[Patch 5/10]: ext3 online resize: lock newly-created buffers

From: Stephen Tweedie (sct_at_redhat.com)
Date: 09/30/04

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    Date:	Thu, 30 Sep 2004 14:23:39 +0100
To: linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>, Andreas Dilger <adilger@clusterfs.com>, "Theodore Ts'o" <tytso@mit.edu>, ext2-devel@lists.sourceforge.net

    Lock buffers before initialising their contents to avoid any risk of
    being overwritten by the results of a parallel read.

    Signed-off-by: Stephen Tweedie <sct@redhat.com>

    --- linux-2.6.9-rc2-mm4/fs/ext3/resize.c.=K0004=.orig
    +++ linux-2.6.9-rc2-mm4/fs/ext3/resize.c
    @@ -118,13 +118,16 @@ static struct buffer_head *bclean(handle
             int err;
     
             bh = sb_getblk(sb, blk);
    - set_buffer_uptodate(bh);
             if ((err = ext3_journal_get_write_access(handle, bh))) {
                     brelse(bh);
                     bh = ERR_PTR(err);
    - } else
    + } else {
    + lock_buffer(bh);
                     memset(bh->b_data, 0, sb->s_blocksize);
    -
    + set_buffer_uptodate(bh);
    + unlock_buffer(bh);
    + }
    +
             return bh;
     }
     
    @@ -201,12 +204,14 @@ static int setup_new_group_blocks(struct
                     ext3_debug("update backup group %#04lx (+%d)\n", block, bit);
     
                     gdb = sb_getblk(sb, block);
    - set_buffer_uptodate(gdb);
                     if ((err = ext3_journal_get_write_access(handle, gdb))) {
                             brelse(gdb);
                             goto exit_bh;
                     }
    + lock_buffer(bh);
                     memcpy(gdb->b_data, sbi->s_group_desc[i], bh->b_size);
    + set_buffer_uptodate(gdb);
    + unlock_buffer(bh);
                     ext3_journal_dirty_metadata(handle, gdb);
                     ext3_set_bit(bit, bh->b_data);
                     brelse(gdb);
    @@ -642,14 +647,16 @@ static void update_backups(struct super_
                             break;
     
                     bh = sb_getblk(sb, group * bpg + blk_off);
    - set_buffer_uptodate(bh);
                     ext3_debug(sb, __FUNCTION__, "update metadata backup %#04lx\n",
                                bh->b_blocknr);
                     if ((err = ext3_journal_get_write_access(handle, bh)))
                             break;
    + lock_buffer(bh);
                     memcpy(bh->b_data, data, size);
                     if (rest)
                             memset(bh->b_data + size, 0, rest);
    + set_buffer_uptodate(bh);
    + unlock_buffer(bh);
                     ext3_journal_dirty_metadata(handle, bh);
                     brelse(bh);
             }
    -
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