist *sgl, 494137d3edbSTejun Heo unsigned int nents, unsigned int flags) 495137d3edbSTejun Heo { 496137d3edbSTejun Heo memset(miter, 0, sizeof(struct sg_mapping_iter)); 497137d3edbSTejun Heo 4984225fc85SImre Deak __sg_page_iter_start(&miter->piter, sgl, nents, 0); 4996de7e356SSebastian Andrzej Siewior WARN_ON(!(flags & (SG_MITER_TO_SG | SG_MITER_FROM_SG))); 500137d3edbSTejun Heo miter->__flags = flags; 501137d3edbSTejun Heo } 502137d3edbSTejun Heo EXPORT_SYMBOL(sg_miter_start); 503137d3edbSTejun Heo 50411052004SAkinobu Mita static bool sg_miter_get_next_page(struct sg_mapping_iter *miter) 50511052004SAkinobu Mita { 50611052004SAkinobu Mita if (!miter->__remaining) { 50711052004SAkinobu Mita struct scatterlist *sg; 50811052004SAkinobu Mita unsigned long pgoffset; 50911052004SAkinobu Mita 51011052004SAkinobu Mita if (!__sg_page_iter_next(&miter->piter)) 51111052004SAkinobu Mita return false; 51211052004SAkinobu Mita 51311052004SAkinobu Mita sg = miter->piter.sg; 51411052004SAkinobu Mita pgoffset = miter->piter.sg_pgoffset; 51511052004SAkinobu Mita 51611052004SAkinobu Mita miter->__offset = pgoffset ? 0 : sg->offset; 51711052004SAkinobu Mita miter->__remaining = sg->offset + sg->length - 51811052004SAkinobu Mita (pgoffset << PAGE_SHIFT) - miter->__offset; 51911052004SAkinobu Mita miter->__remaining = min_t(unsigned long, miter->__remaining, 52011052004SAkinobu Mita PAGE_SIZE - miter->__offset); 52111052004SAkinobu Mita } 52211052004SAkinobu Mita 52311052004SAkinobu Mita return true; 52411052004SAkinobu Mita } 52511052004SAkinobu Mita 526137d3edbSTejun Heo /** 527df642ceaSAkinobu Mita * sg_miter_skip - reposition mapping iterator 528df642ceaSAkinobu Mita * @miter: sg mapping iter to be skipped 529df642ceaSAkinobu Mita * @offset: number of bytes to plus the current location 530df642ceaSAkinobu Mita * 531df642ceaSAkinobu Mita * Description: 532df642ceaSAkinobu Mita * Sets the offset of @miter to its current location plus @offset bytes. 533df642ceaSAkinobu Mita * If mapping iterator @miter has been proceeded by sg_miter_next(), this 534df642ceaSAkinobu Mita * stops @miter. 535df642ceaSAkinobu Mita * 536df642ceaSAkinobu Mita * Context: 537df642ceaSAkinobu Mita * Don't care if @miter is stopped, or not proceeded yet. 538df642ceaSAkinobu Mita * Otherwise, preemption disabled if the SG_MITER_ATOMIC is set. 539df642ceaSAkinobu Mita * 540df642ceaSAkinobu Mita * Returns: 541df642ceaSAkinobu Mita * true if @miter contains the valid mapping. false if end of sg 542df642ceaSAkinobu Mita * list is reached. 543df642ceaSAkinobu Mita */ 5440d6077f8SMing Lei bool sg_miter_skip(struct sg_mapping_iter *miter, off_t offset) 545df642ceaSAkinobu Mita { 546df642ceaSAkinobu Mita sg_miter_stop(miter); 547df642ceaSAkinobu Mita 548df642ceaSAkinobu Mita while (offset) { 549df642ceaSAkinobu Mita off_t consumed; 550df642ceaSAkinobu Mita 551df642ceaSAkinobu Mita if (!sg_miter_get_next_page(miter)) 552df642ceaSAkinobu Mita return false; 553df642ceaSAkinobu Mita 554df642ceaSAkinobu Mita consumed = min_t(off_t, offset, miter->__remaining); 