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Btrfs: break up btrfs_search_slot into smaller pieces
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btrfs_search_slot was doing too many things at once.  This breaks
it up into more reasonable units.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
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Chris Mason committed Apr 3, 2009
1 parent 04018de commit c8c4286
Showing 1 changed file with 131 additions and 90 deletions.
221 changes: 131 additions & 90 deletions fs/btrfs/ctree.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1244,9 +1244,9 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans,
* readahead one full node of leaves, finding things that are close
* to the block in 'slot', and triggering ra on them.
*/
static noinline void reada_for_search(struct btrfs_root *root,
struct btrfs_path *path,
int level, int slot, u64 objectid)
static void reada_for_search(struct btrfs_root *root,
struct btrfs_path *path,
int level, int slot, u64 objectid)
{
struct extent_buffer *node;
struct btrfs_disk_key disk_key;
Expand Down Expand Up @@ -1446,6 +1446,117 @@ noinline void btrfs_unlock_up_safe(struct btrfs_path *path, int level)
}
}

/*
* helper function for btrfs_search_slot. The goal is to find a block
* in cache without setting the path to blocking. If we find the block
* we return zero and the path is unchanged.
*
* If we can't find the block, we set the path blocking and do some
* reada. -EAGAIN is returned and the search must be repeated.
*/
static int
read_block_for_search(struct btrfs_trans_handle *trans,
struct btrfs_root *root, struct btrfs_path *p,
struct extent_buffer **eb_ret, int level, int slot,
struct btrfs_key *key)
{
u64 blocknr;
u64 gen;
u32 blocksize;
struct extent_buffer *b = *eb_ret;
struct extent_buffer *tmp;

blocknr = btrfs_node_blockptr(b, slot);
gen = btrfs_node_ptr_generation(b, slot);
blocksize = btrfs_level_size(root, level - 1);

tmp = btrfs_find_tree_block(root, blocknr, blocksize);
if (tmp && btrfs_buffer_uptodate(tmp, gen)) {
*eb_ret = tmp;
return 0;
}

/*
* reduce lock contention at high levels
* of the btree by dropping locks before
* we read.
*/
btrfs_release_path(NULL, p);
if (tmp)
free_extent_buffer(tmp);
if (p->reada)
reada_for_search(root, p, level, slot, key->objectid);

tmp = read_tree_block(root, blocknr, blocksize, gen);
if (tmp)
free_extent_buffer(tmp);
return -EAGAIN;
}

/*
* helper function for btrfs_search_slot. This does all of the checks
* for node-level blocks and does any balancing required based on
* the ins_len.
*
* If no extra work was required, zero is returned. If we had to
* drop the path, -EAGAIN is returned and btrfs_search_slot must
* start over
*/
static int
setup_nodes_for_search(struct btrfs_trans_handle *trans,
struct btrfs_root *root, struct btrfs_path *p,
struct extent_buffer *b, int level, int ins_len)
{
int ret;
if ((p->search_for_split || ins_len > 0) && btrfs_header_nritems(b) >=
BTRFS_NODEPTRS_PER_BLOCK(root) - 3) {
int sret;

sret = reada_for_balance(root, p, level);
if (sret)
goto again;

btrfs_set_path_blocking(p);
sret = split_node(trans, root, p, level);
btrfs_clear_path_blocking(p, NULL);

BUG_ON(sret > 0);
if (sret) {
ret = sret;
goto done;
}
b = p->nodes[level];
} else if (ins_len < 0 && btrfs_header_nritems(b) <
BTRFS_NODEPTRS_PER_BLOCK(root) / 4) {
int sret;

sret = reada_for_balance(root, p, level);
if (sret)
goto again;

btrfs_set_path_blocking(p);
sret = balance_level(trans, root, p, level);
btrfs_clear_path_blocking(p, NULL);

if (sret) {
ret = sret;
goto done;
}
b = p->nodes[level];
if (!b) {
btrfs_release_path(NULL, p);
goto again;
}
BUG_ON(btrfs_header_nritems(b) == 1);
}
return 0;

