Btrfs: reduce lock contention during extent insertion
We're spending huge amounts of time on lock contention during end_io processing because we unconditionally assume we are overwriting an existing extent in the file for each IO. This checks to see if we are outside i_size, and if so, it uses a less expensive readonly search of the btree to look for existing extents. Signed-off-by: Chris Mason <chris.mason@oracle.com>
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@ -567,6 +567,7 @@ int btrfs_drop_extents(struct btrfs_trans_handle *trans, struct inode *inode,
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int extent_type;
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int recow;
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int ret;
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int modify_tree = -1;
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if (drop_cache)
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btrfs_drop_extent_cache(inode, start, end - 1, 0);
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@ -575,10 +576,13 @@ int btrfs_drop_extents(struct btrfs_trans_handle *trans, struct inode *inode,
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if (!path)
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return -ENOMEM;
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if (start >= BTRFS_I(inode)->disk_i_size)
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modify_tree = 0;
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while (1) {
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recow = 0;
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ret = btrfs_lookup_file_extent(trans, root, path, ino,
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search_start, -1);
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search_start, modify_tree);
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if (ret < 0)
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break;
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if (ret > 0 && path->slots[0] > 0 && search_start == start) {
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@ -634,7 +638,8 @@ next_slot:
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}
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search_start = max(key.offset, start);
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if (recow) {
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if (recow || !modify_tree) {
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modify_tree = -1;
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btrfs_release_path(path);
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continue;
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}
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