/* * Copyright (C) 2008 Oracle. All rights reserved. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public * License v2 as published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public * License along with this program; if not, write to the * Free Software Foundation, Inc., 59 Temple Place - Suite 330, * Boston, MA 021110-1307, USA. */ #include <linux/kernel.h> #include <linux/bio.h> #include <linux/buffer_head.h> #include <linux/file.h> #include <linux/fs.h> #include <linux/pagemap.h> #include <linux/highmem.h> #include <linux/time.h> #include <linux/init.h> #include <linux/string.h> #include <linux/backing-dev.h> #include <linux/mpage.h> #include <linux/swap.h> #include <linux/writeback.h> #include <linux/bit_spinlock.h> #include <linux/slab.h> #include "compat.h" #include "ctree.h" #include "disk-io.h" #include "transaction.h" #include "btrfs_inode.h" #include "volumes.h" #include "ordered-data.h" #include "compression.h" #include "extent_io.h" #include "extent_map.h" struct compressed_bio { /* number of bios pending for this compressed extent */ atomic_t pending_bios; /* the pages with the compressed data on them */ struct page **compressed_pages; /* inode that owns this data */ struct inode *inode; /* starting offset in the inode for our pages */ u64 start; /* number of bytes in the inode we're working on */ unsigned long len; /* number of bytes on disk */ unsigned long compressed_len; /* the compression algorithm for this bio */ int compress_type; /* number of compressed pages in the array */ unsigned long nr_pages; /* IO errors */ int errors; int mirror_num; /* for reads, this is the bio we are copying the data into */ struct bio *orig_bio; /* * the start of a variable length array of checksums only * used by reads */ u32 sums; }; static inline int compressed_bio_size(struct btrfs_root *root, unsigned long disk_size) { u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy); return sizeof(struct compressed_bio) + ((disk_size + root->sectorsize - 1) / root->sectorsize) * csum_size; } static struct bio *compressed_bio_alloc(struct block_device *bdev, u64 first_byte, gfp_t gfp_flags) { int nr_vecs; nr_vecs = bio_get_nr_vecs(bdev); return btrfs_bio_alloc(bdev, first_byte >> 9, nr_vecs, gfp_flags); } static int check_compressed_csum(struct inode *inode, struct compressed_bio *cb, u64 disk_start) { int ret; struct btrfs_root *root = BTRFS_I(inode)->root; struct page *page; unsigned long i; char *kaddr; u32 csum; u32 *cb_sum = &cb->sums; if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM) return 0; for (i = 0; i < cb->nr_pages; i++) { page = cb->compressed_pages[i]; csum = ~(u32)0; kaddr = kmap_atomic(page, KM_USER0); csum = btrfs_csum_data(root, kaddr, csum, PAGE_CACHE_SIZE); btrfs_csum_final(csum, (char *)&csum); kunmap_atomic(kaddr, KM_USER0); if (csum != *cb_sum) { printk(KERN_INFO "btrfs csum failed ino %llu " "extent %llu csum %u " "wanted %u mirror %d\n", (unsigned long long)btrfs_ino(inode), (unsigned long long)disk_start, csum, *cb_sum, cb->mirror_num); ret = -EIO; goto fail; } cb_sum++; } ret = 0; fail: return ret; } /* when we finish reading compressed pages from the disk, we * decompress them and then run the bio end_io routines on the * decompressed pages (in the inode address space). * * This allows the checksumming and other IO error handling routines * to work normally * * The compressed pages are freed here, and it must be run * in process context */ static void end_compressed_bio_read(struct bio *bio, int err) { struct compressed_bio *cb = bio->bi_private; struct inode *inode; struct page *page; unsigned long index; int ret; if (err) cb->errors = 1; /* if there are more bios still pending for this compressed * extent, just exit */ if (!atomic_dec_and_test(&cb->pending_bios)) goto out; inode = cb->inode; ret = check_compressed_csum(inode, cb, (u64)bio->bi_sector << 9); if (ret) goto csum_failed; /* ok, we're the last bio for this extent, lets start * the decompression. */ ret = btrfs_decompress_biovec(cb->compress_type, cb->compressed_pages, cb->start, cb->orig_bio->bi_io_vec, cb->orig_bio->bi_vcnt, cb->compressed_len); csum_failed: if (ret) cb->errors = 