/* * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #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" static int btrfs_decompress_bio(struct compressed_bio *cb); static inline int compressed_bio_size(struct btrfs_fs_info *fs_info, unsigned long disk_size) { u16 csum_size = btrfs_super_csum_size(fs_info->super_copy); return sizeof(struct compressed_bio) + (DIV_ROUND_UP(disk_size, fs_info->sectorsize)) * csum_size; } static int check_compressed_csum(struct btrfs_inode *inode, struct compressed_bio *cb, u64 disk_start) { int ret; struct page *page; unsigned long i; char *kaddr; u32 csum; u32 *cb_sum = &cb->sums; if (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); csum = btrfs_csum_data(kaddr, csum, PAGE_SIZE); btrfs_csum_final(csum, (u8 *)&csum); kunmap_atomic(kaddr); if (csum != *cb_sum) { btrfs_print_data_csum_error(inode, 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) { struct compressed_bio *cb = bio->bi_private; struct inode *inode; struct page *page; unsigned long index; unsigned int mirror = btrfs_io_bio(bio)->mirror_num; int ret; if (bio->bi_status) cb->errors = 1; /* if there are more bios still pending for this compressed * extent, just exit */ if (!refcount_dec_and_test(&cb->pending_bios)) goto out; /* * Record the correct mirror_num in cb->orig_bio so that * read-repair can work properly. */ ASSERT(btrfs_io_bio(cb->orig_bio)); btrfs_io_bio(cb->orig_bio)->mirror_num = mirror; cb->mirror_num = mirror; inode = cb->inode; ret = check_compressed_csum(BTRFS_I(inode), cb, (u64)bio->bi_iter.bi_sector << 9); if (ret) goto csum_failed; /* ok, we're the last bio for this extent, lets start * the decompression. */ ret = btrfs_decompress_bio(cb); 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; put_page(page); } /* do io completion on the original bio */ if (cb->errors) { bio_io_error(cb->orig_bio); } else { int i; struct bio_vec *bvec; /* * we have verified the checksum already, set page * checked so the end_io handlers know about it */ ASSERT(!bio_flagged(bio, BIO_CLONED)); bio_for_each_segment_all(bvec, cb->orig_bio, i) SetPageChecked(bvec->bv_page); bio_endio(cb->orig_bio); } /* 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 void end_compressed_writeback(struct inode *inode, const struct compressed_bio *cb) { unsigned long index = cb->start >> PAGE_SHIFT; unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT; struct page *pages[16]; unsigned long nr_pages = end_index - index + 1; int i; int ret; if (cb->errors) mapping_set_error(inode->i_mapping, -EIO); 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++) { if (cb->errors) SetPageError(pages[i]); end_page_writeback(pages[i]); put_page(pages[i]); } nr_pages -= ret; index += ret; } /* the inode may be gone now */ } /* * 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) { struct extent_io_tree *tree; struct compressed_bio *cb = bio->bi_private; struct inode *inode; struct page *page; unsigned long index; if (bio->bi_status) cb->errors = 1; /* if there are more bios still pending for this compressed * extent, just exit */ if (!refcount_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, bio->bi_status ? 0 : 1); cb->compressed_pages[0]->mapping = NULL; end_compressed_writeback(inode, cb); /* 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; put_page(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. */ blk_status_t 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 btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); struct bio *bio = NULL; 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; blk_status_t ret; int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM; WARN_ON(start & ((u64)PAGE_SIZE - 1)); cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS); if (!cb) return BLK_STS_RESOURCE; refcount_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 = fs_info->fs_devices->latest_bdev; bio = btrfs_bio_alloc(bdev, first_byte); bio_set_op_attrs(bio, REQ_OP_WRITE, 0); bio->bi_private = cb; bio->bi_end_io = end_compressed_bio_write; refcount_set(&cb->pending_bios, 1); /* create and submit bios for the compressed pages */ bytes_left = compressed_len; for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) { int submit = 0; page = compressed_pages[pg_index]; page->mapping = inode->i_mapping; if (bio->bi_iter.bi_size) submit = io_tree->ops->merge_bio_hook(page, 0, PAGE_SIZE, bio, 0); page->mapping = NULL; if (submit || bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_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 */ refcount_inc(&cb->pending_bios); ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA); BUG_ON(ret); /* -ENOMEM */ if (!skip_sum) { ret = btrfs_csum_one_bio(inode, bio, start, 1); BUG_ON(ret); /* -ENOMEM */ } ret = btrfs_map_bio(fs_info, bio, 0, 1); if (ret) { bio->bi_status = ret; bio_endio(bio); } bio_put(bio); bio = btrfs_bio_alloc(bdev, first_byte); bio_set_op_attrs(bio, REQ_OP_WRITE, 0); bio->bi_private = cb; bio->bi_end_io = end_compressed_bio_write; bio_add_page(bio, page, PAGE_SIZE, 0); } if (bytes_left < PAGE_SIZE) { btrfs_info(fs_info, "bytes left %lu compress len %lu nr %lu", bytes_left, cb->compressed_len, cb->nr_pages); } bytes_left -= PAGE_SIZE; first_byte += PAGE_SIZE; cond_resched(); } bio_get(bio); ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA); BUG_ON(ret); /* -ENOMEM */ if (!skip_sum) { ret = btrfs_csum_one_bio(inode, bio, start, 1); BUG_ON(ret); /* -ENOMEM */ } ret = btrfs_map_bio(fs_info, bio, 0, 1); if (ret) { bio->bi_status = ret; bio_endio(bio); } bio_put(bio); return 0; } static u64 bio_end_offset(struct bio *bio) { struct bio_vec *last = &bio->bi_io_vec[bio->bi_vcnt - 1]; return page_offset(last->bv_page) + last->bv_len + last->bv_offset; } 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; last_offset = bio_end_offset(cb->orig_bio); 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_SHIFT; while (last_offset < compressed_end) { pg_index = last_offset >> PAGE_SHIFT; if (pg_index > end_index) break; rcu_read_lock(); page = radix_tree_lookup(&mapping->page_tree, pg_index); rcu_read_unlock(); if (page && !radix_tree_exceptional_entry(page)) { misses++; if (misses > 4) break; goto next; } page = __page_cache_alloc(mapping_gfp_constraint(mapping, ~__GFP_FS)); if (!page) break; if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) { put_page(page); goto next; } end = last_offset + PAGE_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); read_lock(&em_tree->lock); em = lookup_extent_mapping(em_tree, last_offset, PAGE_SIZE); read_unlock(&em_tree->lock); if (!em || last_offset < em->start || (last_offset + PAGE_SIZE > extent_map_end(em)) || (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) { free_extent_map(em); unlock_extent(tree, last_offset, end); unlock_page(page); put_page(page); break; } free_extent_map(em); if (page->index == end_index) { char *userpage; size_t zero_offset = isize & (PAGE_SIZE - 1); if (zero_offset) { int zeros; zeros = PAGE_SIZE - zero_offset; userpage = kmap_atomic(page); memset(userpage + zero_offset, 0, zeros); flush_dcache_page(page); kunmap_atomic(userpage); } } ret = bio_add_page(cb->orig_bio, page, PAGE_SIZE, 0); if (ret == PAGE_SIZE) { nr_pages++; put_page(page); } else { unlock_extent(tree, last_offset, end); unlock_page(page); put_page(page); break; } next: last_offset += PAGE_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_iter.bi_sector points to the compressed extent on disk * bio->bi_io_vec points to all of the inode 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 */ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, int mirror_num, unsigned long bio_flags) { struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); struct extent_io_tree *tree; struct extent_map_tree *em_tree; struct compressed_bio *cb; 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_iter.bi_sector << 9; u64 em_len; u64 em_start; struct extent_map *em; blk_status_t ret = BLK_STS_RESOURCE; int faili = 0; 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_SIZE); read_unlock(&em_tree->lock); if (!em) return BLK_STS_IOERR; compressed_len = em->block_len; cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS); if (!cb) goto out; refcount_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 = bio->bi_iter.bi_size; cb->compressed_len = compressed_len; cb->compress_type = extent_compress_type(bio_flags); cb->orig_bio = bio; nr_pages = DIV_ROUND_UP(compressed_len, PAGE_SIZE); cb->compressed_pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS); if (!cb->compressed_pages) goto fail1; bdev = 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]) { faili = pg_index - 1; ret = BLK_STS_RESOURCE; goto fail2; } } faili = nr_pages - 1; 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 */ cb->len = bio->bi_iter.bi_size; comp_bio = btrfs_bio_alloc(bdev, cur_disk_byte); bio_set_op_attrs (comp_bio, REQ_OP_READ, 0); comp_bio->bi_private = cb; comp_bio->bi_end_io = end_compressed_bio_read; refcount_set(&cb->pending_bios, 1); for (pg_index = 0; pg_index < nr_pages; pg_index++) { int submit = 0; page = cb->compressed_pages[pg_index]; page->mapping = inode->i_mapping; page->index = em_start >> PAGE_SHIFT; if (comp_bio->bi_iter.bi_size) submit = tree->ops->merge_bio_hook(page, 0, PAGE_SIZE, comp_bio, 0); page->mapping = NULL; if (submit || bio_add_page(comp_bio, page, PAGE_SIZE, 0) < PAGE_SIZE) { bio_get(comp_bio); ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA); BUG_ON(ret); /* -ENOMEM */ /* * 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 */ refcount_inc(&cb->pending_bios); if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) { ret = btrfs_lookup_bio_sums(inode, comp_bio, sums); BUG_ON(ret); /* -ENOMEM */ } sums += DIV_ROUND_UP(comp_bio->bi_iter.bi_size, fs_info->sectorsize); ret = btrfs_map_bio(fs_info, comp_bio, mirror_num, 0); if (ret) { comp_bio->bi_status = ret; bio_endio(comp_bio); } bio_put(comp_bio); comp_bio = btrfs_bio_alloc(bdev, cur_disk_byte); bio_set_op_attrs(comp_bio, REQ_OP_READ, 0); comp_bio->bi_private = cb; comp_bio->bi_end_io = end_compressed_bio_read; bio_add_page(comp_bio, page, PAGE_SIZE, 0); } cur_disk_byte += PAGE_SIZE; } bio_get(comp_bio); ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA); BUG_ON(ret); /* -ENOMEM */ if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) { ret = btrfs_lookup_bio_sums(inode, comp_bio, sums); BUG_ON(ret); /* -ENOMEM */ } ret = btrfs_map_bio(fs_info, comp_bio, mirror_num, 0); if (ret) { comp_bio->bi_status = ret; bio_endio(comp_bio); } bio_put(comp_bio); return 0; fail2: while (faili >= 0) { __free_page(cb->compressed_pages[faili]); faili--; } kfree(cb->compressed_pages); fail1: kfree(cb); out: free_extent_map(em); return ret; } static struct { struct list_head idle_ws; spinlock_t ws_lock; /* Number of free workspaces */ int free_ws; /* Total number of allocated workspaces */ atomic_t total_ws; /* Waiters for a free workspace */ wait_queue_head_t ws_wait; } btrfs_comp_ws[BTRFS_COMPRESS_TYPES]; static const struct btrfs_compress_op * const btrfs_compress_op[] = { &btrfs_zlib_compress, &btrfs_lzo_compress, }; void __init btrfs_init_compress(void) { int i; for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) { struct list_head *workspace; INIT_LIST_HEAD(&btrfs_comp_ws[i].idle_ws); spin_lock_init(&btrfs_comp_ws[i].ws_lock); atomic_set(&btrfs_comp_ws[i].total_ws, 0); init_waitqueue_head(&btrfs_comp_ws[i].ws_wait); /* * Preallocate one workspace for each compression type so * we can guarantee forward progress in the worst case */ workspace = btrfs_compress_op[i]->alloc_workspace(); if (IS_ERR(workspace)) { pr_warn("BTRFS: cannot preallocate compression workspace, will try later\n"); } else { atomic_set(&btrfs_comp_ws[i].total_ws, 1); btrfs_comp_ws[i].free_ws = 1; list_add(workspace, &btrfs_comp_ws[i].idle_ws); } } } /* * This finds an available workspace or allocates a new one. * If it's not possible to allocate a new one, waits until there's one. * Preallocation makes a forward progress guarantees and we do not return * errors. */ static struct list_head *find_workspace(int type) { struct list_head *workspace; int cpus = num_online_cpus(); int idx = type - 1; unsigned nofs_flag; struct list_head *idle_ws = &btrfs_comp_ws[idx].idle_ws; spinlock_t *ws_lock = &btrfs_comp_ws[idx].ws_lock; atomic_t *total_ws = &btrfs_comp_ws[idx].total_ws; wait_queue_head_t *ws_wait = &btrfs_comp_ws[idx].ws_wait; int *free_ws = &btrfs_comp_ws[idx].free_ws; again: spin_lock(ws_lock); if (!list_empty(idle_ws)) { workspace = idle_ws->next; list_del(workspace); (*free_ws)--; spin_unlock(ws_lock); return workspace; } if (atomic_read(total_ws) > cpus) { DEFINE_WAIT(wait); spin_unlock(ws_lock); prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE); if (atomic_read(total_ws) > cpus && !*free_ws) schedule(); finish_wait(ws_wait, &wait); goto again; } atomic_inc(total_ws); spin_unlock(ws_lock); /* * Allocation helpers call vmalloc that can't use GFP_NOFS, so we have * to turn it off here because we might get called from the restricted * context of btrfs_compress_bio/btrfs_compress_pages */ nofs_flag = memalloc_nofs_save(); workspace = btrfs_compress_op[idx]->alloc_workspace(); memalloc_nofs_restore(nofs_flag); if (IS_ERR(workspace)) { atomic_dec(total_ws); wake_up(ws_wait); /* * Do not return the error but go back to waiting. There's a * workspace preallocated for each type and the compression * time is bounded so we get to a workspace eventually. This * makes our caller's life easier. * * To prevent silent and low-probability deadlocks (when the * initial preallocation fails), check if there are any * workspaces at all. */ if (atomic_read(total_ws) == 0) { static