zygo: cherry-picked b4caecd

de1414a
b83ae6d
df0ce26
8d38633
575849e
f55985f
13212b5
3e05bde
3266789
dcab6a3
3d84be7
1a4bcf4
a742994

Included commits:

575849e Btrfs: fix scheduler warning when syncing log
f55985f Btrfs: scrub, fix sleep in atomic context
13212b5 btrfs: Fix out-of-space bug
3e05bde Btrfs: only adjust outstanding_extents when we do a short write
3266789 Btrfs: don't set and clear delalloc for O_DIRECT writes
dcab6a3 Btrfs: account for large extents with enospc
3d84be7 Btrfs: fix BUG_ON in btrfs_orphan_add() when delete unused block group
1a4bcf4 Btrfs: fix fsync data loss after adding hard link to inode
a742994 Btrfs: don't remove extents and xattrs when logging new names

Excluded commits:

b4caecd fs: introduce f_op->mmap_capabilities for nommu mmap support
de1414a fs: export inode_to_bdi and use it in favor of mapping->backing_dev_info
b83ae6d fs: remove mapping->backing_dev_info
df0ce26 fs: remove default_backing_dev_info
8d38633 page_writeback: put account_page_redirty() after set_page_dirty()