Btrfs: Add lowest key information to back refs for extent tree blocks as well.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
parent
7bb86316c3
commit
d8d5f3e16d
|
@ -210,7 +210,7 @@ static int btree_writepages(struct address_space *mapping,
|
||||||
{
|
{
|
||||||
struct extent_map_tree *tree;
|
struct extent_map_tree *tree;
|
||||||
tree = &BTRFS_I(mapping->host)->extent_tree;
|
tree = &BTRFS_I(mapping->host)->extent_tree;
|
||||||
if (0 && wbc->sync_mode == WB_SYNC_NONE) {
|
if (wbc->sync_mode == WB_SYNC_NONE) {
|
||||||
u64 num_dirty;
|
u64 num_dirty;
|
||||||
u64 start = 0;
|
u64 start = 0;
|
||||||
unsigned long thresh = 96 * 1024 * 1024;
|
unsigned long thresh = 96 * 1024 * 1024;
|
||||||
|
|
|
@ -457,6 +457,94 @@ out:
|
||||||
return ret;
|
return ret;
|
||||||
}
|
}
|
||||||
|
|
||||||
|
/*
|
||||||
|
* Back reference rules. Back refs have three main goals:
|
||||||
|
*
|
||||||
|
* 1) differentiate between all holders of references to an extent so that
|
||||||
|
* when a reference is dropped we can make sure it was a valid reference
|
||||||
|
* before freeing the extent.
|
||||||
|
*
|
||||||
|
* 2) Provide enough information to quickly find the holders of an extent
|
||||||
|
* if we notice a given block is corrupted or bad.
|
||||||
|
*
|
||||||
|
* 3) Make it easy to migrate blocks for FS shrinking or storage pool
|
||||||
|
* maintenance. This is actually the same as #2, but with a slightly
|
||||||
|
* different use case.
|
||||||
|
*
|
||||||
|
* File extents can be referenced by:
|
||||||
|
*
|
||||||
|
* - multiple snapshots, subvolumes, or different generations in one subvol
|
||||||
|
* - different files inside a single subvolume (in theory, not implemented yet)
|
||||||
|
* - different offsets inside a file (bookend extents in file.c)
|
||||||
|
*
|
||||||
|
* The extent ref structure has fields for:
|
||||||
|
*
|
||||||
|
* - Objectid of the subvolume root
|
||||||
|
* - Generation number of the tree holding the reference
|
||||||
|
* - objectid of the file holding the reference
|
||||||
|
* - offset in the file corresponding to the key holding the reference
|
||||||
|
*
|
||||||
|
* When a file extent is allocated the fields are filled in:
|
||||||
|
* (root_key.objectid, trans->transid, inode objectid, offset in file)
|
||||||
|
*
|
||||||
|
* When a leaf is cow'd new references are added for every file extent found
|
||||||
|
* in the leaf. It looks the same as the create case, but trans->transid
|
||||||
|
* will be different when the block is cow'd.
|
||||||
|
*
|
||||||
|
* (root_key.objectid, trans->transid, inode objectid, offset in file)
|
||||||
|
*
|
||||||
|
* When a file extent is removed either during snapshot deletion or file
|
||||||
|
* truncation, the corresponding back reference is found
|
||||||
|
* by searching for:
|
||||||
|
*
|
||||||
|
* (btrfs_header_owner(leaf), btrfs_header_generation(leaf),
|
||||||
|
* inode objectid, offset in file)
|
||||||
|
*
|
||||||
|
* Btree extents can be referenced by:
|
||||||
|
*
|
||||||
|
* - Different subvolumes
|
||||||
|
* - Different generations of the same subvolume
|
||||||
|
*
|
||||||
|
* Storing sufficient information for a full reverse mapping of a btree
|
||||||
|
* block would require storing the lowest key of the block in the backref,
|
||||||
|
* and it would require updating that lowest key either before write out or
|
||||||
|
* every time it changed. Instead, the objectid of the lowest key is stored
|
||||||
|
* along with the level of the tree block. This provides a hint
|
||||||
|
* about where in the btree the block can be found. Searches through the
|
||||||
|
* btree only need to look for a pointer to that block, so they stop one
|
||||||
|
* level higher than the level recorded in the backref.
|
||||||
|
*
|
||||||
|
* Some btrees do not do reference counting on their extents. These
|
||||||
|
* include the extent tree and the tree of tree roots. Backrefs for these
|
||||||
|
* trees always have a generation of zero.
