1. 30 Mar, 2010 1 commit
    • Tejun Heo's avatar
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking... · 5a0e3ad6
      Tejun Heo authored
      include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
      
      percpu.h is included by sched.h and module.h and thus ends up being
      included when building most .c files.  percpu.h includes slab.h which
      in turn includes gfp.h making everything defined by the two files
      universally available and complicating inclusion dependencies.
      
      percpu.h -> slab.h dependency is about to be removed.  Prepare for
      this change by updating users of gfp and slab facilities include those
      headers directly instead of assuming availability.  As this conversion
      needs to touch large number of source files, the following script is
      used as the basis of conversion.
      
        http://userweb.kernel.org/~tj/misc/slabh-sweep.py
      
      
      
      The script does the followings.
      
      * Scan files for gfp and slab usages and update includes such that
        only the necessary includes are there.  ie. if only gfp is used,
        gfp.h, if slab is used, slab.h.
      
      * When the script inserts a new include, it looks at the include
        blocks and try to put the new include such that its order conforms
        to its surrounding.  It's put in the include block which contains
        core kernel includes, in the same order that the rest are ordered -
        alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
        doesn't seem to be any matching order.
      
      * If the script can't find a place to put a new include (mostly
        because the file doesn't have fitting include block), it prints out
        an error message indicating which .h file needs to be added to the
        file.
      
      The conversion was done in the following steps.
      
      1. The initial automatic conversion of all .c files updated slightly
         over 4000 files, deleting around 700 includes and adding ~480 gfp.h
         and ~3000 slab.h inclusions.  The script emitted errors for ~400
         files.
      
      2. Each error was manually checked.  Some didn't need the inclusion,
         some needed manual addition while adding it to implementation .h or
         embedding .c file was more appropriate for others.  This step added
         inclusions to around 150 files.
      
      3. The script was run again and the output was compared to the edits
         from #2 to make sure no file was left behind.
      
      4. Several build tests were done and a couple of problems were fixed.
         e.g. lib/decompress_*.c used malloc/free() wrappers around slab
         APIs requiring slab.h to be added manually.
      
      5. The script was run on all .h files but without automatically
         editing them as sprinkling gfp.h and slab.h inclusions around .h
         files could easily lead to inclusion dependency hell.  Most gfp.h
         inclusion directives were ignored as stuff from gfp.h was usually
         wildly available and often used in preprocessor macros.  Each
         slab.h inclusion directive was examined and added manually as
         necessary.
      
      6. percpu.h was updated not to include slab.h.
      
      7. Build test were done on the following configurations and failures
         were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
         distributed build env didn't work with gcov compiles) and a few
         more options had to be turned off depending on archs to make things
         build (like ipr on powerpc/64 which failed due to missing writeq).
      
         * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
         * powerpc and powerpc64 SMP allmodconfig
         * sparc and sparc64 SMP allmodconfig
         * ia64 SMP allmodconfig
         * s390 SMP allmodconfig
         * alpha SMP allmodconfig
         * um on x86_64 SMP allmodconfig
      
      8. percpu.h modifications were reverted so that it could be applied as
         a separate patch and serve as bisection point.
      
      Given the fact that I had only a couple of failures from tests on step
      6, I'm fairly confident about the coverage of this conversion patch.
      If there is a breakage, it's likely to be something in one of the arch
      headers which should be easily discoverable easily on most builds of
      the specific arch.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Guess-its-ok-by: default avatarChristoph Lameter <cl@linux-foundation.org>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
      5a0e3ad6
  2. 04 Feb, 2009 1 commit
    • Chris Mason's avatar
      Btrfs: Make btrfs_drop_snapshot work in larger and more efficient chunks · bd56b302
      Chris Mason authored
      
      Every transaction in btrfs creates a new snapshot, and then schedules the
      snapshot from the last transaction for deletion.  Snapshot deletion
      works by walking down the btree and dropping the reference counts
      on each btree block during the walk.
      
