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)
{
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))
* 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))
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)
git://bbs.cooldavid.org / net-next-2.6.git / blobdiff