1; /* release the compressed pages */ index = 0; for (index = 0; index < cb->nr_pages; index++) { page = cb->compressed_pages[index]; page->mapping = NULL; page_cache_release(page); } /* do io completion on the original bio */ if (cb->errors) { bio_io_error(cb->orig_bio); } else { int bio_index = 0; struct bio_vec *bvec = cb->orig_bio->bi_io_vec; /* * we have verified the checksum already, set page * checked so the end_io handlers know about it */ while (bio_index < cb->orig_bio->bi_vcnt) { SetPageChecked(bvec->bv_page); bvec++; bio_index++; } bio_endio(cb->orig_bio, 0); } /* finally free the cb struct */ kfree(cb->compressed_pages); kfree(cb); out: bio_put(bio); } /* * Clear the writeback bits on all of the file * pages for a compressed write */ static noinline int end_compressed_writeback(struct inode *inode, u64 start, unsigned long ram_size) { unsigned long index = start >> PAGE_CACHE_SHIFT; unsigned long end_index = (start + ram_size - 1) >> PAGE_CACHE_SHIFT; struct page *pages[16]; unsigned long nr_pages = end_index - index + 1; int i; int ret; while (nr_pages > 0) { ret = find_get_pages_contig(inode->i_mapping, index, min_t(unsigned long, nr_pages, ARRAY_SIZE(pages)), pages); if (ret == 0) { nr_pages -= 1; index += 1; continue; } for (i = 0; i < ret; i++) { end_page_writeback(pages[i]); page_cache_release(pages[i]); } nr_pages -= ret; index += ret; } /* the inode may be gone now */ return 0; } /* * do the cleanup once all the compressed pages hit the disk. * This will clear writeback on the file pages and free the compressed * pages. * * This also calls the writeback end hooks for the file pages so that * metadata and checksums can be updated in the file. */ static void end_compressed_bio_write(struct bio *bio, int err) { struct extent_io_tree *tree; struct compressed_bio *cb = bio->bi_private; struct inode *inode; struct page *page; unsigned long index; if (err) cb->errors = 1; /* if there are more bios still pending for this compressed * extent, just exit */ if (!atomic_dec_and_test(&cb->pending_bios)) goto out; /* ok, we're the last bio for this extent, step one is to * call back into the FS and do all the end_io operations */ inode = cb->inode; tree = &BTRFS_I(inode)->io_tree; cb->compressed_pages[0]->mapping = cb->inode->i_mapping; tree->ops->writepage_end_io_hook(cb->compressed_pages[0], cb->start, cb->start + cb->len - 1, NULL, 1); cb->compressed_pages[0]->mapping = NULL; end_compressed_writeback(inode, cb->start, cb->len); /* note, our inode could be gone now */ /* * release the compressed pages, these came from alloc_page and * are not attached to the inode at all */ index = 0; for (index = 0; index < cb->nr_pages; index++) { page = cb->compressed_pages[index]; page->mapping = NULL; page_cache_release(page); } /* finally free the cb struct */ kfree(cb->compressed_pages); kfree(cb); out: bio_put(bio); } /* * worker function to build and submit bios for previously compressed pages. * The corresponding pages in the inode should be marked for writeback * and the compressed pages should have a reference on them for dropping * when the IO is complete. * * This also checksums the file bytes and gets things ready for * the end io hooks. */ int btrfs_submit_compressed_write(struct inode *inode, u64 start, unsigned long len, u64 disk_start, unsigned long compressed_len, struct page **compressed_pages, unsigned long nr_pages) { struct bio *bio = NULL; struct btrfs_root *root = BTRFS_I(inode)->root; struct compressed_bio *cb; unsigned long bytes_left; struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree; int pg_index = 0; struct page *page; u64 first_byte = disk_start; struct block_device *bdev; int ret; int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM; WARN_ON(start & ((u64)PAGE_CACHE_SIZE - 1)); cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS); if (!cb) return -ENOMEM; atomic_set(&cb->pending_bios, 0); cb->errors = 0; cb->inode = inode; cb->start = start; cb->len = len; cb->mirror_num = 0; cb->compressed_pages = compressed_pages; cb->compressed_len = compressed_len; cb->orig_bio = NULL; cb->nr_pages = nr_pages; bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev; bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS); if(!bio) { kfree(cb); return -ENOMEM; } bio->bi_private = cb; bio->bi_end_io = end_compressed_bio_write; atomic_inc(&cb->pending_bios); /* create and submit bios for the compressed pages */ bytes_left = compressed_len; for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) { page = compressed_pages[pg_index]; page->mapping = inode->i_mapping; if (bio->bi_size) ret = io_tree->ops->merge_bio_hook(page, 0, PAGE_CACHE_SIZE, bio, 0); else ret = 0; page->mapping = NULL; if (ret || bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) < PAGE_CACHE_SIZE) { bio_get(bio); /* * inc the count before we submit the bio so * we know the end IO handler won't happen before * we inc the count. Otherwise, the cb might get * freed before we're done setting it up */ atomic_inc(&cb->pending_bios); ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0); BUG_ON(ret); if (!skip_sum) { ret = btrfs_csum_one_bio(root, inode, bio, start, 1); BUG_ON(ret); } ret = btrfs_map_bio(root, WRITE, bio, 0, 1); BUG_ON(ret); bio_put(bio); bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS); bio->bi_private = cb; bio->bi_end_io = end_compressed_bio_write; bio_add_page(bio, page, PAGE_CACHE_SIZE, 0); } if (bytes_left < PAGE_CACHE_SIZE) { printk("bytes left %lu compress len %lu nr %lu\n", bytes_left, cb->compressed_len, cb->nr_pages); } bytes_left -= PAGE_CACHE_SIZE; first_byte += PAGE_CACHE_SIZE; cond_resched(); } bio_get(bio); ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0); BUG_ON(ret); if (!skip_sum) { ret = btrfs_csum_one_bio(root, inode, bio, start, 1); BUG_ON(ret); } ret = btrfs_map_bio(root, WRITE, bio, 0, 1); BUG_ON(ret); bio_put(bio); return 0; } static noinline int add_ra_bio_pages(struct inode *inode, u64 compressed_end, struct compressed_bio *cb) { unsigned long end_index; unsigned long pg_index; u64 last_offset; u64 isize = i_size_read(inode); int ret; struct page *page; unsigned long nr_pages = 0; struct extent_map *em; struct address_space *mapping = inode->i_mapping; struct extent_map_tree *em_tree; struct extent_io_tree *tree; u64 end; int misses = 0; page = cb->orig_bio->bi_io_vec[cb->orig_bio->bi_vcnt - 1].bv_page; last_offset = (page_offset(page) + PAGE_CACHE_SIZE); em_tree = &BTRFS_I(inode)->extent_tree; tree = &BTRFS_I(inode)->io_tree; if (isize == 0) return 0; end_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT; while (last_offset < compressed_end) { pg_index = last_offset >> PAGE_CACHE_SHIFT; if (pg_index > end_index) break; rcu_read_lock(); page = radix_tree_lookup(&mapping->page_tree, pg_index); rcu_read_unlock(); if (page) { misses++; if (misses > 4) break; goto next; } page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS); if (!page) break; if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) { page_cache_release(page); goto next; } end = last_offset + PAGE_CACHE_SIZE - 1; /* * at this point, we have a locked page in the page cache * for these bytes in the file. But, we have to make * sure they map to this compressed extent on disk. */ set_page_extent_mapped(page); lock_extent(tree, last_offset, end, GFP_NOFS); read_lock(&em_tree->lock); em = lookup_extent_mapping(em_tree, last_offset, PAGE_CACHE_SIZE); read_unlock(&em_tree->lock); if (!em || last_offset < em->start || (last_offset + PAGE_CACHE_SIZE > extent_map_end(em)) || (em->block_start >> 9) != cb->orig_bio->bi_sector) { free_extent_map(em); unlock_extent(tree, last_offset, end, GFP_NOFS); unlock_page(page); page_cache_release(page); break; } free_extent_map(em); if (page->index == end_index) { char *userpage; size_t zero_offset = isize & (PAGE_CACHE_SIZE - 1); if (zero_offset) { int zeros; zeros = PAGE_CACHE_SIZE - zero_offset; userpage = kmap_atomic(page, KM_USER0); memset(userpage + zero_offset, 0, zeros); flush_dcache_page(page); kunmap_atomic(userpage, KM_USER0); } } ret = bio_add_page(cb->orig_bio, page, PAGE_CACHE_SIZE, 0); if (ret == PAGE_CACHE_SIZE) { nr_pages++; page_cache_release(page); } else { unlock_extent(tree, last_offset, end, GFP_NOFS); unlock_page(page); page_cache_release(page); break; } next: last_offset += PAGE_CACHE_SIZE; } return 