Re: [PATCH] btrfs: fix the memory leak caused in lzo_compress_pages()

[Josef Bacik <josef@toxicpanda.com>]

On Sat, Nov 20, 2021 at 04:34:11PM +0800, Qu Wenruo wrote:
> [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 d4088803f511 ("btrfs: subpage: make lzo_compress_pages()
> compatible") we changed how @page_in is released.
> 
> But that refactor 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 leave btrfs to leak memory even there is 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: d4088803f511 ("btrfs: subpage: make lzo_compress_pages() compatible")
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Woo now we're making it all the way through the xfstests runs on the vm that has
-o compress=lzo.  You can add

Reviewed-and-tested-by: Josef Bacik <josef@toxicpanda.com>

Thanks for digging into this Qu,

Josef