555df642ceaSAkinobu Mita miter->__offset += consumed; 556df642ceaSAkinobu Mita miter->__remaining -= consumed; 557df642ceaSAkinobu Mita offset -= consumed; 558df642ceaSAkinobu Mita } 559df642ceaSAkinobu Mita 560df642ceaSAkinobu Mita return true; 561df642ceaSAkinobu Mita } 5620d6077f8SMing Lei EXPORT_SYMBOL(sg_miter_skip); 563df642ceaSAkinobu Mita 564df642ceaSAkinobu Mita /** 565137d3edbSTejun Heo * sg_miter_next - proceed mapping iterator to the next mapping 566137d3edbSTejun Heo * @miter: sg mapping iter to proceed 567137d3edbSTejun Heo * 568137d3edbSTejun Heo * Description: 5698290e2d2STejun Heo * Proceeds @miter to the next mapping. @miter should have been started 5708290e2d2STejun Heo * using sg_miter_start(). On successful return, @miter->page, 5718290e2d2STejun Heo * @miter->addr and @miter->length point to the current mapping. 572137d3edbSTejun Heo * 573137d3edbSTejun Heo * Context: 5748290e2d2STejun Heo * Preemption disabled if SG_MITER_ATOMIC. Preemption must stay disabled 5758290e2d2STejun Heo * till @miter is stopped. May sleep if !SG_MITER_ATOMIC. 576137d3edbSTejun Heo * 577137d3edbSTejun Heo * Returns: 578137d3edbSTejun Heo * true if @miter contains the next mapping. false if end of sg 579137d3edbSTejun Heo * list is reached. 580137d3edbSTejun Heo */ 581137d3edbSTejun Heo bool sg_miter_next(struct sg_mapping_iter *miter) 582137d3edbSTejun Heo { 583137d3edbSTejun Heo sg_miter_stop(miter); 584137d3edbSTejun Heo 5854225fc85SImre Deak /* 5864225fc85SImre Deak * Get to the next page if necessary. 5874225fc85SImre Deak * __remaining, __offset is adjusted by sg_miter_stop 5884225fc85SImre Deak */ 58911052004SAkinobu Mita if (!sg_miter_get_next_page(miter)) 59023c560a9STejun Heo return false; 5914225fc85SImre Deak 5922db76d7cSImre Deak miter->page = sg_page_iter_page(&miter->piter); 5934225fc85SImre Deak miter->consumed = miter->length = miter->__remaining; 594137d3edbSTejun Heo 595137d3edbSTejun Heo if (miter->__flags & SG_MITER_ATOMIC) 5964225fc85SImre Deak miter->addr = kmap_atomic(miter->page) + miter->__offset; 597137d3edbSTejun Heo else 5984225fc85SImre Deak miter->addr = kmap(miter->page) + miter->__offset; 599137d3edbSTejun Heo 600137d3edbSTejun Heo return true; 601137d3edbSTejun Heo } 602137d3edbSTejun Heo EXPORT_SYMBOL(sg_miter_next); 603137d3edbSTejun Heo 604137d3edbSTejun Heo /** 605137d3edbSTejun Heo * sg_miter_stop - stop mapping iteration 606137d3edbSTejun Heo * @miter: sg mapping iter to be stopped 607137d3edbSTejun Heo * 608137d3edbSTejun Heo * Description: 609137d3edbSTejun Heo * Stops mapping iterator @miter. @miter should have been started 6104ba6a2b2SMasahiro Yamada * using sg_miter_start(). A stopped iteration can be resumed by 6114ba6a2b2SMasahiro Yamada * calling sg_miter_next() on it. This is useful when resources (kmap) 6124ba6a2b2SMasahiro Yamada * need to be released during iteration. 613137d3edbSTejun Heo * 614137d3edbSTejun Heo * Context: 6158290e2d2STejun Heo * Preemption disabled if the SG_MITER_ATOMIC is set. Don't care 6168290e2d2STejun Heo * otherwise. 