0; } /* * for a compressed read, the bio we get passed has all the inode pages * in it. We don't actually do IO on those pages but allocate new ones * to hold the compressed pages on disk. * * bio->bi_sector points to the compressed extent on disk * bio->bi_io_vec points to all of the inode pages * bio->bi_vcnt is a count of pages * * After the compressed pages are read, we copy the bytes into the * bio we were passed and then call the bio end_io calls */ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, int mirror_num, unsigned long bio_flags) { struct extent_io_tree *tree; struct extent_map_tree *em_tree; struct compressed_bio *cb; struct btrfs_root *root = BTRFS_I(inode)->root; unsigned long uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE; unsigned long compressed_len; unsigned long nr_pages; unsigned long pg_index; struct page *page; struct block_device *bdev; struct bio *comp_bio; u64 cur_disk_byte = (u64)bio->bi_sector << 9; u64 em_len; u64 em_start; struct extent_map *em; int ret = -ENOMEM; u32 *sums; tree = &BTRFS_I(inode)->io_tree; em_tree = &BTRFS_I(inode)->extent_tree; /* we need the actual starting offset of this extent in the file */ read_lock(&em_tree->lock); em = lookup_extent_mapping(em_tree, page_offset(bio->bi_io_vec->bv_page), PAGE_CACHE_SIZE); read_unlock(&em_tree->lock); compressed_len = em->block_len; cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS); if (!cb) goto out; atomic_set(&cb->pending_bios, 0); cb->errors = 0; cb->inode = inode; cb->mirror_num = mirror_num; sums = &cb->sums; cb->start = em->orig_start; em_len = em->len; em_start = em->start; free_extent_map(em); em = NULL; cb->len = uncompressed_len; cb->compressed_len = compressed_len; cb->compress_type = extent_compress_type(bio_flags); cb->orig_bio = bio; nr_pages = (compressed_len + PAGE_CACHE_SIZE - 1) / PAGE_CACHE_SIZE; cb->compressed_pages = kzalloc(sizeof(struct page *) * nr_pages, GFP_NOFS); if (!cb->compressed_pages) goto fail1; bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev; for (pg_index = 0; pg_index < nr_pages; pg_index++) { cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS | __GFP_HIGHMEM); if (!cb->compressed_pages[pg_index]) goto fail2; } cb->nr_pages = nr_pages; add_ra_bio_pages(inode, em_start + em_len, cb); /* include any pages we added in add_ra-bio_pages */ uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE; cb->len = uncompressed_len; comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS); if (!comp_bio) goto fail2; comp_bio->bi_private = cb; comp_bio->bi_end_io = end_compressed_bio_read; atomic_inc(&cb->pending_bios); for (pg_index = 0; pg_index < nr_pages; pg_index++) { page = cb->compressed_pages[pg_index]; page->mapping = inode->i_mapping; page->index = em_start >> PAGE_CACHE_SHIFT; if (comp_bio->bi_size) ret = tree->ops->merge_bio_hook(page, 0, PAGE_CACHE_SIZE, comp_bio, 0); else ret = 0; page->mapping = NULL; if (ret || bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0) < PAGE_CACHE_SIZE) { bio_get(comp_bio); ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0); BUG_ON(ret); /* * inc the count before we submit the bio so * we know the end IO handler won't happen before * we inc the count. Otherwise, the cb might get * freed before we're done setting it up */ atomic_inc(&cb->pending_bios); if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) { ret = btrfs_lookup_bio_sums(root, inode, comp_bio, sums); BUG_ON(ret); } sums += (comp_bio->bi_size + root->sectorsize - 1) / root->sectorsize; ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0); BUG_ON(ret); bio_put(comp_bio); comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS); comp_bio->bi_private = cb; comp_bio->bi_end_io = end_compressed_bio_read; bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0); } cur_disk_byte += PAGE_CACHE_SIZE; } bio_get(comp_bio); ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0); BUG_ON(ret); if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) { ret = btrfs_lookup_bio_sums(root, inode, comp_bio, sums); BUG_ON(ret); } ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0); BUG_ON(ret); bio_put(comp_bio); return 0; fail2: