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Btrfs: hold a ref on the inode during writepages

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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>
This commit is contained in:
Josef Bacik 2012-06-27 17:18:41 -04:00 committed by Chris Mason
parent bdb7d303b3
commit 7fd1a3f73f
1 changed files with 14 additions and 0 deletions
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14
fs/btrfs/extent_io.c
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@ -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;
}