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authorChris Mason <chris.mason@oracle.com>2012-03-19 23:54:38 +0400
committerChris Mason <chris.mason@oracle.com>2012-03-27 01:04:24 +0400
commitf7c79f30cb2d3883488e70cafc9e3a7edd4b9fdb (patch)
tree784c5c878e85a7b8fa283e22767b057d6cfcfa40 /fs
parenta098d8e8eec5a46a47b1bb74390746973d913a9c (diff)
downloadlinux-f7c79f30cb2d3883488e70cafc9e3a7edd4b9fdb.tar.xz
Btrfs: adjust the write_lock_level as we unlock
btrfs_search_slot sometimes needs write locks on high levels of the tree. It remembers the highest level that needs a write lock and will use that for all future searches through the tree in a given call. But, very often we'll just cow the top level or the level below and we won't really need write locks on the root again after that. This patch changes things to adjust the write lock requirement as it unlocks levels. Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/ctree.c23
1 files changed, 17 insertions, 6 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 8af24da983b1..270655da11d1 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1395,7 +1395,8 @@ static noinline int reada_for_balance(struct btrfs_root *root,
* if lowest_unlock is 1, level 0 won't be unlocked
*/
static noinline void unlock_up(struct btrfs_path *path, int level,
- int lowest_unlock)
+ int lowest_unlock, int min_write_lock_level,
+ int *write_lock_level)
{
int i;
int skip_level = level;
@@ -1427,6 +1428,11 @@ static noinline void unlock_up(struct btrfs_path *path, int level,
if (i >= lowest_unlock && i > skip_level && path->locks[i]) {
btrfs_tree_unlock_rw(t, path->locks[i]);
path->locks[i] = 0;
+ if (write_lock_level &&
+ i > min_write_lock_level &&
+ i <= *write_lock_level) {
+ *write_lock_level = i - 1;
+ }
}
}
}
@@ -1650,6 +1656,7 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
/* everything at write_lock_level or lower must be write locked */
int write_lock_level = 0;
u8 lowest_level = 0;
+ int min_write_lock_level;
lowest_level = p->lowest_level;
WARN_ON(lowest_level && ins_len > 0);
@@ -1677,6 +1684,8 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
if (cow && (p->keep_locks || p->lowest_level))
write_lock_level = BTRFS_MAX_LEVEL;
+ min_write_lock_level = write_lock_level;
+
again:
/*
* we try very hard to do read locks on the root
@@ -1808,7 +1817,8 @@ cow_done:
goto again;
}
- unlock_up(p, level, lowest_unlock);
+ unlock_up(p, level, lowest_unlock,
+ min_write_lock_level, &write_lock_level);
if (level == lowest_level) {
if (dec)
@@ -1870,7 +1880,8 @@ cow_done:
}
}
if (!p->search_for_split)
- unlock_up(p, level, lowest_unlock);
+ unlock_up(p, level, lowest_unlock,
+ min_write_lock_level, &write_lock_level);
goto done;
}
}
@@ -4108,7 +4119,7 @@ find_next_key:
path->slots[level] = slot;
if (level == path->lowest_level) {
ret = 0;
- unlock_up(path, level, 1);
+ unlock_up(path, level, 1, 0, NULL);
goto out;
}
btrfs_set_path_blocking(path);
@@ -4119,7 +4130,7 @@ find_next_key:
path->locks[level - 1] = BTRFS_READ_LOCK;
path->nodes[level - 1] = cur;
- unlock_up(path, level, 1);
+ unlock_up(path, level, 1, 0, NULL);
btrfs_clear_path_blocking(path, NULL, 0);
}
out:
@@ -4355,7 +4366,7 @@ again:
}
ret = 0;
done:
- unlock_up(path, 0, 1);
+ unlock_up(path, 0, 1, 0, NULL);
path->leave_spinning = old_spinning;
if (!old_spinning)
btrfs_set_path_blocking(path);