|
||||||
|
*
|
||||||
|
* When a tree block is created, back references are inserted:
|
||||||
|
*
|
||||||
|
* (root->root_key.objectid, trans->transid or zero, lowest_key_objectid, level)
|
||||||
|
*
|
||||||
|
* When a tree block is cow'd in a reference counted root,
|
||||||
|
* new back references are added for all the blocks it points to.
|
||||||
|
* These are of the form (trans->transid will have increased since creation):
|
||||||
|
*
|
||||||
|
* (root->root_key.objectid, trans->transid, lowest_key_objectid, level)
|
||||||
|
*
|
||||||
|
* Because the lowest_key_objectid and the level are just hints
|
||||||
|
* they are not used when backrefs are deleted. When a backref is deleted:
|
||||||
|
*
|
||||||
|
* if backref was for a tree root:
|
||||||
|
* root_objectid = root->root_key.objectid
|
||||||
|
* else
|
||||||
|
* root_objectid = btrfs_header_owner(parent)
|
||||||
|
*
|
||||||
|
* (root_objectid, btrfs_header_generation(parent) or zero, 0, 0)
|
||||||
|
*
|
||||||
|
* Back Reference Key hashing:
|
||||||
|
*
|
||||||
|
* Back references have four fields, each 64 bits long. Unfortunately,
|
||||||
|
* This is hashed into a single 64 bit number and placed into the key offset.
|
||||||
|
* The key objectid corresponds to the first byte in the extent, and the
|
||||||
|
* key type is set to BTRFS_EXTENT_REF_KEY
|
||||||
|
*/
|
||||||
int btrfs_insert_extent_backref(struct btrfs_trans_handle *trans,
|
int btrfs_insert_extent_backref(struct btrfs_trans_handle *trans,
|
||||||
struct btrfs_root *root,
|
struct btrfs_root *root,
|
||||||
struct btrfs_path *path, u64 bytenr,
|
struct btrfs_path *path, u64 bytenr,
|
||||||
|
@ -939,10 +1027,13 @@ static int finish_current_insert(struct btrfs_trans_handle *trans, struct
|
||||||
u64 start;
|
u64 start;
|
||||||
u64 end;
|
u64 end;
|
||||||
struct btrfs_fs_info *info = extent_root->fs_info;
|
struct btrfs_fs_info *info = extent_root->fs_info;
|
||||||
|
struct extent_buffer *eb;
|
||||||
struct btrfs_path *path;
|
struct btrfs_path *path;
|
||||||
struct btrfs_key ins;
|
struct btrfs_key ins;
|
||||||
|
struct btrfs_disk_key first;
|
||||||
struct btrfs_extent_item extent_item;
|
struct btrfs_extent_item extent_item;
|
||||||
int ret;
|
int ret;
|
||||||
|
int level;
|
||||||
int err = 0;
|
int err = 0;
|
||||||
|
|
||||||
btrfs_set_stack_extent_refs(&extent_item, 1);
|
btrfs_set_stack_extent_refs(&extent_item, 1);
|
||||||
|
@ -961,10 +1052,19 @@ static int finish_current_insert(struct btrfs_trans_handle *trans, struct
|
||||||
&extent_item, sizeof(extent_item));
|
&extent_item, sizeof(extent_item));
|
||||||
clear_extent_bits(&info->extent_ins, start, end, EXTENT_LOCKED,
|
clear_extent_bits(&info->extent_ins, start, end, EXTENT_LOCKED,
|
||||||
GFP_NOFS);
|
GFP_NOFS);
|
||||||
|
eb = read_tree_block(extent_root, ins.objectid, ins.offset);
|
||||||
|
level = btrfs_header_level(eb);
|
||||||
|
if (level == 0) {
|
||||||
|
btrfs_item_key(eb, &first, 0);
|
||||||
|
} else {
|
||||||
|
btrfs_node_key(eb, &first, 0);
|
||||||
|
}
|
||||||
err = btrfs_insert_extent_backref(trans, extent_root, path,
|