      If if a given leaf or node has a reference count greater than one,
      the reference count is decremented and the subtree pointed to by that
      node is ignored.
      
      If the reference count is one, walking continues down into that node
      or leaf, and the references of everything it points to are decremented.
      
      The old code would try to work in small pieces, walking down the tree
      until it found the lowest leaf or node to free and then returning.  This
      was very friendly to the rest of the FS because it didn't have a huge
      impact on other operations.
      
      But it wouldn't always keep up with the rate that new commits added new
      snapshots for deletion, and it wasn't very optimal for the extent
      allocation tree because it wasn't finding leaves that were close together
      on disk and processing them at the same time.
      
      This changes things to walk down to a level 1 node and then process it
      in bulk.  All the leaf pointers are sorted and the leaves are dropped
      in order based on their extent number.
      
      The extent allocation tree and commit code are now fast enough for
      this kind of bulk processing to work without slowing the rest of the FS
      down.  Overall it does less IO and is better able to keep up with
      snapshot deletions under high load.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      bd56b302
  3. 05 Jan, 2009 1 commit
  4. 29 Sep, 2008 2 commits
    • Chris Mason's avatar
      Btrfs: add and improve comments · d352ac68
      Chris Mason authored
      
      This improves the comments at the top of many functions.  It didn't
      dive into the guts of functions because I was trying to
      avoid merging problems with the new allocator and back reference work.
      
      extent-tree.c and volumes.c were both skipped, and there is definitely
      more work todo in cleaning and commenting the code.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      d352ac68
    • Chris Mason's avatar
      Btrfs: drop WARN_ON from btrfs_add_leaf_ref · 9a5e1ea1
      Chris Mason authored
      
      btrfs_add_leaf_ref was doing checks on the objects it found in the
      rbtree to make sure they were properly linked into the tree.  But, the field
      it was checking can be safely changed outside of the tree spin lock.
      
      The WARN_ON was for debugging the initial implementation and can be
      safely removed.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      9a5e1ea1
  5. 26 Sep, 2008 1 commit
    • Zheng Yan's avatar
      Btrfs: Add shared reference cache · e4657689
      Zheng Yan authored
      
      Btrfs has a cache of reference counts in leaves, allowing it to
      avoid reading tree leaves while deleting snapshots.  To reduce
      contention with multiple subvolumes, this cache is private to each
      subvolume.
      
      This patch adds shared reference cache support. The new space
      balancing code plays with multiple subvols at the same time, So
      the old per-subvol reference cache is not well suited.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      e4657689
  6. 25 Sep, 2008 3 commits
    • Yan's avatar
      Btrfs: implement memory reclaim for leaf reference cache · bcc63abb
      Yan authored
      
      The memory reclaiming issue happens when snapshot exists. In that
      case, some cache entries may not be used during old snapshot dropping,
      so they will remain in the cache until umount.
      
      The patch adds a field to struct btrfs_leaf_ref to record create time. Besides,
      the patch makes all dead roots of a given snapshot linked together in order of
      create time. After a old snapshot was completely dropped, we check the dead
      root list and remove all cache entries created before the oldest dead root in
      the list.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      bcc63abb
    • Chris Mason's avatar
      Btrfs: Leaf reference cache update · 017e5369
      Chris Mason authored
      
      This changes the reference cache to make a single cache per root
      instead of one cache per transaction, and to key by the byte number
      of the disk block instead of the keys inside.
      
      This makes it much less likely to have cache misses if a snapshot
      or something has an extra reference on a higher node or a leaf while
      the first transaction that added the leaf into the cache is dropping.
      
      Some throttling is added to functions that free blocks heavily so they
      wait for old transactions to drop.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      017e5369
    • Yan Zheng's avatar
      Btrfs: Add a leaf reference cache · 31153d81
      Yan Zheng authored
      
      Much of the IO done while dropping snapshots is done looking up
      leaves in the filesystem trees to see if they point to any extents and
      to drop the references on any extents found.
      
      This creates a cache so that IO isn't required.
      Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
      31153d81