for (pg_index = 0; pg_index < nr_pages; pg_index++) free_page((unsigned long)cb->compressed_pages[pg_index]); kfree(cb->compressed_pages); fail1: kfree(cb); out: free_extent_map(em); return ret; } static struct list_head comp_idle_workspace[BTRFS_COMPRESS_TYPES]; static spinlock_t comp_workspace_lock[BTRFS_COMPRESS_TYPES]; static int comp_num_workspace[BTRFS_COMPRESS_TYPES]; static atomic_t comp_alloc_workspace[BTRFS_COMPRESS_TYPES]; static wait_queue_head_t comp_workspace_wait[BTRFS_COMPRESS_TYPES]; struct btrfs_compress_op *btrfs_compress_op[] = { &btrfs_zlib_compress, &btrfs_lzo_compress, }; int __init btrfs_init_compress(void) { int i; for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) { INIT_LIST_HEAD(&comp_idle_workspace[i]); spin_lock_init(&comp_workspace_lock[i]); atomic_set(&comp_alloc_workspace[i], 0); init_waitqueue_head(&comp_workspace_wait[i]); } return 0; } /* * this finds an available workspace or allocates a new one * ERR_PTR is returned if things go bad. */ static struct list_head *find_workspace(int type) { struct list_head *workspace; int cpus = num_online_cpus(); int idx = type - 1; struct list_head *idle_workspace = &comp_idle_workspace[idx]; spinlock_t *workspace_lock = &comp_workspace_lock[idx]; atomic_t *alloc_workspace = &comp_alloc_workspace[idx]; wait_queue_head_t *workspace_wait = &comp_workspace_wait[idx]; int *num_workspace = &comp_num_workspace[idx]; again: spin_lock(workspace_lock); if (!list_empty(idle_workspace)) { workspace = idle_workspace->next; list_del(workspace); (*num_workspace)--; spin_unlock(workspace_lock); return workspace; } if (atomic_read(alloc_workspace) > cpus) { DEFINE_WAIT(wait); spin_unlock(workspace_lock); prepare_to_wait(workspace_wait, &wait, TASK_UNINTERRUPTIBLE); if (atomic_read(alloc_workspace) > cpus && !*num_workspace) schedule(); finish_wait(workspace_wait, &wait); goto again; } atomic_inc(alloc_workspace); spin_unlock(workspace_lock); workspace = btrfs_compress_op[idx]->alloc_workspace(); if (IS_ERR(workspace)) { atomic_dec(alloc_workspace); wake_up(workspace_wait); } return workspace; } /* * put a workspace struct back on the list or free it if we have enough * idle ones sitting around */ static void free_workspace(int type, struct list_head *workspace) { int idx = type - 1; struct list_head *idle_workspace = &comp_idle_workspace[idx]; spinlock_t *workspace_lock = &comp_workspace_lock[idx]; atomic_t *alloc_workspace = &comp_alloc_workspace[idx]; wait_queue_head_t *workspace_wait = &comp_workspace_wait[idx]; int *num_workspace = &comp_num_workspace[idx]; spin_lock(workspace_lock); if (*num_workspace < num_online_cpus()) { list_add_tail(workspace, idle_workspace); (*num_workspace)++; spin_unlock(workspace_lock); goto wake; } spin_unlock(workspace_lock); btrfs_compress_op[idx]->free_workspace(workspace); atomic_dec(alloc_workspace); wake: if (waitqueue_active(workspace_wait)) wake_up(workspace_wait); } /* * cleanup function for module exit */ static void free_workspaces(void) { struct list_head *workspace; int i; for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) { while (!list_empty(&comp_idle_workspace[i])) { workspace = comp_idle_workspace[i].next; list_del(workspace); btrfs_compress_op[i]->free_workspace(workspace); atomic_dec(&comp_alloc_workspace[i]); } } } /* * given an address space and start/len, compress the bytes. * * pages are allocated to hold the compressed result and stored * in 'pages' * * out_pages is used to return the number of pages allocated. There * may be pages allocated even if we return an error * * total_in is used to return the number of bytes actually read. It * may be smaller then len if we had to exit early because we * ran out of room in the pages array or because we cross the * max_out threshold. * * total_out is used to return the total number of compressed bytes * * max_out tells us the max number of bytes that we're allowed to * stuff into pages */ int btrfs_compress_pages(int type, struct address_space *mapping, u64 start, unsigned long len, struct page **pages, unsigned long nr_dest_pages, unsigned long *out_pages, unsigned long *total_in, unsigned long *total_out, unsigned long