Messages in this thread | | | Date | Tue, 20 Aug 2019 11:59:39 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH 2/2 v2] mm/zsmalloc.c: Fix race condition in zs_destroy_pool |
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On (08/09/19 11:17), Henry Burns wrote: > In zs_destroy_pool() we call flush_work(&pool->free_work). However, we > have no guarantee that migration isn't happening in the background > at that time. > > Since migration can't directly free pages, it relies on free_work > being scheduled to free the pages. But there's nothing preventing an > in-progress migrate from queuing the work *after* > zs_unregister_migration() has called flush_work(). Which would mean > pages still pointing at the inode when we free it. > > Since we know at destroy time all objects should be free, no new > migrations can come in (since zs_page_isolate() fails for fully-free > zspages). This means it is sufficient to track a "# isolated zspages" > count by class, and have the destroy logic ensure all such pages have > drained before proceeding. Keeping that state under the class > spinlock keeps the logic straightforward. > > Fixes: 48b4800a1c6a ("zsmalloc: page migration support") > Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+ Andrew
-ss
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