diff options
| -rw-r--r-- | fs/btrfs/inode.c | 156 |
1 files changed, 140 insertions, 16 deletions
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 5d62f21b2e45..5ab120d544bc 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -5255,6 +5255,106 @@ out: return em; } +/* + * returns 1 when the nocow is safe, < 1 on error, 0 if the + * block must be cow'd + */ +static noinline int can_nocow_odirect(struct btrfs_trans_handle *trans, + struct inode *inode, u64 offset, u64 len) +{ + struct btrfs_path *path; + int ret; + struct extent_buffer *leaf; + struct btrfs_root *root = BTRFS_I(inode)->root; + struct btrfs_file_extent_item *fi; + struct btrfs_key key; + u64 disk_bytenr; + u64 backref_offset; + u64 extent_end; + u64 num_bytes; + int slot; + int found_type; + + path = btrfs_alloc_path(); + if (!path) + return -ENOMEM; + + ret = btrfs_lookup_file_extent(trans, root, path, inode->i_ino, + offset, 0); + if (ret < 0) + goto out; + + slot = path->slots[0]; + if (ret == 1) { + if (slot == 0) { + /* can't find the item, must cow */ + ret = 0; + goto out; + } + slot--; + } + ret = 0; + leaf = path->nodes[0]; + btrfs_item_key_to_cpu(leaf, &key, slot); + if (key.objectid != inode->i_ino || + key.type != BTRFS_EXTENT_DATA_KEY) { + /* not our file or wrong item type, must cow */ + goto out; + } + + if (key.offset > offset) { + /* Wrong offset, must cow */ + goto out; + } + + fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item); + found_type = btrfs_file_extent_type(leaf, fi); + if (found_type != BTRFS_FILE_EXTENT_REG && + found_type != BTRFS_FILE_EXTENT_PREALLOC) { + /* not a regular extent, must cow */ + goto out; + } + disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi); + backref_offset = btrfs_file_extent_offset(leaf, fi); + + extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi); + if (extent_end < offset + len) { + /* extent doesn't include our full range, must cow */ + goto out; + } + + if (btrfs_extent_readonly(root, disk_bytenr)) + goto out; + + /* + * look for other files referencing this extent, if we + * find any we must cow + */ + if (btrfs_cross_ref_exist(trans, root, inode->i_ino, + key.offset - backref_offset, disk_bytenr)) + goto out; + + /* + * adjust disk_bytenr and num_bytes to cover just the bytes + * in this extent we are about to write. If there + * are any csums in that range we have to cow in order + * to keep the csums correct + */ + disk_bytenr += backref_offset; + disk_bytenr += offset - key.offset; + num_bytes = min(offset + len, extent_end) - offset; + if (csum_exist_in_range(root, disk_bytenr, num_bytes)) + goto out; + /* + * all of the above have passed, it is safe to overwrite this extent + * without cow + */ + ret = 1; +out: + btrfs_free_path(path); + return ret; +} + static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create) { @@ -5262,6 +5362,7 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock, struct btrfs_root *root = BTRFS_I(inode)->root; u64 start = iblock << inode->i_blkbits; u64 len = bh_result->b_size; + struct btrfs_trans_handle *trans; em = btrfs_get_extent(inode, NULL, 0, start, len, 0); if (IS_ERR(em)) @@ -5306,42 +5407,65 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock, * just use the extent. * */ - if (!create) + if (!create) { + len = em->len - (start - em->start); goto map; + } if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) || ((BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW) && em->block_start != EXTENT_MAP_HOLE)) { - u64 block_start; int type; int ret; + u64 block_start; if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) type = BTRFS_ORDERED_PREALLOC; else type = BTRFS_ORDERED_NOCOW; - len = min(len, em->block_len - (start - em->start)); + len = min(len, em->len - (start - em->start)); block_start = em->block_start + (start - em->start); - ret = btrfs_add_ordered_extent_dio(inode, start, - start, len, len, type); - if (ret) { - free_extent_map(em); - return ret; + + /* + * we're not going to log anything, but we do need + * to make sure the current transaction stays open + * while we look for nocow cross refs + */ + trans = btrfs_join_transaction(root, 0); + if (!trans) + goto must_cow; + + if (can_nocow_odirect(trans, inode, start, len) == 1) { + ret = btrfs_add_ordered_extent_dio(inode, start, + block_start, len, len, type); + btrfs_end_transaction(trans, root); + if (ret) { + free_extent_map(em); + return ret; + } + goto unlock; } - } else { - free_extent_map(em); - em = btrfs_new_extent_direct(inode, start, len); - if (IS_ERR(em)) - return PTR_ERR(em); - len = min(len, em->block_len); + btrfs_end_transaction(trans, root); } +must_cow: + /* + * this will cow the extent, reset the len in case we changed + * it above + */ + len = bh_result->b_size; + free_extent_map(em); + em = btrfs_new_extent_direct(inode, start, len); + if (IS_ERR(em)) + return PTR_ERR(em); + len = min(len, em->len - (start - em->start)); +unlock: clear_extent_bit(&BTRFS_I(inode)->io_tree, start, start + len - 1, EXTENT_LOCKED | EXTENT_DELALLOC | EXTENT_DIRTY, 1, 0, NULL, GFP_NOFS); map: bh_result->b_blocknr = (em->block_start + (start - em->start)) >> inode->i_blkbits; - bh_result->b_size = em->len - (start - em->start); + bh_result->b_size = len; bh_result->b_bdev = em->bdev; set_buffer_mapped(bh_result); if (create && !test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) @@ -5547,7 +5671,7 @@ static void btrfs_submit_direct(int rw, struct bio *bio, struct inode *inode, bvec++; } while (bvec <= (bio->bi_io_vec + bio->bi_vcnt - 1)); - dip->disk_bytenr = bio->bi_sector << 9; + dip->disk_bytenr = (u64)bio->bi_sector << 9; bio->bi_private = dip; if (write) |