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authorLachlan McIlroy <lachlan@sgi.com>2008-09-17 06:50:14 (GMT)
committerLachlan McIlroy <lachlan@redback.melbourne.sgi.com>2008-09-17 06:50:14 (GMT)
commit364f358a734ddcd827c662ccbfa58ee3ac510762 (patch)
tree2af362aa418b145e0626066ed2c8b3b0918630eb /fs/xfs
parent6efdf281777eb07fac28ac2b2d7df1e619ee6da1 (diff)
downloadlinux-364f358a734ddcd827c662ccbfa58ee3ac510762.tar.xz
[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 <lachlan@sgi.com> Signed-off-by: Christoph Hellwig <hch@infradead.org>
Diffstat (limited to 'fs/xfs')
-rw-r--r--fs/xfs/linux-2.6/xfs_aops.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index f42f80a..a44d68e 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)