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authorChris Mason <chris.mason@oracle.com>2009-03-13 11:41:46 -0400
committerChris Mason <chris.mason@oracle.com>2009-03-24 16:14:51 -0400
commit5d13a98f3bf5afc1113f7db184c627a44659bc29 (patch)
tree1b9e7f2ed6047e9f471fd6f3b9e665c74dd5910b /fs/btrfs/inode.c
parentb9473439d3e84d9fc1a0a83faca69cc1b7566341 (diff)
Btrfs: readahead checksums during btrfs_finish_ordered_io
This reads in blocks in the checksum btree before starting the transaction in btrfs_finish_ordered_io. It makes it much more likely we'll be able to do operations inside the transaction without needing any btree reads, which limits transaction latencies overall. Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/inode.c')
-rw-r--r--fs/btrfs/inode.c35
1 files changed, 33 insertions, 2 deletions
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b83a45dc717..9b4faac50c1 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1497,6 +1497,30 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
return 0;
}
+/*
+ * helper function for btrfs_finish_ordered_io, this
+ * just reads in some of the csum leaves to prime them into ram
+ * before we start the transaction. It limits the amount of btree
+ * reads required while inside the transaction.
+ */
+static noinline void reada_csum(struct btrfs_root *root,
+ struct btrfs_path *path,
+ struct btrfs_ordered_extent *ordered_extent)
+{
+ struct btrfs_ordered_sum *sum;
+ u64 bytenr;
+
+ sum = list_entry(ordered_extent->list.next, struct btrfs_ordered_sum,
+ list);
+ bytenr = sum->sums[0].bytenr;
+
+ /*
+ * we don't care about the results, the point of this search is
+ * just to get the btree leaves into ram
+ */
+ btrfs_lookup_csum(NULL, root->fs_info->csum_root, path, bytenr, 0);
+}
+
/* as ordered data IO finishes, this gets called so we can finish
* an ordered extent if the range of bytes in the file it covers are
* fully written.
@@ -1505,7 +1529,7 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
{
struct btrfs_root *root = BTRFS_I(inode)->root;
struct btrfs_trans_handle *trans;
- struct btrfs_ordered_extent *ordered_extent;
+ struct btrfs_ordered_extent *ordered_extent = NULL;
struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
struct btrfs_path *path;
int compressed = 0;
@@ -1528,13 +1552,20 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
ret = btrfs_lookup_file_extent(NULL, root, path,
inode->i_ino,
start, 0);
+ ordered_extent = btrfs_lookup_ordered_extent(inode,
+ start);
+ if (!list_empty(&ordered_extent->list)) {
+ btrfs_release_path(root, path);
+ reada_csum(root, path, ordered_extent);
+ }
btrfs_free_path(path);
}
}
trans = btrfs_join_transaction(root, 1);
- ordered_extent = btrfs_lookup_ordered_extent(inode, start);
+ if (!ordered_extent)
+ ordered_extent = btrfs_lookup_ordered_extent(inode, start);
BUG_ON(!ordered_extent);
if (test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags))
goto nocow;