Here is a series which simplifies the way eb are used in EXTENT_BUFFER_UNMAPPED context. The end goal was to remove the special "if we have ref count of 2 and EXTENT_BUFFER_UNMAPPED flag then act as if this is the last ref and free the buffer" case. To enable this the first 6 patches modify call sites which needlessly bump the reference count.
Patch 1 & 2 remove some btree locking when we are operating on unmapped extent buffers. Each patch's changelog explains why this is safe to do . Patch 3,4,5 and 6 remove redundant calls to extent_buffer_get since they don't really add any value. In all 3 cases having a reference count of 1 is sufficient for the eb to be freed via btrfs_release_path. Patch 7 removes the special handling of EXTENT_BUFFER_UNMAPPED flag in free_extent_buffer. Also adjust the selftest code to account for this change by calling one extra time free_extent_buffer. Also document which references are being dropped. All in all this shouldn't have any functional bearing. This was tested with multiple full xfstest runs as well as unloading the btrfs module after each one to trigger the leak check and ensure no eb's are leaked. I've also run it through btrfs' selftests multiple times with no problems. With this set applied EXTENT_BUFFER_UNMAPPED seems to be relevant only for selftest which leads me to believe it can be removed altogether. I will investigate this next but in the meantime this series should be good to go. Nikolay Borisov (7): btrfs: Remove needless locking in iterate_inode_refs btrfs: Remove needless locking in iterate_inode_extrefs btrfs: Remove redundant extent_buffer_get in get_old_root btrfs: Remove extraneous extent_buffer_get from tree_mod_log_rewind btrfs: Remove extra reference count bumps in btrfs_compare_trees btrfs: Remove unnecessary locking code in qgroup_rescan_leaf btrfs: Remove special handling of EXTENT_BUFFER_UNMAPPED while freeing fs/btrfs/backref.c | 9 --------- fs/btrfs/ctree.c | 4 ---- fs/btrfs/extent_io.c | 11 ----------- fs/btrfs/qgroup.c | 7 +------ fs/btrfs/tests/btrfs-tests.c | 6 +++++- 5 files changed, 6 insertions(+), 31 deletions(-) -- 2.7.4
