From: Lachlan McIlroy Date: Wed, 17 Sep 2008 06:50:14 +0000 (+1000) Subject: [XFS] Prevent direct I/O from mapping extents beyond eof X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=364f358a734ddcd827c662ccbfa58ee3ac510762;p=linux-2.6 [XFS] Prevent direct I/O from mapping extents beyond eof With the help from some tracing I found that we try to map extents beyond eof when doing a direct I/O read. It appears that the way to inform the generic direct I/O path (ie do_direct_IO()) that we have breached eof is to return an unmapped buffer from xfs_get_blocks_direct(). This will cause do_direct_IO() to jump to the hole handling code where is will check for eof and then abort. This problem was found because a direct I/O read was trying to map beyond eof and was encountering delayed allocations. The delayed allocations beyond eof are speculative allocations and they didn't get converted when the direct I/O flushed the file because there was only enough space in the current AG to convert and write out the dirty pages within eof. Note that xfs_iomap_write_allocate() wont necessarily convert all the delayed allocation passed to it - it will return after allocating the first extent - so if the delayed allocation extends beyond eof then it will stay that way. SGI-PV: 983683 SGI-Modid: xfs-linux-melb:xfs-kern:31929a Signed-off-by: Lachlan McIlroy Signed-off-by: Christoph Hellwig --- diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c index f42f80a3b1..a44d68eb50 100644 --- a/fs/xfs/linux-2.6/xfs_aops.c +++ b/fs/xfs/linux-2.6/xfs_aops.c @@ -1338,6 +1338,10 @@ __xfs_get_blocks( offset = (xfs_off_t)iblock << inode->i_blkbits; ASSERT(bh_result->b_size >= (1 << inode->i_blkbits)); size = bh_result->b_size; + + if (!create && direct && offset >= i_size_read(inode)) + return 0; + error = xfs_iomap(XFS_I(inode), offset, size, create ? flags : BMAPI_READ, &iomap, &niomap); if (error)