diff options
Diffstat (limited to 'fs/btrfs/fiemap.c')
| -rw-r--r-- | fs/btrfs/fiemap.c | 929 |
1 files changed, 929 insertions, 0 deletions
diff --git a/fs/btrfs/fiemap.c b/fs/btrfs/fiemap.c new file mode 100644 index 000000000000..43bf0979fd53 --- /dev/null +++ b/fs/btrfs/fiemap.c @@ -0,0 +1,929 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include "backref.h" +#include "btrfs_inode.h" +#include "fiemap.h" +#include "file.h" +#include "file-item.h" + +struct btrfs_fiemap_entry { + u64 offset; + u64 phys; + u64 len; + u32 flags; +}; + +/* + * Indicate the caller of emit_fiemap_extent() that it needs to unlock the file + * range from the inode's io tree, unlock the subvolume tree search path, flush + * the fiemap cache and relock the file range and research the subvolume tree. + * The value here is something negative that can't be confused with a valid + * errno value and different from 1 because that's also a return value from + * fiemap_fill_next_extent() and also it's often used to mean some btree search + * did not find a key, so make it some distinct negative value. + */ +#define BTRFS_FIEMAP_FLUSH_CACHE (-(MAX_ERRNO + 1)) + +/* + * Used to: + * + * - Cache the next entry to be emitted to the fiemap buffer, so that we can + * merge extents that are contiguous and can be grouped as a single one; + * + * - Store extents ready to be written to the fiemap buffer in an intermediary + * buffer. This intermediary buffer is to ensure that in case the fiemap + * buffer is memory mapped to the fiemap target file, we don't deadlock + * during btrfs_page_mkwrite(). This is because during fiemap we are locking + * an extent range in order to prevent races with delalloc flushing and + * ordered extent completion, which is needed in order to reliably detect + * delalloc in holes and prealloc extents. And this can lead to a deadlock + * if the fiemap buffer is memory mapped to the file we are running fiemap + * against (a silly, useless in practice scenario, but possible) because + * btrfs_page_mkwrite() will try to lock the same extent range. + */ +struct fiemap_cache { + /* An array of ready fiemap entries. */ + struct btrfs_fiemap_entry *entries; + /* Number of entries in the entries array. */ + int entries_size; + /* Index of the next entry in the entries array to write to. */ + int entries_pos; + /* + * Once the entries array is full, this indicates what's the offset for + * the next file extent item we must search for in the inode's subvolume + * tree after unlocking the extent range in the inode's io tree and + * releasing the search path. + */ + u64 next_search_offset; + /* + * This matches struct fiemap_extent_info::fi_mapped_extents, we use it + * to count ourselves emitted extents and stop instead of relying on + * fiemap_fill_next_extent() because we buffer ready fiemap entries at + * the @entries array, and we want to stop as soon as we hit the max + * amount of extents to map, not just to save time but also to make the + * logic at extent_fiemap() simpler. + */ + unsigned int extents_mapped; + /* Fields for the cached extent (unsubmitted, not ready, extent). */ + u64 offset; + u64 phys; + u64 len; + u32 flags; + bool cached; +}; + +static int flush_fiemap_cache(struct fiemap_extent_info *fieinfo, + struct fiemap_cache *cache) +{ + for (int i = 0; i < cache->entries_pos; i++) { + struct btrfs_fiemap_entry *entry = &cache->entries[i]; + int ret; + + ret = fiemap_fill_next_extent(fieinfo, entry->offset, + entry->phys, entry->len, + entry->flags); + /* + * Ignore 1 (reached max entries) because we keep track of that + * ourselves in emit_fiemap_extent(). + */ + if (ret < 0) + return ret; + } + cache->entries_pos = 0; + + return 0; +} + +/* + * Helper to submit fiemap extent. + * + * Will try to merge current fiemap extent specified by @offset, @phys, + * @len and @flags with cached one. + * And only when we fails to merge, cached one will be submitted as + * fiemap extent. + * + * Return value is the same as fiemap_fill_next_extent(). + */ +static int emit_fiemap_extent(struct fiemap_extent_info *fieinfo, + struct fiemap_cache *cache, + u64 offset, u64 phys, u64 