1. 29 Oct, 2002 10 commits
    • Andrew Morton's avatar
      [PATCH] radix_tree_gang_lookup fix · 7d196748
      Andrew Morton authored
      When performing lookups against very sparse trees
      radix_tree_gang_lookup fails to find nodes "far" to the right of the
      start point.  Because it only understands sparseness in the leaf nodes,
      not the intermediate nodes.
      
      Nobody noticed this because all callers are incrementing the start
      index as they walk the tree.
      
      Change it to terminate the search when it really has inspected the last
      possible node for the current tree's height.
      7d196748
    • Andrew Morton's avatar
      [PATCH] less buslocked operations in the page allocator · f5046231
      Andrew Morton authored
      Sort-of-but-not-really from High Dickins.
      
      We're doing a lot of buslocked operations in the page allocator just
      for debug.  Plus when they _do_ trigger, there are so many BUG_ONs in
      there that it's rather hard to work out from user reports which one
      actually triggered.
      
      So redo all that and also print out some more useful info about the
      page state before taking the machine out.
      
      (And yes, we need to take the machine out.  Incorrect page handling in
      there can cause file corruption).
      f5046231
    • Andrew Morton's avatar
      [PATCH] add a file_ra_state init function · 6b390b3b
      Andrew Morton authored
      Provide a function in core kernel to initialise a file_ra_state structure.
      
      Perviously this was all taken care of by the fact that new struct
      file's are all zeroed out.  But now a file_ra_state may be
      independently allocated, and we don't want users of it to have to know
      how to initialise it.
      6b390b3b
    • Andrew Morton's avatar
      [PATCH] permit direct IO with finer-than-fs-blocksize alignments · 4a4c6811
      Andrew Morton authored
      Mainly from Badari Pulavarty
      
      Traditionally we have only supported O_DIRECT I/O at an alignment and
      granularity which matches the underlying filesystem.  That typically
      means that all IO must be 4k-aligned and a multiple of 4k in size.
      
      Here, we relax that so that direct I/O happens with (typically)
      512-byte alignment and multiple-of-512-byte size.
      
      The tricky part is when a write starts and/or ends partway through a
      filesystem block which has just been added.  We need to zero out the
      parts of that block which lie outside the written region.
      
      We handle that by putting appropriately-sized parts of the ZERO_PAGE
      into sepatate BIOs.
      
      The generic_direct_IO() function has been changed so that the
      filesystem must pass in the address of the block_device against which
      the IO is to be performed.  I'd have preferred to not do this, but we
      do need that info at that time so that alignment checks can be
      performed.
      
      If the filesystem passes in a NULL block_device pointer then we fall
      back to the old behaviour - must align with the fs blocksize.
      
      There is no trivial way for userspace to know what the minimum
      alignment is - it depends on what bdev_hardsect_size() says about the
      device.  It is _usually_ 512 bytes, but not always.  This introduces
      the risk that someone will develop and test applications which work
      fine on their hardware, but will fail on someone else's hardware.
      
      It is possible to query the hardsect size using the BLKSSZGET ioctl
      against the backing block device.  This can be performed at runtime or
      at application installation time.
      4a4c6811
    • Andrew Morton's avatar
      [PATCH] restructure direct-io to suit bio_add_page · a9577554
      Andrew Morton authored
      The direct IO code was initially designed to allocate a known-sized
      BIO, to fill it with pages and to then send it off.
      
      Then along came bio_add_page().  Really, it broke direct-io.c - it
      meant that the direct-IO BIO assembly code no longer had a-priori
      knowledge of whether a page would fit into the current BIO.
      
      Our attempts to rework the initial design to play well with
      bio_add_page() really weren't adequate.  The code was getting more and
      more twisty and we kept finding corner-cases which failed.
      
      So this patch redesigns the BIO assembly and submission path of the
      direct-IO code so that it better suits the bio_add_page() semantics.
      
      It introduces another layer in the assembly phase: the 'cur_page' which
      is cached in the dio structure.
      
      The function which walks the file mapping do_direct_IO() simply emits a
      sequence of (page,offset,len,sector) quads into the next layer down -
      submit_page_section().
      
      submit_page_section() is responsible for looking for a merge of the new
      quad against the previous page section (same page).  If no merge is
      possible it passes the currently-cached page down to the next level,
      dio_send_cur_page().
      
      dio_send_cur_page() will try to add the current page to the current
      BIO.  If that fails, the current BIO is submitted for IO and we open a
      new one.
      