617137d3edbSTejun Heo */ 618137d3edbSTejun Heo void sg_miter_stop(struct sg_mapping_iter *miter) 619137d3edbSTejun Heo { 620137d3edbSTejun Heo WARN_ON(miter->consumed > miter->length); 621137d3edbSTejun Heo 622137d3edbSTejun Heo /* drop resources from the last iteration */ 623137d3edbSTejun Heo if (miter->addr) { 624137d3edbSTejun Heo miter->__offset += miter->consumed; 6254225fc85SImre Deak miter->__remaining -= miter->consumed; 626137d3edbSTejun Heo 6273d77b50cSMing Lei if ((miter->__flags & SG_MITER_TO_SG) && 6283d77b50cSMing Lei !PageSlab(miter->page)) 6296de7e356SSebastian Andrzej Siewior flush_kernel_dcache_page(miter->page); 6306de7e356SSebastian Andrzej Siewior 631137d3edbSTejun Heo if (miter->__flags & SG_MITER_ATOMIC) { 6328290e2d2STejun Heo WARN_ON_ONCE(preemptible()); 633c3eede8eSCong Wang kunmap_atomic(miter->addr); 634137d3edbSTejun Heo } else 635f652c521SArjan van de Ven kunmap(miter->page); 636137d3edbSTejun Heo 637137d3edbSTejun Heo miter->page = NULL; 638137d3edbSTejun Heo miter->addr = NULL; 639137d3edbSTejun Heo miter->length = 0; 640137d3edbSTejun Heo miter->consumed = 0; 641137d3edbSTejun Heo } 642137d3edbSTejun Heo } 643137d3edbSTejun Heo EXPORT_SYMBOL(sg_miter_stop); 644137d3edbSTejun Heo 645137d3edbSTejun Heo /** 646b1adaf65SFUJITA Tomonori * sg_copy_buffer - Copy data between a linear buffer and an SG list 647b1adaf65SFUJITA Tomonori * @sgl: The SG list 648b1adaf65SFUJITA Tomonori * @nents: Number of SG entries 649b1adaf65SFUJITA Tomonori * @buf: Where to copy from 650b1adaf65SFUJITA Tomonori * @buflen: The number of bytes to copy 651df642ceaSAkinobu Mita * @skip: Number of bytes to skip before copying 652df642ceaSAkinobu Mita * @to_buffer: transfer direction (true == from an sg list to a 653df642ceaSAkinobu Mita * buffer, false == from a buffer to an sg list 654b1adaf65SFUJITA Tomonori * 655b1adaf65SFUJITA Tomonori * Returns the number of copied bytes. 656b1adaf65SFUJITA Tomonori * 657b1adaf65SFUJITA Tomonori **/ 658386ecb12SDave Gordon size_t sg_copy_buffer(struct scatterlist *sgl, unsigned int nents, void *buf, 659386ecb12SDave Gordon size_t buflen, off_t skip, bool to_buffer) 660b1adaf65SFUJITA Tomonori { 661137d3edbSTejun Heo unsigned int offset = 0; 662137d3edbSTejun Heo struct sg_mapping_iter miter; 6636de7e356SSebastian Andrzej Siewior unsigned int sg_flags = SG_MITER_ATOMIC; 664b1adaf65SFUJITA Tomonori 6656de7e356SSebastian Andrzej Siewior if (to_buffer) 6666de7e356SSebastian Andrzej Siewior sg_flags |= SG_MITER_FROM_SG; 6676de7e356SSebastian Andrzej Siewior else 6686de7e356SSebastian Andrzej Siewior sg_flags |= SG_MITER_TO_SG; 6696de7e356SSebastian Andrzej Siewior 6706de7e356SSebastian Andrzej Siewior sg_miter_start(&miter, sgl, nents, sg_flags); 671b1adaf65SFUJITA Tomonori 672df642ceaSAkinobu Mita if (!sg_miter_skip(&miter, skip)) 673df642ceaSAkinobu Mita return false; 674df642ceaSAkinobu Mita 6751d5210efSGilad Ben-Yossef while ((offset < buflen) && sg_miter_next(&miter)) { 676137d3edbSTejun Heo unsigned int len; 677b1adaf65SFUJITA Tomonori 678137d3edbSTejun Heo len = min(miter.length, buflen - offset); 679b1adaf65SFUJITA Tomonori 680b1adaf65SFUJITA Tomonori if (to_buffer) 681137d3edbSTejun Heo memcpy(buf + offset, miter.addr, len); 6826de7e356SSebastian Andrzej Siewior else 683137d3edbSTejun Heo memcpy(miter.addr, buf + offset, len); 684b1adaf65SFUJITA Tomonori 685137d3edbSTejun Heo offset += len; 686b1adaf65SFUJITA Tomonori } 687b1adaf65SFUJITA Tomonori 688137d3edbSTejun Heo sg_miter_stop(&miter); 689b1adaf65SFUJITA Tomonori 690137d3edbSTejun Heo return offset; 691b1adaf65SFUJITA Tomonori } 692386ecb12SDave Gordon EXPORT_SYMBOL(sg_copy_buffer); 693b1adaf65SFUJITA Tomonori 694b1adaf65SFUJITA Tomonori /** 695b1adaf65SFUJITA Tomonori * sg_copy_from_buffer - Copy from a linear buffer to an SG list 696b1adaf65SFUJITA Tomonori * @sgl: The SG list 697b1adaf65SFUJITA Tomonori * @nents: Number of SG entries 698b1adaf65SFUJITA Tomonori * @buf: Where to copy from 699b1adaf65SFUJITA Tomonori * @buflen: The number of bytes to copy 700b1adaf65SFUJITA Tomonori * 701b1adaf65SFUJITA Tomonori * Returns the number of copied bytes. 702b1adaf65SFUJITA Tomonori * 703b1adaf65SFUJITA Tomonori **/ 704b1adaf65SFUJITA Tomonori size_t sg_copy_from_buffer(struct scatterlist *sgl, unsigned int nents, 7052a1bf8f9SDave Gordon const void *buf, size_t buflen) 706b1adaf65SFUJITA Tomonori { 7072a1bf8f9SDave Gordon return sg_copy_buffer(sgl, nents, (void *)buf, buflen, 0, false); 708b1adaf65SFUJITA Tomonori } 709b1adaf65SFUJITA Tomonori EXPORT_SYMBOL(sg_copy_from_buffer); 710b1adaf65SFUJITA Tomonori 711b1adaf65SFUJITA Tomonori /** 712b1adaf65SFUJITA Tomonori * sg_copy_to_buffer - Copy from an SG list to a linear buffer 713b1adaf65SFUJITA Tomonori * @sgl: The SG list 714b1adaf65SFUJITA Tomonori * @nents: Number of SG entries 715b1adaf65SFUJITA Tomonori * @buf: Where to copy to 716b1adaf65SFUJITA Tomonori * @buflen: The number of bytes to copy 717b1adaf65SFUJITA Tomonori * 718b1adaf65SFUJITA Tomonori * Returns the number of copied bytes. 719b1adaf65SFUJITA Tomonori * 720b1adaf65SFUJITA Tomonori **/ 721b1adaf65SFUJITA Tomonori size_t sg_copy_to_buffer(struct scatterlist *sgl, unsigned int nents, 722b1adaf65SFUJITA Tomonori void *buf, size_t buflen) 723b1adaf65SFUJITA Tomonori { 724df642ceaSAkinobu Mita return sg_copy_buffer(sgl, nents, buf, buflen, 0, true); 725b1adaf65SFUJITA Tomonori } 726b1adaf65SFUJITA Tomonori EXPORT_SYMBOL(sg_copy_to_buffer); 727df642ceaSAkinobu Mita 728df642ceaSAkinobu Mita /** 729df642ceaSAkinobu Mita * sg_pcopy_from_buffer - Copy from a linear buffer to an SG list 730df642ceaSAkinobu Mita * @sgl: The SG list 731df642ceaSAkinobu Mita * @nents: Number of SG entries 732df642ceaSAkinobu Mita * @buf: Where to copy from 733df642ceaSAkinobu Mita * @buflen: The number of bytes to copy 7344dc7daf8SDave Gordon * @skip: Number of bytes to skip before copying 735df642ceaSAkinobu Mita * 736df642ceaSAkinobu Mita * Returns the number of copied bytes. 