From: Dmitry Monakhov <dmonakhov@openvz.org>
Date: Fri, 5 Oct 2012 15:32:02 +0000 (-0400)
Subject: ext4: serialize fallocate with ext4_convert_unwritten_extents
X-Git-Tag: v3.7-rc3~47^2~5
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=60d4616f3dc63371b3dc367e5e88fd4b4f037f65;p=pandora-kernel.git

ext4: serialize fallocate with ext4_convert_unwritten_extents

Fallocate should wait for pended ext4_convert_unwritten_extents()
otherwise following race may happen:

ftruncate( ,12288);
fallocate( ,0, 4096)
io_sibmit( ,0, 4096); /* Write to fallocated area, split extent if needed */
fallocate( ,0, 8192); /* Grow extent and broke assumption about extent */

Later kwork completion will do:
 ->ext4_convert_unwritten_extents (0, 4096)
   ->ext4_map_blocks(handle, inode, &map, EXT4_GET_BLOCKS_IO_CONVERT_EXT);
    ->ext4_ext_map_blocks() /* Will find new extent:  ex = [0,2] !!!!!! */
      ->ext4_ext_handle_uninitialized_extents()
        ->ext4_convert_unwritten_extents_endio()
        /* convert [0,2] extent to initialized, but only[0,1] was written */

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---

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