Btrfs: hold a ref on the inode during writepages (7fd1a3f7) · Commits · 戴 / test

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 −0

Original line number	Diff line number	Diff line
		@@ -3324,6 +3324,7 @@ 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;
		@@ -3334,6 +3335,18 @@ 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 */
		@@ -3428,6 +3441,7 @@ retry:
		index = 0;
		goto retry;
		}
		btrfs_add_delayed_iput(inode);
		return ret;
		}

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