737df642ceaSAkinobu Mita * 738df642ceaSAkinobu Mita **/ 739df642ceaSAkinobu Mita size_t sg_pcopy_from_buffer(struct scatterlist *sgl, unsigned int nents, 7402a1bf8f9SDave Gordon const void *buf, size_t buflen, off_t skip) 741df642ceaSAkinobu Mita { 7422a1bf8f9SDave Gordon return sg_copy_buffer(sgl, nents, (void *)buf, buflen, skip, false); 743df642ceaSAkinobu Mita } 744df642ceaSAkinobu Mita EXPORT_SYMBOL(sg_pcopy_from_buffer); 745df642ceaSAkinobu Mita 746df642ceaSAkinobu Mita /** 747df642ceaSAkinobu Mita * sg_pcopy_to_buffer - Copy from an SG list to a linear buffer 748df642ceaSAkinobu Mita * @sgl: The SG list 749df642ceaSAkinobu Mita * @nents: Number of SG entries 750df642ceaSAkinobu Mita * @buf: Where to copy to 751df642ceaSAkinobu Mita * @buflen: The number of bytes to copy 7524dc7daf8SDave Gordon * @skip: Number of bytes to skip before copying 753df642ceaSAkinobu Mita * 754df642ceaSAkinobu Mita * Returns the number of copied bytes. 755df642ceaSAkinobu Mita * 756df642ceaSAkinobu Mita **/ 757df642ceaSAkinobu Mita size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents, 758df642ceaSAkinobu Mita void *buf, size_t buflen, off_t skip) 759df642ceaSAkinobu Mita { 760df642ceaSAkinobu Mita return sg_copy_buffer(sgl, nents, buf, buflen, skip, true); 761df642ceaSAkinobu Mita } 762df642ceaSAkinobu Mita EXPORT_SYMBOL(sg_pcopy_to_buffer); 7630945e569SJohannes Thumshirn 7640945e569SJohannes Thumshirn /** 7650945e569SJohannes Thumshirn * sg_zero_buffer - Zero-out a part of a SG list 7660945e569SJohannes Thumshirn * @sgl: The SG list 7670945e569SJohannes Thumshirn * @nents: Number of SG entries 7680945e569SJohannes Thumshirn * @buflen: The number of bytes to zero out 7690945e569SJohannes Thumshirn * @skip: Number of bytes to skip before zeroing 7700945e569SJohannes Thumshirn * 7710945e569SJohannes Thumshirn * Returns the number of bytes zeroed. 7720945e569SJohannes Thumshirn **/ 7730945e569SJohannes Thumshirn size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents, 7740945e569SJohannes Thumshirn size_t buflen, off_t skip) 7750945e569SJohannes Thumshirn { 7760945e569SJohannes Thumshirn unsigned int offset = 0; 7770945e569SJohannes Thumshirn struct sg_mapping_iter miter; 7780945e569SJohannes Thumshirn unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG; 7790945e569SJohannes Thumshirn 7800945e569SJohannes Thumshirn sg_miter_start(&miter, sgl, nents, sg_flags); 7810945e569SJohannes Thumshirn 7820945e569SJohannes Thumshirn if (!sg_miter_skip(&miter, skip)) 7830945e569SJohannes Thumshirn return false; 7840945e569SJohannes Thumshirn 7850945e569SJohannes Thumshirn while (offset < buflen && sg_miter_next(&miter)) { 7860945e569SJohannes Thumshirn unsigned int len; 7870945e569SJohannes Thumshirn 7880945e569SJohannes Thumshirn len = min(miter.length, buflen - offset); 7890945e569SJohannes Thumshirn memset(miter.addr, 0, len); 7900945e569SJohannes Thumshirn 7910945e569SJohannes Thumshirn offset += len; 7920945e569SJohannes Thumshirn } 7930945e569SJohannes Thumshirn 7940945e569SJohannes Thumshirn sg_miter_stop(&miter); 7950945e569SJohannes Thumshirn return offset; 7960945e569SJohannes Thumshirn } 7970945e569SJohannes Thumshirn EXPORT_SYMBOL(sg_zero_buffer); 798