      So it's all nicely layered.  The assembly of sections-of-page into the
      current page closely mirrors the assembly of sections-of-BIO into the
      current BIO.
      
      At both of these levels everything is done in a "deferred" manner: try
      to merge a new request onto the currently-cached one.  If that fails
      then send the currently-cached request and then cache this one instead.
      
      Some variables have been renamed to more closely represent their usage.
      
      Some thought has been put into ownership of the various state variables
      within `struct dio'.  We were updating and inspecting these in various
      places in a rather hard-to-follow manner.  So things have been reworked
      so that particular functions "own" particular parts of the dio
      structure.  Violators have been exterminated and commentary has been
      added to describe this ownership.
      
      The handling of file holes has been simplified.
      
      As a consequence of all this, the code is clearer and simpler than it
      used to be, and it now passes the modified-for-O_DIRECT fsx-linux
      testing again.
      a9577554
    • Andrew Morton's avatar
      [PATCH] invalidate_inode_pages fixes · caa2f807
      Andrew Morton authored
      Two fixes here.
      
      First:
      
      Fixes a BUG() which occurs if you try to perform O_DIRECT IO against a
      blockdev which has an fs mounted on it.  (We should be able to do
      that).
      
      What happens is that do_invalidatepage() ends up calling
      discard_buffer() on buffers which it couldn't strip.  That clears
      buffer_mapped() against useful things like the superblock buffer_head.
      The next submit_bh() goes BUG over the write of an unmapped buffer.
      
      So just run try_to_release_page() (aka try_to_free_buffers()) on the
      invalidate path.
      
      
      Second:
      
      The invalidate_inode_pages() functions are best-effort pagecache
      shrinkers.  They are used against pages inside i_size and are not
      supposed to throw away dirty data.
      
      However it is possible for another CPU to run set_page_dirty() against
      one of these pages after invalidate_inode_pages() has decided that it
      is clean.  This could happen if someone was performing O_DIRECT IO
      against a file which was also mapped with MAP_SHARED.
      
      So recheck the dirty state of the page inside the mapping->page_lock
      and back out if the page has just been marked dirty.
      
      This will also prevent the remove_from_page_cache() BUG which will occur
      if someone marks the page dirty between the clear_page_dirty() and
      remove_from_page_cache() calls in truncate_complete_page().
      caa2f807
    • Andrew Morton's avatar
      [PATCH] libfs a_ops correctnes · 303c9cf6
      Andrew Morton authored
      simple_prepare_write() currently memsets the entire page.  It only
      needs to clear the parts which are outside the to-be-written region.
      This change makes no difference to performance - that memset was just a
      cache preload for the copy_from_user() in generic_file_write().  But
      it's more correct.
      
      Also, mark the page dirty in simple_commit_write(), not in
      simple_prepare_write().  Because the page's contents are changed after
      prepare_write().  This doesn't matter in practice, but it is setting a
      bad example.
      
      Also, add a flush_dcache_page() to simple_prepare_write().  Again, not
      really needed because the page cannot be mapped into pagetables if it
      is not uptodate.  But it is example code and should not be missing such
      things.
      303c9cf6
    • Andrew Morton's avatar
      [PATCH] move ramfs a_ops into libfs · 3ee477f0
      Andrew Morton authored
      From Bill Irwin.
      
      Abstract out ramfs readpage(), prepare_write(), and commit_write()
      operations.
      
      Ram-backed filesystems are going to be doing a lot of zero-filled read
      and write operations.  So in this patch, ramfs' implementations are
      moved to libfs in anticipation of other callers.
      3ee477f0
    • Andrew Morton's avatar
      [PATCH] blkdev_get_block fix · f596aeef
      Andrew Morton authored
      Patch from Hugh Dickins <hugh@veritas.com>
      
      Fix premature -EIO from blkdev_get_block: bdget initialize
      bd_block_size consistent with bd_inode->i_blkbits (assigned by
      new_inode).  Otherwise, subsequent set_blocksize can find bd_block_size
      doesn't need updating, and skip updating i_blkbits, leaving them
      inconsistent.
      f596aeef
    • Andrew Morton's avatar
      [PATCH] fid dmi compile warning · ba3d6419
      Andrew Morton authored
      Local variable `data' is only used for debugging.
      ba3d6419
  2. 28 Oct, 2002 30 commits