From: Dave Chinner <dchinner@xxxxxxxxxx>
There is an assumption in the parts of XFS that flushing a dirty
file will make all the delayed allocation blocks disappear from an
inode. That is, that after calling xfs_flush_pages() then
ip->i_delayed_blks will be zero.
This is an invalid assumption as we may have specualtive
preallocation beyond EOF and they are recorded in
ip->i_delayed_blks. A flush of the dirty pages of an inode will not
change the state of these blocks beyond EOF, so a non-zero
deeelalloc block count after a flush is valid.
The bmap code has an invalid ASSERT() that needs to be removed, and
the swapext code has a bug in that while it swaps the data forks
around, it fails to swap the i_delayed_blks counter associated with
the fork and hence can get the block accounting wrong.
Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
fs/xfs/xfs_bmap.c | 9 +++++++--
fs/xfs/xfs_dfrag.c | 13 +++++++++++++
2 files changed, 20 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index 08b179f..4111cd3 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/fs/xfs/xfs_bmap.c
@@ -5471,8 +5471,13 @@ xfs_getbmap(
if (error)
goto out_unlock_iolock;
}
-
- ASSERT(ip->i_delayed_blks == 0);
+ /*
+ * even after flushing the inode, there can still be delalloc
+ * blocks on the inode beyond EOF due to speculative
+ * preallocation. These are not removed until the release
+ * function is called or the inode is inactivated. Hence we
+ * cannot assert here that ip->i_delayed_blks == 0.
+ */
}
lock = xfs_ilock_map_shared(ip);
diff --git a/fs/xfs/xfs_dfrag.c b/fs/xfs/xfs_dfrag.c
index 3b9582c..e60490b 100644
--- a/fs/xfs/xfs_dfrag.c
+++ b/fs/xfs/xfs_dfrag.c
@@ -377,6 +377,19 @@ xfs_swap_extents(
ip->i_d.di_format = tip->i_d.di_format;
tip->i_d.di_format = tmp;
+ /*
+ * The extents in the source inode could still contain speculative
+ * preallocation beyond EOF (e.g. the file is open but not modified
+ * while defrag is in progress). In that case, we need to copy over the
+ * number of delalloc blocks the data fork in the source inode is
+ * tracking beyond EOF so that when the fork is truncated away when the
+ * temporary inode is unlinked we don't underrun the i_delayed_blks
+ * counter on that inode.
+ */
+ ASSERT(tip->i_delayed_blks == 0);
+ tip->i_delayed_blks = ip->i_delayed_blks;
+ ip->i_delayed_blks = 0;
+
ilf_fields = XFS_ILOG_CORE;
switch(ip->i_d.di_format) {
--
1.7.2.3
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