Josef Bacik
2012-Jun-27 21:20 UTC
[PATCH] Btrfs: hold a ref on the inode during writepages
We can race with unlink and not actually be able to do our igrab in
btrfs_add_ordered_extent. This will result in all sorts of problems.
Instead of doing the complicated work to try and handle returning an error
properly from btrfs_add_ordered_extent, just hold a ref to the inode during
writepages. If we cannot grab a ref we know we''re freeing this inode
anyway
and can just drop the dirty pages on the floor, because screw them
we''re
going to invalidate them anyway. Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
---
fs/btrfs/extent_io.c | 14 ++++++++++++++
1 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 8e9dea7..190e5b6 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3638,6 +3638,7 @@ static int extent_write_cache_pages(struct extent_io_tree
*tree,
writepage_t writepage, void *data,
void (*flush_fn)(void *))
{
+ struct inode *inode = mapping->host;
int ret = 0;
int done = 0;
int nr_to_write_done = 0;
@@ -3648,6 +3649,18 @@ static int extent_write_cache_pages(struct extent_io_tree
*tree,
int scanned = 0;
int tag;
+ /*
+ * We have to hold onto the inode so that ordered extents can do their
+ * work when the IO finishes. The alternative to this is failing to add
+ * an ordered extent if the igrab() fails there and that is a huge pain
+ * to deal with, so instead just hold onto the inode throughout the
+ * writepages operation. If it fails here we are freeing up the inode
+ * anyway and we''d rather not waste our time writing out stuff that
is
+ * going to be truncated anyway.
+ */
+ if (!igrab(inode))
+ return 0;
+
pagevec_init(&pvec, 0);
if (wbc->range_cyclic) {
index = mapping->writeback_index; /* Start from prev offset */
@@ -3742,6 +3755,7 @@ retry:
index = 0;
goto retry;
}
+ btrfs_add_delayed_iput(inode);
return ret;
}
--
1.7.7.6
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