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>
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b9473439d3
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@ -1497,6 +1497,30 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
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return 0;
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return 0;
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}
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}
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/*
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* helper function for btrfs_finish_ordered_io, this
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* just reads in some of the csum leaves to prime them into ram
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* before we start the transaction. It limits the amount of btree
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* reads required while inside the transaction.
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*/
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static noinline void reada_csum(struct btrfs_root *root,
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struct btrfs_path *path,
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struct btrfs_ordered_extent *ordered_extent)
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{
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struct btrfs_ordered_sum *sum;
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u64 bytenr;
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sum = list_entry(ordered_extent->list.next, struct btrfs_ordered_sum,
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list);
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bytenr = sum->sums[0].bytenr;
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/*
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* we don't care about the results, the point of this search is
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* just to get the btree leaves into ram
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*/
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btrfs_lookup_csum(NULL, root->fs_info->csum_root, path, bytenr, 0);
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}
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/* as ordered data IO finishes, this gets called so we can finish
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/* as ordered data IO finishes, this gets called so we can finish
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* an ordered extent if the range of bytes in the file it covers are
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* an ordered extent if the range of bytes in the file it covers are
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* fully written.
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* fully written.
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@ -1505,7 +1529,7 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
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{
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{
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struct btrfs_root *root = BTRFS_I(inode)->root;
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struct btrfs_root *root = BTRFS_I(inode)->root;
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struct btrfs_trans_handle *trans;
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struct btrfs_trans_handle *trans;
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struct btrfs_ordered_extent *ordered_extent;
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struct btrfs_ordered_extent *ordered_extent = NULL;
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struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
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struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
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struct btrfs_path *path;
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struct btrfs_path *path;
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int compressed = 0;
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int compressed = 0;
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@ -1528,13 +1552,20 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
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ret = btrfs_lookup_file_extent(NULL, root, path,
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ret = btrfs_lookup_file_extent(NULL, root, path,
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inode->i_ino,
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inode->i_ino,
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start, 0);
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start, 0);
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ordered_extent = btrfs_lookup_ordered_extent(inode,
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start);
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if (!list_empty(&ordered_extent->list)) {
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btrfs_release_path(root, path);
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reada_csum(root, path, ordered_extent);
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}
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btrfs_free_path(path);
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btrfs_free_path(path);
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}
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}
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}
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}
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trans = btrfs_join_transaction(root, 1);
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trans = btrfs_join_transaction(root, 1);
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ordered_extent = btrfs_lookup_ordered_extent(inode, start);
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if (!ordered_extent)
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ordered_extent = btrfs_lookup_ordered_extent(inode, start);
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BUG_ON(!ordered_extent);
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BUG_ON(!ordered_extent);
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if (test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags))
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if (test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags))
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goto nocow;
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goto nocow;
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