err = btrfs_insert_extent_backref(trans, extent_root, path,
|
||||||
start, extent_root->root_key.objectid,
|
start, extent_root->root_key.objectid,
|
||||||
0, 0, 0);
|
0, btrfs_disk_key_objectid(&first),
|
||||||
|
level);
|
||||||
BUG_ON(err);
|
BUG_ON(err);
|
||||||
|
free_extent_buffer(eb);
|
||||||
}
|
}
|
||||||
btrfs_free_path(path);
|
btrfs_free_path(path);
|
||||||
return 0;
|
return 0;
|
||||||
|
|
|
@ -545,13 +545,10 @@ next_slot:
|
||||||
u64 disk_num_bytes = 0;
|
u64 disk_num_bytes = 0;
|
||||||
u64 extent_num_bytes = 0;
|
u64 extent_num_bytes = 0;
|
||||||
u64 root_gen;
|
u64 root_gen;
|
||||||
|
u64 root_owner;
|
||||||
|
|
||||||
if (leaf != root->node) {
|
|
||||||
root_gen =
|
|
||||||
btrfs_header_generation(path->nodes[1]);
|
|
||||||
} else {
|
|
||||||
root_gen = btrfs_header_generation(leaf);
|
root_gen = btrfs_header_generation(leaf);
|
||||||
}
|
root_owner = btrfs_header_owner(leaf);
|
||||||
if (found_extent) {
|
if (found_extent) {
|
||||||
disk_bytenr =
|
disk_bytenr =
|
||||||
btrfs_file_extent_disk_bytenr(leaf,
|
btrfs_file_extent_disk_bytenr(leaf,
|
||||||
|
@ -575,7 +572,7 @@ next_slot:
|
||||||
ret = btrfs_free_extent(trans, root,
|
ret = btrfs_free_extent(trans, root,
|
||||||
disk_bytenr,
|
disk_bytenr,
|
||||||
disk_num_bytes,
|
disk_num_bytes,
|
||||||
root->root_key.objectid,
|
root_owner,
|
||||||
root_gen, inode->i_ino,
|
root_gen, inode->i_ino,
|
||||||
key.offset, 0);
|
key.offset, 0);
|
||||||
}
|
}
|
||||||
|
|
|
@ -563,6 +563,7 @@ static int btrfs_truncate_in_trans(struct btrfs_trans_handle *trans,
|
||||||
u64 extent_num_bytes = 0;
|
u64 extent_num_bytes = 0;
|
||||||
u64 item_end = 0;
|
u64 item_end = 0;
|
||||||
u64 root_gen = 0;
|
u64 root_gen = 0;
|
||||||
|
u64 root_owner = 0;
|
||||||
int found_extent;
|
int found_extent;
|
||||||
int del_item;
|
int del_item;
|
||||||
int extent_type = -1;
|
int extent_type = -1;
|
||||||
|
@ -673,15 +674,8 @@ static int btrfs_truncate_in_trans(struct btrfs_trans_handle *trans,
|
||||||
found_extent = 1;
|
found_extent = 1;
|
||||||
inode->i_blocks -= num_dec;
|
inode->i_blocks -= num_dec;
|
||||||
}
|
}
|
||||||
if (leaf == root->node) {
|
root_gen = btrfs_header_generation(leaf);
|
||||||
root_gen =
|
root_owner = btrfs_header_owner(leaf);
|
||||||
btrfs_header_generation(leaf);
|
|
||||||
} else {
|
|
||||||
struct extent_buffer *parent;
|
|
||||||
parent = path->nodes[1];
|
|
||||||
root_gen =
|
|
||||||
btrfs_header_generation(parent);
|
|
||||||
}
|
|
||||||
}
|
}
|
||||||
} else if (extent_type == BTRFS_FILE_EXTENT_INLINE &&
|
} else if (extent_type == BTRFS_FILE_EXTENT_INLINE &&
|
||||||
!del_item) {
|
!del_item) {
|
||||||
|
@ -703,7 +697,7 @@ delete:
|
||||||
if (found_extent) {
|
if (found_extent) {
|
||||||
ret = btrfs_free_extent(trans, root, extent_start,
|
ret = btrfs_free_extent(trans, root, extent_start,
|
||||||
extent_num_bytes,
|
extent_num_bytes,
|
||||||
root->root_key.objectid,
|
root_owner,
|
||||||
root_gen, inode->i_ino,
|
root_gen, inode->i_ino,
|
||||||
found_key.offset, 0);
|
found_key.offset, 0);
|
||||||
BUG_ON(ret);
|
BUG_ON(ret);
|
||||||
|
|
Loading…
Reference in a new issue