max_out) { struct list_head *workspace; int ret; workspace = find_workspace(type); if (IS_ERR(workspace)) return -1; ret = btrfs_compress_op[type-1]->compress_pages(workspace, mapping, start, len, pages, nr_dest_pages, out_pages, total_in, total_out, max_out); free_workspace(type, workspace); return ret; } /* * pages_in is an array of pages with compressed data. * * disk_start is the starting logical offset of this array in the file * * bvec is a bio_vec of pages from the file that we want to decompress into * * vcnt is the count of pages in the biovec * * srclen is the number of bytes in pages_in * * The basic idea is that we have a bio that was created by readpages. * The pages in the bio are for the uncompressed data, and they may not * be contiguous. They all correspond to the range of bytes covered by * the compressed extent. */ int btrfs_decompress_biovec(int type, struct page **pages_in, u64 disk_start, struct bio_vec *bvec, int vcnt, size_t srclen) { struct list_head *workspace; int ret; workspace = find_workspace(type); if (IS_ERR(workspace)) return -ENOMEM; ret = btrfs_compress_op[type-1]->decompress_biovec(workspace, pages_in, disk_start, bvec, vcnt, srclen); free_workspace(type, workspace); return ret; } /* * a less complex decompression routine. Our compressed data fits in a * single page, and we want to read a single page out of it. * start_byte tells us the offset into the compressed data we're interested in */ int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page, unsigned long start_byte, size_t srclen, size_t destlen) { struct list_head *workspace; int ret; workspace = find_workspace(type); if (IS_ERR(workspace)) return -ENOMEM; ret = btrfs_compress_op[type-1]->decompress(workspace, data_in, dest_page, start_byte, srclen, destlen); free_workspace(type, workspace); return ret; } void btrfs_exit_compress(void) { free_workspaces(); } /* * Copy uncompressed data from working buffer to pages. * * buf_start is the byte offset we're of the start of our workspace buffer. * * total_out is the last byte of the buffer */ int btrfs_decompress_buf2page(char *buf, unsigned long buf_start, unsigned long total_out, u64 disk_start, struct bio_vec *bvec, int vcnt, unsigned long *pg_index, unsigned long *pg_offset) { unsigned long buf_offset; unsigned long current_buf_start; unsigned long start_byte; unsigned long working_bytes = total_out - buf_start; unsigned long bytes; char *kaddr; struct page *page_out = bvec[*pg_index].bv_page; /* * start byte is the first byte of the page we're currently * copying into relative to the start of the compressed data. */ start_byte = page_offset(page_out) - disk_start; /* we haven't yet hit data corresponding to this page */ if (total_out <= start_byte) return 1; /* * the start of the data we care about is offset into * the middle of our working buffer */ if (total_out > start_byte && buf_start < start_byte) { buf_offset = start_byte - buf_start; working_bytes -= buf_offset; } else { buf_offset = 0; } current_buf_start = buf_start; /* copy bytes from the working buffer into the pages */ while (working_bytes > 0) { bytes = min(PAGE_CACHE_SIZE - *pg_offset, PAGE_CACHE_SIZE - buf_offset); bytes = min(bytes, working_bytes); kaddr = kmap_atomic(page_out, KM_USER0); memcpy(kaddr + *pg_offset, buf + buf_offset, bytes); kunmap_atomic(kaddr, KM_USER0); flush_dcache_page(page_out); *pg_offset += bytes; buf_offset += bytes; working_bytes -= bytes; current_buf_start += bytes; /* check if we need to pick another page */ if (*pg_offset == PAGE_CACHE_SIZE) { (*pg_index)++; if (*pg_index >= vcnt) return 0; page_out = bvec[*pg_index].bv_page; *pg_offset = 0; start_byte = page_offset(page_out) - disk_start; /* * make sure our new page is covered by this * working buffer */ if (total_out <= start_byte) return 1; /* * the next page in the biovec might not be adjacent * to the last page, but it might still be found * inside this working buffer. bump our offset pointer */ if (total_out > start_byte && current_buf_start < start_byte) { buf_offset = start_byte - buf_start; working_bytes = total_out - start_byte; current_buf_start = buf_start + buf_offset; } } } return 1; }