Btrfs: cache extent states in defrag code path

When locking file ranges in the inode's io_tree, cache the first
extent state that belongs to the target range, so that when unlocking
the range we don't need to search in the io_tree again, reducing cpu
time and making and therefore holding the io_tree's lock for a shorter
period.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index e174770..3ad5c10 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -986,10 +986,13 @@ static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start)
        read_unlock(&em_tree->lock);
 
        if (!em) {
+               struct extent_state *cached = NULL;
+               u64 end = start + len - 1;
+
                /* get the big lock and read metadata off disk */
-               lock_extent(io_tree, start, start + len - 1);
+               lock_extent_bits(io_tree, start, end, 0, &cached);
                em = btrfs_get_extent(inode, NULL, 0, start, len, 0);
-               unlock_extent(io_tree, start, start + len - 1);
+               unlock_extent_cached(io_tree, start, end, &cached, GFP_NOFS);
 
                if (IS_ERR(em))
                        return NULL;
@@ -1128,10 +1131,12 @@ again:
                page_start = page_offset(page);
                page_end = page_start + PAGE_CACHE_SIZE - 1;
                while (1) {
-                       lock_extent(tree, page_start, page_end);
+                       lock_extent_bits(tree, page_start, page_end,
+                                        0, &cached_state);
                        ordered = btrfs_lookup_ordered_extent(inode,
                                                              page_start);
-                       unlock_extent(tree, page_start, page_end);
+                       unlock_extent_cached(tree, page_start, page_end,
+                                            &cached_state, GFP_NOFS);
                        if (!ordered)
                                break;