1. 24 Feb, 2011 1 commit
    • Miklos Szeredi's avatar
      mm: prevent concurrent unmap_mapping_range() on the same inode · 2aa15890
      Miklos Szeredi authored
      
      
      Michael Leun reported that running parallel opens on a fuse filesystem
      can trigger a "kernel BUG at mm/truncate.c:475"
      
      Gurudas Pai reported the same bug on NFS.
      
      The reason is, unmap_mapping_range() is not prepared for more than
      one concurrent invocation per inode.  For example:
      
        thread1: going through a big range, stops in the middle of a vma and
           stores the restart address in vm_truncate_count.
      
        thread2: comes in with a small (e.g. single page) unmap request on
           the same vma, somewhere before restart_address, finds that the
           vma was already unmapped up to the restart address and happily
           returns without doing anything.
      
      Another scenario would be two big unmap requests, both having to
      restart the unmapping and each one setting vm_truncate_count to its
      own value.  This could go on forever without any of them being able to
      finish.
      
      Truncate and hole punching already serialize with i_mutex.  Other
      callers of unmap_mapping_range() do not, and it's difficult to get
      i_mutex protection for all callers.  In particular ->d_revalidate(),
      which calls invalidate_inode_pages2_range() in fuse, may be called
      with or without i_mutex.
      
      This patch adds a new mutex to 'struct address_space' to prevent
      running multiple concurrent unmap_mapping_range() on the same mapping.
      
      [ We'll hopefully get rid of all this with the upcoming mm
        preemptibility series by Peter Zijlstra, the "mm: Remove i_mmap_mutex
        lockbreak" patch in particular.  But that is for 2.6.39 ]
      Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
      Reported-by: default avatarMichael Leun <lkml20101129@newton.leun.net>
      Reported-by: default avatarGurudas Pai <gurudas.pai@oracle.com>
      Tested-by: default avatarGurudas Pai <gurudas.pai@oracle.com>
      Acked-by: default avatarHugh Dickins <hughd@google.com>
      Cc: stable@kernel.org
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      2aa15890
  2. 10 Jan, 2011 1 commit
    • Ryusuke Konishi's avatar
      nilfs2: fiemap support · 622daaff
      Ryusuke Konishi authored
      
      
      This adds fiemap to nilfs.  Two new functions, nilfs_fiemap and
      nilfs_find_uncommitted_extent are added.
      
      nilfs_fiemap() implements the fiemap inode operation, and
      nilfs_find_uncommitted_extent() helps to get a range of data blocks
      whose physical location has not been determined.
      
      nilfs_fiemap() collects extent information by looping through
      nilfs_bmap_lookup_contig and nilfs_find_uncommitted_extent routines.
      Signed-off-by: default avatarRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
      622daaff
  3. 23 Oct, 2010 2 commits
    • Ryusuke Konishi's avatar
      nilfs2: add routines to redirect access to buffers of DAT file · b1f6a4f2
      Ryusuke Konishi authored
      
      
      During garbage collection (GC), DAT file, which converts virtual block
      number to real block number, may return disk block number that is not
      yet written to the device.
      
      To avoid access to unwritten blocks, the current implementation stores
      changes to the caches of GCDAT during GC and atomically commit the
      changes into the DAT file after they are written to the device.
      
      This patch, instead, adds a function that makes a copy of specified
      buffer and stores it in nilfs_shadow_map, and a function to get the
      backup copy as needed (nilfs_mdt_freeze_buffer and
      nilfs_mdt_get_frozen_buffer respectively).
      
      Before DAT changes block number in an entry block, it makes a copy and
      redirect access to the buffer so that address conversion function
      (i.e. nilfs_dat_translate) refers to the old address saved in the
      copy.
      
      This patch gives requisites for such redirection.
      Signed-off-by: default avatarRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
      b1f6a4f2
    • Ryusuke Konishi's avatar
      nilfs2: add routines to roll back state of DAT file · ebdfed4d
      Ryusuke Konishi authored
      
      
      This adds optional function to metadata files which makes a copy of
      bmap, page caches, and b-tree node cache, and rolls back to the copy
      as needed.
      
      This enhancement is intended to displace gcdat inode that provides a
      similar function in a different way.
      
      In this patch, nilfs_shadow_map structure is added to store a copy of
      the foregoing states.  nilfs_mdt_setup_shadow_map relates this
      structure to a metadata file.  And, nilfs_mdt_save_to_shadow_map() and
      nilfs_mdt_restore_from_shadow_map() provides save and restore
      functions respectively.  Finally, nilfs_mdt_clear_shadow_map() clears
      states of nilfs_shadow_map.
      
      The copy of b-tree node cache and page cache is made by duplicating
      only dirty pages into corresponding caches in nilfs_shadow_map.  Their
      restoration is done by clearing dirty pages from original caches and
      by copying dirty pages back from nilfs_shadow_map.
      Signed-off-by: default avatarRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
      ebdfed4d
  4. 23 Jul, 2010 1 commit
  5. 07 Apr, 2009 1 commit
    • Ryusuke Konishi's avatar
      nilfs2: buffer and page operations · 0bd49f94
      Ryusuke Konishi authored
      
      
      This adds common routines for buffer/page operations used in B-tree
      node caches, meta data files, or segment constructor (log writer).
      
      NILFS uses copy functions for buffers and pages due to the following
      reasons:
      
       1) Relocation required for COW
          Since NILFS changes address of on-disk blocks, moving buffers
          in page cache is needed for the buffers which are not addressed
          by a file offset.  If buffer size is smaller than page size,
          this involves partial copy of pages.
      
       2) Freezing mmapped pages
          NILFS calculates checksums for each log to ensure its validity.
          If page data changes after the checksum calculation, this validity
          check will not work correctly.  To avoid this failure for mmaped
          pages, NILFS freezes their data by copying.
      
       3) Copy-on-write for DAT pages
          NILFS makes clones of DAT page caches in a copy-on-write manner
          during GC processes, and this ensures atomicity and consistency
          of the DAT in the transient state.
      
      In addition, NILFS uses two obsolete functions, nilfs_mark_buffer_dirty()
      and nilfs_clear_page_dirty() respectively.
      
      * nilfs_mark_buffer_dirty() was required to avoid NULL pointer
        dereference faults:
      
        Since the page cache of B-tree node pages or data page cache of pseudo
        inodes does not have a valid mapping->host, calling mark_buffer_dirty()
        for their buffers causes the fault; it calls __mark_inode_dirty(NULL)
        through __set_page_dirty().
      
      * nilfs_clear_page_dirty() was needed in the two cases:
      
       1) For B-tree node pages and data pages of the dat/gcdat, NILFS2 clears
          page dirty flags when it copies back pages from the cloned cache
          (gcdat->{i_mapping,i_btnode_cache}) to its original cache
          (dat->{i_mapping,i_btnode_cache}).
      
       2) Some B-tree operations like insertion or deletion may dispose buffers
          in dirty state, and this needs to cancel the dirty state of their
          pages.  clear_page_dirty_for_io() caused faults because it does not
          clear the dirty tag on the page cache.
      Signed-off-by: default avatarSeiji Kihara <kihara.seiji@lab.ntt.co.jp>
      Signed-off-by: default avatarRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0bd49f94