DEFINE_RATELIMIT_STATE(_rs, /* once per minute */ 60 * HZ, /* no burst */ 1); if (__ratelimit(&_rs)) { pr_warn("BTRFS: no compression workspaces, low memory, retrying\n"); } } goto again; } 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_ws = &btrfs_comp_ws[idx].idle_ws; spinlock_t *ws_lock = &btrfs_comp_ws[idx].ws_lock; atomic_t *total_ws = &btrfs_comp_ws[idx].total_ws; wait_queue_head_t *ws_wait = &btrfs_comp_ws[idx].ws_wait; int *free_ws = &btrfs_comp_ws[idx].free_ws; spin_lock(ws_lock); if (*free_ws <= num_online_cpus()) { list_add(workspace, idle_ws); (*free_ws)++; spin_unlock(ws_lock); goto wake; } spin_unlock(ws_lock); btrfs_compress_op[idx]->free_workspace(workspace); atomic_dec(total_ws); wake: /* * Make sure counter is updated before we wake up waiters. */ smp_mb(); if (waitqueue_active(ws_wait)) wake_up(ws_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(&btrfs_comp_ws[i].idle_ws)) { workspace = btrfs_comp_ws[i].idle_ws.next; list_del(workspace); btrfs_compress_op[i]->free_workspace(workspace); atomic_dec(&btrfs_comp_ws[i].total_ws); } } } /* * Given an address space and start and length, compress the bytes into @pages * that are allocated on demand. * * @out_pages is an in/out parameter, holds maximum number of pages to allocate * and returns number of actually allocated pages * * @total_in is used to return the number of bytes actually read. It * may be smaller than the input length 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 an in/out parameter, must be set to the input length and will * be also 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, struct page **pages, unsigned long *out_pages, unsigned long *total_in, unsigned long *total_out) { struct list_head *workspace; int ret; workspace = find_workspace(type); ret = btrfs_compress_op[type-1]->compress_pages(workspace, mapping, start, pages, out_pages, total_in, total_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 * * orig_bio contains the pages from the file that we want to decompress into * * 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. */ static int btrfs_decompress_bio(struct compressed_bio *cb) { struct list_head *workspace; int ret; int type = cb->compress_type; workspace = find_workspace(type); ret = btrfs_compress_op[type - 1]->decompress_bio(workspace, cb); 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); 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(const char *buf, unsigned long buf_start, unsigned long total_out, u64 disk_start, struct bio *bio) { unsigned long buf_offset; unsigned long current_buf_start; unsigned long start_byte; unsigned long prev_start_byte; unsigned long working_bytes = total_out - buf_start; unsigned long bytes; char *kaddr; struct bio_vec bvec = bio_iter_iovec(bio, bio->bi_iter); /* * 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(bvec.bv_page) - 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_t(unsigned long, bvec.bv_len, PAGE_SIZE - buf_offset); bytes = min(bytes, working_bytes); kaddr = kmap_atomic(bvec.bv_page); memcpy(kaddr + bvec.bv_offset, buf + buf_offset, bytes); kunmap_atomic(kaddr); flush_dcache_page(bvec.bv_page); buf_offset += bytes; working_bytes -= bytes; current_buf_start += bytes; /* check if we need to pick another page */ bio_advance(bio, bytes); if (!bio->bi_iter.bi_size) return 0; bvec = bio_iter_iovec(bio, bio->bi_iter); prev_start_byte = start_byte; start_byte = page_offset(bvec.bv_page) - disk_start; /* * We need to make sure we're only adjusting * our offset into compression working buffer when * we're switching pages. Otherwise we can incorrectly * keep copying when we were actually done. */ if (start_byte != prev_start_byte) { /* * 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; } /* * Compression heuristic. * * For now is's a naive and optimistic 'return true', we'll extend the logic to * quickly (compared to direct compression) detect data characteristics * (compressible/uncompressible) to avoid wasting CPU time on uncompressible * data. * * The following types of analysis can be performed: * - detect mostly zero data * - detect data with low "byte set" size (text, etc) * - detect data with low/high "core byte" set * * Return non-zero if the compression should be done, 0 otherwise. */ int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end) { u64 index = start >> PAGE_SHIFT; u64 end_index = end >> PAGE_SHIFT; struct page *page; int ret = 1; while (index <= end_index) { page = find_get_page(inode->i_mapping, index); kmap(page); kunmap(page); put_page(page); index++; } return ret; }