again:
ret = -EAGAIN;
done:
return ret;
}

/*
* look for key in the tree. path is filled in with nodes along the way
* if key is found, we return zero and you can find the item in the leaf
Expand All @@ -1464,16 +1575,11 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
ins_len, int cow)
{
struct extent_buffer *b;
struct extent_buffer *tmp;
int slot;
int ret;
int level;
int should_reada = p->reada;
int lowest_unlock = 1;
int blocksize;
u8 lowest_level = 0;
u64 blocknr;
u64 gen;

lowest_level = p->lowest_level;
WARN_ON(lowest_level && ins_len > 0);
Expand Down Expand Up @@ -1502,7 +1608,11 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
if (cow) {
int wret;

/* is a cow on this block not required */
/*
* if we don't really need to cow this block
* then we don't want to set the path blocking,
* so we test it here
*/
if (btrfs_header_generation(b) == trans->transid &&
btrfs_header_owner(b) == root->root_key.objectid &&
!btrfs_header_flag(b, BTRFS_HEADER_FLAG_WRITTEN)) {
Expand Down Expand Up @@ -1557,51 +1667,15 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
if (ret && slot > 0)
slot -= 1;
p->slots[level] = slot;
if ((p->search_for_split || ins_len > 0) &&
btrfs_header_nritems(b) >=
BTRFS_NODEPTRS_PER_BLOCK(root) - 3) {
int sret;

sret = reada_for_balance(root, p, level);
if (sret)
goto again;

btrfs_set_path_blocking(p);
sret = split_node(trans, root, p, level);
btrfs_clear_path_blocking(p, NULL);

BUG_ON(sret > 0);
if (sret) {
ret = sret;
goto done;
}
b = p->nodes[level];
slot = p->slots[level];
} else if (ins_len < 0 &&
btrfs_header_nritems(b) <
BTRFS_NODEPTRS_PER_BLOCK(root) / 4) {
int sret;

sret = reada_for_balance(root, p, level);
if (sret)
goto again;

btrfs_set_path_blocking(p);
sret = balance_level(trans, root, p, level);
btrfs_clear_path_blocking(p, NULL);
ret = setup_nodes_for_search(trans, root, p, b, level,
ins_len);
if (ret == -EAGAIN)
goto again;
else if (ret)
goto done;
b = p->nodes[level];
slot = p->slots[level];

if (sret) {
ret = sret;
goto done;
}
b = p->nodes[level];
if (!b) {
btrfs_release_path(NULL, p);
goto again;
}
slot = p->slots[level];
BUG_ON(btrfs_header_nritems(b) == 1);
}
unlock_up(p, level, lowest_unlock);

/* this is only true while dropping a snapshot */
Expand All @@ -1610,44 +1684,11 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
goto done;
}

blocknr = btrfs_node_blockptr(b, slot);
gen = btrfs_node_ptr_generation(b, slot);
blocksize = btrfs_level_size(root, level - 1);
ret = read_block_for_search(trans, root, p,
&b, level, slot, key);
if (ret == -EAGAIN)
goto again;

tmp = btrfs_find_tree_block(root, blocknr, blocksize);
if (tmp && btrfs_buffer_uptodate(tmp, gen)) {
b = tmp;
} else {
/*
* reduce lock contention at high levels
* of the btree by dropping locks before
* we read.
*/
if (level > 0) {
btrfs_release_path(NULL, p);
if (tmp)
free_extent_buffer(tmp);
if (should_reada)
reada_for_search(root, p,
level, slot,
key->objectid);

tmp = read_tree_block(root, blocknr,
blocksize, gen);
if (tmp)
free_extent_buffer(tmp);
goto again;
} else {
btrfs_set_path_blocking(p);
if (tmp)
free_extent_buffer(tmp);
if (should_reada)
reada_for_search(root, p,
level, slot,
key->objectid);
b = read_node_slot(root, b, slot);
}
}
if (!p->skip_locking) {
int lret;

Expand Down

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