Btrfs: Subpagesize-blocksize: Allow I/O on blocks whose size is less than page size

Btrfs assumes block size to be the same as the machine's page
size. This would mean that a Btrfs instance created on a 4k page size
machine (e.g. x86) will not be mountable on machines with larger page
sizes (e.g. PPC64/AARCH64). This patchset aims to resolve this
incompatibility.

This patchset continues with the work posted previously at
http://thread.gmane.org/gmane.comp.file-systems.btrfs/52815.

I have reverted the upstream commit "btrfs: fix lockups from
btrfs_clear_path_blocking" (f82c458a2c3ffb94b431fc6ad791a79df1b3713e)
since this led to soft-lockups when the patch "Btrfs:
subpagesize-blocksize: Prevent writes to an extent buffer when
PG_writeback flag is set" is applied. During 2015's Vault Conference
Btrfs meetup, Chris Mason had suggested that he will write up a
suitable locking function to be used when writing dirty pages that map
metadata blocks. Until we have a suitable locking function available,
this patchset temporarily disables the commit
f82c458a2c3ffb94b431fc6ad791a79df1b3713e.

The commits for the Btrfs kernel module can be found at
https://github.com/chandanr/linux/tree/btrfs/subpagesize-....

To create a filesystem with block size < page size, a patched version
of the Btrfs-progs package is required. The corresponding fixes for
Btrfs-progs can be found at
https://github.com/chandanr/btrfs-progs/tree/btrfs/subpag....

Fstests run status:
1. x86_64
   - With 4k sectorsize, all the tests that succeed with
     linux-btrfs/integration-4.5 branch also do so with the patches
     applied.
   - With 2k sectorsize, all the *generic* tests that succeed with
     linux-btrfs/integration-4.5 branch also do so with the patches
     applied.
2. ppc64
   - With 4k sectorsize, 16k nodesize and with "nospace_cache" mount
     option, all the *generic* tests that succeed with
     linux-btrfs/integration-4.5 branch also do so with the patches
     applied.
   - With 64k sectorsize & nodesize, all the tests that succeed with
     linux-btrfs/integration-4.5 branch also do so with the patches
     applied.

Changes from V14:
1. Fix usage of cleancache_get_page() in __do_readpage().
   In filesystems which support subpage-blocksize scenario, a page can
   map one or more blocks. Hence cleancache_get_page() should be
   invoked only when the page maps a non-hole extent and block size
   being used is equal to the page size. Thanks to David Sterba for
   pointing this out.
2. Replace page_read_complete() and page_write_complete() functions
   with page_io_complete().
3. Provide more documentation (as part of both commit message and code
   comments) about the usage of the per-page
   btrfs_page_private->io_lock.

Changes from V13:
1. Enable dedup ioctl to work in subpagesize-blocksize scenario.

Changes from V12:
1. The logic in the function btrfs_punch_hole() has been fixed to
   check for the presence of BLK_STATE_UPTODATE flags for blocks in
   pages which partially map the file range being punched.
   
Changes from V11:
1. Addressed the review comments provided by Liu Bo for version V11.
2. Fixed file defragmentation code to work in subpagesize-blocksize
   scenario.
3. Many "hard to reproduce" bugs were fixed.

Chandan Rajendra (15):
  Btrfs: subpage-blocksize: Fix whole page read.
  Btrfs: subpage-blocksize: Fix whole page write
  Btrfs: subpage-blocksize: Make sure delalloc range intersects with the
    locked page's range
  Btrfs: subpage-blocksize: Define extent_buffer_head.
  Btrfs: subpage-blocksize: Read tree blocks whose size is < PAGE_SIZE.
  Btrfs: subpage-blocksize: Write only dirty extent buffers belonging to
    a page
  Btrfs: subpage-blocksize: Allow mounting filesystems where sectorsize
    != PAGE_SIZE
  Btrfs: subpage-blocksize: Deal with partial ordered extent
    allocations.
  Btrfs: subpage-blocksize: Explicitly track I/O status of blocks of an
    ordered extent.
  Btrfs: subpage-blocksize: btrfs_punch_hole: Fix uptodate blocks check
  Btrfs: subpage-blocksize: Prevent writes to an extent buffer when
    PG_writeback flag is set.
  Revert "btrfs: fix lockups from btrfs_clear_path_blocking"
  Btrfs: subpage-blocksize: Fix file defragmentation code
  Btrfs: subpage-blocksize: extent_clear_unlock_delalloc: Prevent page
    from being unlocked more than once
  Btrfs: subpage-blocksize: Enable dedup ioctl

 fs/btrfs/backref.c           |    2 +-
 fs/btrfs/ctree.c             |   37 +-
 fs/btrfs/ctree.h             |    6 +-
 fs/btrfs/disk-io.c           |  161 +++--
 fs/btrfs/disk-io.h           |    3 +
 fs/btrfs/extent-tree.c       |   17 +-
 fs/btrfs/extent_io.c         | 1615 +++++++++++++++++++++++++++++-------------
 fs/btrfs/extent_io.h         |  144 +++-
 fs/btrfs/file.c              |   82 ++-
 fs/btrfs/inode.c             |  491 +++++++++----
 fs/btrfs/ioctl.c             |  205 ++++--
 fs/btrfs/locking.c           |   24 +-
 fs/btrfs/locking.h           |    2 -
 fs/btrfs/ordered-data.c      |   19 +
 fs/btrfs/ordered-data.h      |    4 +
 fs/btrfs/relocation.c        |    3 +
 fs/btrfs/root-tree.c         |    2 +-
 fs/btrfs/volumes.c           |    2 +-
 include/trace/events/btrfs.h |    2 +-
 19 files changed, 2009 insertions(+), 812 deletions(-)

-- 
2.1.0

--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html