len, u32 flags) +{ + struct btrfs_fiemap_entry *entry; + u64 cache_end; + + /* Set at the end of extent_fiemap(). */ + ASSERT((flags & FIEMAP_EXTENT_LAST) == 0); + + if (!cache->cached) + goto assign; + + /* + * When iterating the extents of the inode, at extent_fiemap(), we may + * find an extent that starts at an offset behind the end offset of the + * previous extent we processed. This happens if fiemap is called + * without FIEMAP_FLAG_SYNC and there are ordered extents completing + * after we had to unlock the file range, release the search path, emit + * the fiemap extents stored in the buffer (cache->entries array) and + * the lock the remainder of the range and re-search the btree. + * + * For example we are in leaf X processing its last item, which is the + * file extent item for file range [512K, 1M[, and after + * btrfs_next_leaf() releases the path, there's an ordered extent that + * completes for the file range [768K, 2M[, and that results in trimming + * the file extent item so that it now corresponds to the file range + * [512K, 768K[ and a new file extent item is inserted for the file + * range [768K, 2M[, which may end up as the last item of leaf X or as + * the first item of the next leaf - in either case btrfs_next_leaf() + * will leave us with a path pointing to the new extent item, for the + * file range [768K, 2M[, since that's the first key that follows the + * last one we processed. So in order not to report overlapping extents + * to user space, we trim the length of the previously cached extent and + * emit it. + * + * Upon calling btrfs_next_leaf() we may also find an extent with an + * offset smaller than or equals to cache->offset, and this happens + * when we had a hole or prealloc extent with several delalloc ranges in + * it, but after btrfs_next_leaf() released the path, delalloc was + * flushed and the resulting ordered extents were completed, so we can + * now have found a file extent item for an offset that is smaller than + * or equals to what we have in cache->offset. We deal with this as + * described below. + */ + cache_end = cache->offset + cache->len; + if (cache_end > offset) { + if (offset == cache->offset) { + /* + * We cached a dealloc range (found in the io tree) for + * a hole or prealloc extent and we have now found a + * file extent item for the same offset. What we have + * now is more recent and up to date, so discard what + * we had in the cache and use what we have just found. + */ + goto assign; + } else if (offset > cache->offset) { + /* + * The extent range we previously found ends after the + * offset of the file extent item we found and that + * offset falls somewhere in the middle of that previous + * extent range. So adjust the range we previously found + * to end at the offset of the file extent item we have + * just found, since this extent is more up to date. + * Emit that adjusted range and cache the file extent + * item we have just found. This corresponds to the case + * where a previously found file extent item was split + * due to an ordered extent completing. + */ + cache->len = offset - cache->offset; + goto emit; + } else { + const u64 range_end = offset + len; + + /* + * The offset of the file extent item we have just found + * is behind the cached offset. This means we were + * processing a hole or prealloc extent for which we + * have found delalloc ranges (in the io tree), so what + * we have in the cache is the last delalloc range we + * found while the file extent item we found can be + * either for a whole delalloc range we previously + * emitted or only a part of that range. + * + * We have two cases here: + * + * 1) The file extent item's range ends at or behind the + * cached extent's end. In this case just ignore the + * current file extent item because we don't want to + * overlap with previous ranges that may have been + * emitted already; + * + * 2) The file extent item starts behind the currently + * cached extent but its end offset goes beyond the + * end offset of the cached extent. We don't want to + * overlap with a previous range that may have been + * emitted already, so we emit the currently cached + * extent and then partially store the current file + * extent item's range in the cache, for the subrange + * going the cached extent's end to the end of the + * file extent item. + */ + if (range_end <= cache_end) + return 0; + + if (!