Messages in this thread | | | From | Weijie Yang <> | Subject | [PATCH v2 0/4] mm/zswap bugfix: memory leaks and other problems | Date | Fri, 06 Sep 2013 13:15:08 +0800 |
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This patch series fix a few bugs in zswap based on Linux-3.11.
v1 --> v2 - free memory in zswap_frontswap_invalidate_area (in patch 1) - fix whitespace corruption (line wrapping)
Corresponding mail thread: https://lkml.org/lkml/2013/8/18/59
These issues fixed/optimized are:
1. memory leaks when re-swapon
2. memory leaks when invalidate and reclaim occur concurrently
3. avoid unnecessary page scanning
4. use GFP_NOIO instead of GFP_KERNEL to avoid zswap store and reclaim functions called recursively
Issues discussed in that mail thread NOT fixed as it happens rarely or not a big problem:
1. a "theoretical race condition" when reclaim page When a handle alloced from zbud, zbud considers this handle is used validly by upper(zswap) and can be a candidate for reclaim. But zswap has to initialize it such as setting swapentry and adding it to rbtree. so there is a race condition, such as: thread 0: obtain handle x from zbud_alloc thread 1: zbud_reclaim_page is called thread 1: callback zswap_writeback_entry to reclaim handle x thread 1: get swpentry from handle x (it is random value now) thread 1: bad thing may happen thread 0: initialize handle x with swapentry
2. frontswap_map bitmap not cleared after zswap reclaim Frontswap uses frontswap_map bitmap to track page in "backend" implementation, when zswap reclaim a page, the corresponding bitmap record is not cleared.
mm/zswap.c | 34 +++++++++++++++++++++++----------- 1 file changed, 23 insertions(+), 11 deletions(-)
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