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btrfs: fix the memory leak caused in lzo_compress_pages()

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[BUG]
Fstests generic/027 is pretty easy to trigger a slow but steady memory
leak if run with "-o compress=lzo" mount option.

Normally one single run of generic/027 is enough to eat up at least 4G ram.

[CAUSE]
In commit d4088803f5 ("btrfs: subpage: make lzo_compress_pages()
compatible") we changed how @page_in is released.

But that refactoring makes @page_in only released after all pages being
compressed.

This leaves error path not releasing @page_in. And by "error path"
things like incompressible data will also be treated as an error
(-E2BIG).

Thus it can cause a memory leak if even nothing wrong happened.

[FIX]
Add check under @out label to release @page_in when needed, so when we
hit any error, the input page is properly released.

Reported-by: Josef Bacik <josef@toxicpanda.com>
Fixes: d4088803f5 ("btrfs: subpage: make lzo_compress_pages() compatible")
Reviewed-and-tested-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2021-11-20 16:34:11 +08:00 committed by David Sterba
parent 6c405b2409
commit daf87e9535
1 changed files with 2 additions and 0 deletions
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2
fs/btrfs/lzo.c
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@ -276,6 +276,8 @@ int lzo_compress_pages(struct list_head *ws, struct address_space *mapping,
*total_out = cur_out;
*total_in = cur_in - start;
out:
if (page_in)
put_page(page_in);
*out_pages = DIV_ROUND_UP(cur_out, PAGE_SIZE);
return ret;
}