(flags & (FIEMAP_EXTENT_ENCODED | FIEMAP_EXTENT_DELALLOC))) + phys += cache_end - offset; + + offset = cache_end; + len = range_end - cache_end; + goto emit; + } + } + + /* + * Only merges fiemap extents if + * 1) Their logical addresses are continuous + * + * 2) Their physical addresses are continuous + * So truly compressed (physical size smaller than logical size) + * extents won't get merged with each other + * + * 3) Share same flags + */ + if (cache->offset + cache->len == offset && + cache->phys + cache->len == phys && + cache->flags == flags) { + cache->len += len; + return 0; + } + +emit: + /* Not mergeable, need to submit cached one */ + + if (cache->entries_pos == cache->entries_size) { + /* + * We will need to research for the end offset of the last + * stored extent and not from the current offset, because after + * unlocking the range and releasing the path, if there's a hole + * between that end offset and this current offset, a new extent + * may have been inserted due to a new write, so we don't want + * to miss it. + */ + entry = &cache->entries[cache->entries_size - 1]; + cache->next_search_offset = entry->offset + entry->len; + cache->cached = false; + + return BTRFS_FIEMAP_FLUSH_CACHE; + } + + entry = &cache->entries[cache->entries_pos]; + entry->offset = cache->offset; + entry->phys = cache->phys; + entry->len = cache->len; + entry->flags = cache->flags; + cache->entries_pos++; + cache->extents_mapped++; + + if (cache->extents_mapped == fieinfo->fi_extents_max) { + cache->cached = false; + return 1; + } +assign: + cache->cached = true; + cache->offset = offset; + cache->phys = phys; + cache->len = len; + cache->flags = flags; + + return 0; +} + +/* + * Emit last fiemap cache + * + * The last fiemap cache may still be cached in the following case: + * 0 4k 8k + * |<- Fiemap range ->| + * |<------------ First extent ----------->| + * + * In this case, the first extent range will be cached but not emitted. + * So we must emit it before ending extent_fiemap(). + */ +static int emit_last_fiemap_cache(struct fiemap_extent_info *fieinfo, + struct fiemap_cache *cache) +{ + int ret; + + if (!cache->cached) + return 0; + + ret = fiemap_fill_next_extent(fieinfo, cache->offset, cache->phys, + cache->len, cache->flags); + cache->cached = false; + if (ret > 0) + ret = 0; + return ret; +} + +static int fiemap_next_leaf_item(struct btrfs_inode *inode, struct btrfs_path *path) +{ + struct extent_buffer *clone = path->nodes[0]; + struct btrfs_key key; + int slot; + int ret; + + path->slots[0]++; + if (path->slots[0] < btrfs_header_nritems(path->nodes[0])) + return 0; + + /* + * Add a temporary extra ref to an already cloned extent buffer to + * prevent btrfs_next_leaf() freeing it, we want to reuse it to avoid + * the cost of allocating a new one. + */ + ASSERT(test_bit(EXTENT_BUFFER_UNMAPPED, &clone->bflags)); + atomic_inc(&clone->refs); + + ret = btrfs_next_leaf(inode->root, path); + if (ret != 0) + goto out; + + /* + * Don't bother with cloning if there are no more file extent items for + * our inode. + */ + btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]); + if (key.objectid != btrfs_ino(inode) || key.type != BTRFS_EXTENT_DATA_KEY) { + ret = 1; + goto out; + } + + /* + * Important to preserve the start field, for the optimizations when + * checking if extents are shared (see extent_fiemap()). + * + * We must set ->start before calling copy_extent_buffer_full(). If we + * are on sub-pagesize blocksize, we use ->start to determine the offset + * into the folio where our eb exists, and if we update ->start after + * the fact then any subsequent reads of the eb may read from a + * different offset in the folio than where we originally copied into. + */ + clone->start = path->nodes[0]->start; + /* See the comment at fiemap_search_slot() about why we clone. */ + copy_extent_buffer_full(clone, path->nodes[0]); + + slot = path->slots[0]; + btrfs_release_path(path); + path->nodes[0] = clone; + path->slots[0] = slot; +out: + if (ret) + free_extent_buffer(clone); + + return ret; +} + +/* + * Search for the first file extent item that starts at a given file offset or + * the one that starts immediately before that offset. + * Returns: 0 on success, < 0 on error, 1 if not found. + */ +static int fiemap_search_slot(struct btrfs_inode *inode, struct btrfs_path *path, + u64 file_offset) +{ + const u64 ino = btrfs_ino(inode); + struct btrfs_root *root = inode->root; + struct extent_buffer *clone; + struct btrfs_key key; + int slot; + int ret; + + key.objectid = ino; + key.type = BTRFS_EXTENT_DATA_KEY; + key.offset = file_offset; + + ret = btrfs_search_slot(NULL, root, &key, path, 0, 0); + if (ret < 0) + return ret; + + if (ret > 0 && path->slots[0] > 0) { + btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0] - 1); + if (key.objectid == ino && key.type == BTRFS_EXTENT_DATA_KEY) + path->slots[0]--; + } + + if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) { + ret = btrfs_next_leaf(root, path); + if (ret != 0) + return ret; + + btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]); + if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY) + return 1; + } + + /* + * We clone the leaf and use it during fiemap. This is because while + * using the leaf we do expensive things like checking if an extent is + * shared, which can take a long time. In order to prevent blocking + * other tasks for too long, we use a clone of the leaf. We have locked + * the file range in the inode's io tree, so we know none of our file + * extent items can change. This way we avoid blocking other tasks that + * want to insert items for other inodes in the same leaf or b+tree + * rebalance operations (triggered for example when someone is trying + * to push items into this leaf when trying to insert an item in a + * neighbour leaf). + * We also need the private clone because holding a read lock on an + * extent buffer of the subvolume's b+tree will make lockdep unhappy + * when we check if extents are shared, as backref walking may need to + * lock the same leaf we are processing. + */ + clone = btrfs_clone_extent_buffer(path->nodes[0]); + if (!clone) + return -ENOMEM; + + slot = path->slots[0]; + btrfs_release_path(path); + path->nodes[0] = clone; + path->slots[0] = slot; + + return 0; +} + +/* + * Process a range which is a hole or a prealloc extent in the inode's subvolume + * btree. If @disk_bytenr is 0, we are dealing with a hole, otherwise a prealloc + * extent. The end offset (@end) is inclusive. + */ +static int fiemap_process_hole(struct btrfs_inode *inode, + struct fiemap_extent_info *fieinfo, + struct fiemap_cache *cache, + struct extent_state **delalloc_cached_state, + struct btrfs_backref_share_check_ctx *backref_ctx, + u64 disk_bytenr, u64 extent_offset, + u64 extent_gen, + u64 start, u64 end) +{ + const u64 i_size = i_size_read(&inode->vfs_inode); + u64 cur_offset = start; + u64 last_delalloc_end = 0; + u32 prealloc_flags = FIEMAP_EXTENT_UNWRITTEN; + bool checked_extent_shared = false; + int ret; + + /* + * There can be no delalloc past i_size, so don't waste time looking for + * it beyond i_size. + */ + while (cur_offset < end && cur_offset < i_size) { + u64 delalloc_start; + u64 delalloc_end; + u64 prealloc_start; + u64 prealloc_len = 0; + bool delalloc; + + delalloc = btrfs_find_delalloc_in_range(inode, cur_offset, end, + delalloc_cached_state, + &delalloc_start, + &delalloc_end); + if (!delalloc) + break; + + /* + * If this is a prealloc extent we have to report every section + * of it that has no delalloc. + */ + if (disk_bytenr != 0) { + if (last_delalloc_end == 0) { + prealloc_start = start; + prealloc_len = delalloc_start - start; + } else { + prealloc_start = last_delalloc_end + 1; + prealloc_len = delalloc_start - prealloc_start; + } + } + + if (prealloc_len > 0) { + if (!checked_extent_shared && fieinfo->fi_extents_max) { + ret = btrfs_is_data_extent_shared(inode, + disk_bytenr, + extent_gen, + backref_ctx); + if (ret < 0) + return ret; + else if (ret > 0) + prealloc_flags |= FIEMAP_EXTENT_SHARED; + + checked_extent_shared = true; + } + ret = emit_fiemap_extent(fieinfo, cache, prealloc_start, + disk_bytenr + extent_offset, + prealloc_len, prealloc_flags); + if (ret) + return ret; + extent_offset += prealloc_len; + } + + ret = emit_fiemap_extent(fieinfo, cache, delalloc_start, 0, + delalloc_end + 1 - delalloc_start, + FIEMAP_EXTENT_DELALLOC | + FIEMAP_EXTENT_UNKNOWN); + if (ret) + return ret; + + last_delalloc_end = delalloc_end; + cur_offset = delalloc_end + 1; + extent_offset += cur_offset - delalloc_start; + cond_resched(); + } + + /* + * Either we found no delalloc for the whole prealloc extent or we have + * a prealloc extent that spans i_size or starts at or after i_size. + */ + if (disk_bytenr != 0 && last_delalloc_end < end) { + u64 prealloc_start; + u64 prealloc_len; + + if (last_delalloc_end == 0) { + prealloc_start = start; + prealloc_len = end + 1 - start; + } else { + prealloc_start = last_delalloc_end + 1; + prealloc_len = end + 1 - prealloc_start; + } + + if (!checked_extent_shared && fieinfo->fi_extents_max) { + ret = btrfs_is_data_extent_shared(inode, + disk_bytenr, + extent_gen, + backref_ctx); + if (ret < 0) + return ret; + else if (ret > 0) + prealloc_flags |= FIEMAP_EXTENT_SHARED; + } + ret = emit_fiemap_extent(fieinfo, cache, prealloc_start, + disk_bytenr + extent_offset, + prealloc_len, prealloc_flags); + if (ret) + return ret; + } + + return 0; +} + +static int fiemap_find_last_extent_offset(struct btrfs_inode *inode, + struct btrfs_path *path, + u64 *last_extent_end_ret) +{ + const u64 ino = btrfs_ino(inode); + struct btrfs_root *root = inode->root; + struct extent_buffer *leaf; + struct btrfs_file_extent_item *ei; + struct btrfs_key key; + u64 disk_bytenr; + int ret; + + /* + * Lookup the last file extent. We're not using i_size here because + * there might be preallocation past i_size. + */ + ret = btrfs_lookup_file_extent(NULL, root, path, ino, (u64)-1, 0); + /* There can't be a file extent item at offset (u64)-1 */ + ASSERT(ret != 0); + if (ret < 0) + return ret; + + /* + * For a non-existing key, btrfs_search_slot() always leaves us at a + * slot > 0, except if the btree is empty, which is impossible because + * at least it has the inode item for this inode and all the items for + * the root inode 256. + */ + ASSERT(path->slots[0] > 0); + path->slots[0]--; + leaf = path->nodes[0]; + btrfs_item_key_to_cpu(leaf, &key, path->slots[0]); + if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY) { + /* No file extent items in the subvolume tree. */ + *last_extent_end_ret = 0; + return 0; + } + + /* + * For an inline extent, the disk_bytenr is where inline data starts at, + * so first check if we have an inline extent item before checking if we + * have an implicit hole (disk_bytenr == 0). + */ + ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_file_extent_item); + if (btrfs_file_extent_type(leaf, ei) == BTRFS_FILE_EXTENT_INLINE) { + *last_extent_end_ret = btrfs_file_extent_end(path); + return 0; + } + + /* + * Find the last file extent item that is not a hole (when NO_HOLES is + * not enabled). This should take at most 2 iterations in the worst + * case: we have one hole file extent item at slot 0 of a leaf and + * another hole file extent item as the last item in the previous leaf. + * This is because we merge file extent items that represent holes. + */ + disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, ei); + while (disk_bytenr == 0) { + ret = btrfs_previous_item(root, path, ino, BTRFS_EXTENT_DATA_KEY); + if (ret < 0) { + return ret; + } else if (ret > 0) { + /* No file extent items that are not holes. */ + *last_extent_end_ret = 0; + return 0; + } + leaf = path->nodes[0]; + ei = btrfs_item_ptr(leaf, path->slots[0], + struct btrfs_file_extent_item); + disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, ei); + } + + *last_extent_end_ret = btrfs_file_extent_end(path); + return 0; +} + +static int extent_fiemap(struct btrfs_inode *inode, + struct fiemap_extent_info *fieinfo, + u64 start, u64 len) +{ + const u64 ino = btrfs_ino(inode); + struct extent_state *cached_state = NULL; + struct extent_state *delalloc_cached_state = NULL; + BTRFS_PATH_AUTO_FREE(path); + struct fiemap_cache cache = { 0 }; + struct btrfs_backref_share_check_ctx *backref_ctx; + u64 last_extent_end = 0; + u64 prev_extent_end; + u64 range_start; + u64 range_end; + const u64 sectorsize = inode->root->fs_info->sectorsize; + bool stopped = false; + int ret; + + cache.entries_size = PAGE_SIZE / sizeof(struct btrfs_fiemap_entry); + cache.entries = kmalloc_array(cache.entries_size, + sizeof(struct btrfs_fiemap_entry), + GFP_KERNEL); + backref_ctx = btrfs_alloc_backref_share_check_ctx(); + path = btrfs_alloc_path(); + if (!cache.entries || !backref_ctx || !path) { + ret = -ENOMEM; + goto out; + } + +restart: + range_start = round_down(start, sectorsize); + range_end = round_up(start + len, sectorsize); + prev_extent_end = range_start; + + btrfs_lock_extent(&inode->io_tree, range_start, range_end, &cached_state); + + ret = fiemap_find_last_extent_offset(inode, path, &last_extent_end); + if (ret < 0) + goto out_unlock; + btrfs_release_path(path); + + path->reada = READA_FORWARD; + ret = fiemap_search_slot(inode, path, range_start); + if (ret < 0) { + goto out_unlock; + } else if (ret > 0) { + /* + * No file extent item found, but we may have delalloc between + * the current offset and i_size. So check for that. + */ + ret = 0; + goto check_eof_delalloc; + } + + while (prev_extent_end < range_end) { + struct extent_buffer *leaf = path->nodes[0]; + struct btrfs_file_extent_item *ei; + struct btrfs_key key; + u64 extent_end; + u64 extent_len; + u64 extent_offset = 0; + u64 extent_gen; + u64 disk_bytenr = 0; + u64 flags = 0; + int extent_type; + u8 compression; + + btrfs_item_key_to_cpu(leaf, &key, path->slots[0]); + if (key.objectid != ino || key.type != BTRFS_EXTENT_DATA_KEY) + break; + + extent_end = btrfs_file_extent_end(path); + + /* + * The first iteration can leave us at an extent item that ends + * before our range's start. Move to the next item. + */ + if (extent_end <= range_start) + goto next_item; + + backref_ctx->curr_leaf_bytenr = leaf->start; + + /* We have in implicit hole (NO_HOLES feature enabled). */ + if (prev_extent_end < key.offset) { + const u64 hole_end = min(key.offset, range_end) - 1; + + ret = fiemap_process_hole(inode, fieinfo, &cache, + &delalloc_cached_state, + backref_ctx, 0, 0, 0, + prev_extent_end, hole_end); + if (ret < 0) { + goto out_unlock; + } else if (ret > 0) { + /* fiemap_fill_next_extent() told us to stop. */ + stopped = true; + break; + } + + /* We've reached the end of the fiemap range, stop. */ + if (key.offset >= range_end) { + stopped = true; + break; + } + } + + extent_len = extent_end - key.offset; + ei = btrfs_item_ptr(leaf, path->slots[0], + struct btrfs_file_extent_item); + compression = btrfs_file_extent_compression(leaf, ei); + extent_type = btrfs_file_extent_type(leaf, ei); + extent_gen = btrfs_file_extent_generation(leaf, ei); + + if (extent_type != BTRFS_FILE_EXTENT_INLINE) { + disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, ei); + if (compression == BTRFS_COMPRESS_NONE) + extent_offset = btrfs_file_extent_offset(leaf, ei); + } + + if (compression != BTRFS_COMPRESS_NONE) + flags |= FIEMAP_EXTENT_ENCODED; + + if (extent_type == BTRFS_FILE_EXTENT_INLINE) { + flags |= FIEMAP_EXTENT_DATA_INLINE; + flags |= FIEMAP_EXTENT_NOT_ALIGNED; + ret = emit_fiemap_extent(fieinfo, &cache, key.offset, 0, + extent_len, flags); + } else if (extent_type == BTRFS_FILE_EXTENT_PREALLOC) { + ret = fiemap_process_hole(inode, fieinfo, &cache, + &delalloc_cached_state, + backref_ctx, + disk_bytenr, extent_offset, + extent_gen, key.offset, + extent_end - 1); + } else if (disk_bytenr == 0) { + /* We have an explicit hole. */ + ret = fiemap_process_hole(inode, fieinfo, &cache, + &delalloc_cached_state, + backref_ctx, 0, 0, 0, + key.offset, extent_end - 1); + } else { + /* We have a regular extent. */ + if (fieinfo->fi_extents_max) { + ret = btrfs_is_data_extent_shared(inode, + disk_bytenr, + extent_gen, + backref_ctx); + if (ret < 0) + goto out_unlock; + else if (ret > 0) + flags |= FIEMAP_EXTENT_SHARED; + } + + ret = emit_fiemap_extent(fieinfo, &cache, key.offset, + disk_bytenr + extent_offset, + extent_len, flags); + } + + if (ret < 0) { + goto out_unlock; + } else if (ret > 0) { + /* emit_fiemap_extent() told us to stop. */ + stopped = true; + break; + } + + prev_extent_end = extent_end; +next_item: + if (fatal_signal_pending(current)) { + ret = -EINTR; + goto out_unlock; + } + + ret = fiemap_next_leaf_item(inode, path); + if (ret < 0) { + goto out_unlock; + } else if (ret > 0) { + /* No more file extent items for this inode. */ + break; + } + cond_resched(); + } + +check_eof_delalloc: + if (!stopped && prev_extent_end < range_end) { + ret = fiemap_process_hole(inode, fieinfo, &cache, + &delalloc_cached_state, backref_ctx, + 0, 0, 0, prev_extent_end, range_end - 1); + if (ret < 0) + goto out_unlock; + prev_extent_end = range_end; + } + + if (cache.cached && cache.offset + cache.len >= last_extent_end) { + const u64 i_size = i_size_read(&inode->vfs_inode); + + if (prev_extent_end < i_size) { + u64 delalloc_start; + u64 delalloc_end; + bool delalloc; + + delalloc = btrfs_find_delalloc_in_range(inode, + prev_extent_end, + i_size - 1, + &delalloc_cached_state, + &delalloc_start, + &delalloc_end); + if (!delalloc) + cache.flags |= FIEMAP_EXTENT_LAST; + } else { + cache.flags |= FIEMAP_EXTENT_LAST; + } + } + +out_unlock: + btrfs_unlock_extent(&inode->io_tree, range_start, range_end, &cached_state); + + if (ret == BTRFS_FIEMAP_FLUSH_CACHE) { + btrfs_release_path(path); + ret = flush_fiemap_cache(fieinfo, &cache); + if (ret) + goto out; + len -= cache.next_search_offset - start; + start = cache.next_search_offset; + goto restart; + } else if (ret < 0) { + goto out; + } + + /* + * Must free the path before emitting to the fiemap buffer because we + * may have a non-cloned leaf and if the fiemap buffer is memory mapped + * to a file, a write into it (through btrfs_page_mkwrite()) may trigger + * waiting for an ordered extent that in order to complete needs to + * modify that leaf, therefore leading to a deadlock. + */ + btrfs_free_path(path); + path = NULL; + + ret = flush_fiemap_cache(fieinfo, &cache); + if (ret) + goto out; + + ret = emit_last_fiemap_cache(fieinfo, &cache); +out: + btrfs_free_extent_state(delalloc_cached_state); + kfree(cache.entries); + btrfs_free_backref_share_ctx(backref_ctx); + return ret; +} + +int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, + u64 start, u64 len) +{ + struct btrfs_inode *btrfs_inode = BTRFS_I(inode); + int ret; + + ret = fiemap_prep(inode, fieinfo, start, &len, 0); + if (ret) + return ret; + + /* + * fiemap_prep() called filemap_write_and_wait() for the whole possible + * file range (0 to LLONG_MAX), but that is not enough if we have + * compression enabled. The first filemap_fdatawrite_range() only kicks + * in the compression of data (in an async thread) and will return + * before the compression is done and writeback is started. A second + * filemap_fdatawrite_range() is needed to wait for the compression to + * complete and writeback to start. We also need to wait for ordered + * extents to complete, because our fiemap implementation uses mainly + * file extent items to list the extents, searching for extent maps + * only for file ranges with holes or prealloc extents to figure out + * if we have delalloc in those ranges. + */ + if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC) { + ret = btrfs_wait_ordered_range(btrfs_inode, 0, LLONG_MAX); + if (ret) + return ret; + } + + btrfs_inode_lock(btrfs_inode, BTRFS_ILOCK_SHARED); + + /* + * We did an initial flush to avoid holding the inode's lock while + * triggering writeback and waiting for the completion of IO and ordered + * extents. Now after we locked the inode we do it again, because it's + * possible a new write may have happened in between those two steps. + */ + if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC) { + ret = btrfs_wait_ordered_range(btrfs_inode, 0, LLONG_MAX); + if (ret) { + btrfs_inode_unlock(btrfs_inode, BTRFS_ILOCK_SHARED); + return ret; + } + } + + ret = extent_fiemap(btrfs_inode, fieinfo, start, len); + btrfs_inode_unlock(btrfs_inode, BTRFS_ILOCK_SHARED); + + return ret; +} |