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Ts'o" , Jens Axboe , Ext4 Developers List , "linux-kernel@vger.kernel.org" , linux-block , Linux-MM , Roman Gushchin , Andrew Morton , Johannes Weiner , Vlastimil Babka Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Sep 25, 2020 at 10:17 AM Linus Torvalds wrote: > > On Fri, Sep 25, 2020 at 9:19 AM Ming Lei wrote: > > > > git bisect shows the first bad commit: > > > > [10befea91b61c4e2c2d1df06a2e978d182fcf792] mm: memcg/slab: use a single set of > > kmem_caches for all allocations > > > > And I have double checked that the above commit is really the first bad > > commit for the list corruption issue of 'list_del corruption, ffffe1c241b00408->next > > is LIST_POISON1 (dead000000000100)', > > Thet commit doesn't revert cleanly, but I think that's purely because > we'd also need to revert > > 849504809f86 ("mm: memcg/slab: remove unused argument by charge_slab_page()") > 74d555bed5d0 ("mm: slab: rename (un)charge_slab_page() to > (un)account_slab_page()") > > too. > > Can you verify that a > > git revert 74d555bed5d0 849504809f86 10befea91b61 > > on top of current -git makes things work for you again? > > I'm going to do an rc8 this release simply because we have another VM > issue that I hope to get fixed - but there we know what the problem > and the fix _is_, it just needs some care. > > So if Roman (or somebody else) can see what's wrong and we can fix > this quickly, we don't need to go down the revert path, but .. > I think I have a theory. The issue is happening due to the potential infinite recursion: [ 5060.124412] ___cache_free+0x488/0x6b0 *****Second recursion [ 5060.128666] kfree+0xc9/0x1d0 [ 5060.131947] kmem_freepages+0xa0/0xf0 [ 5060.135746] slab_destroy+0x19/0x50 [ 5060.139577] slabs_destroy+0x6d/0x90 [ 5060.143379] ___cache_free+0x4a3/0x6b0 *****First recursion [ 5060.147896] kfree+0xc9/0x1d0 [ 5060.151082] kmem_freepages+0xa0/0xf0 [ 5060.155121] slab_destroy+0x19/0x50 [ 5060.159028] slabs_destroy+0x6d/0x90 [ 5060.162920] ___cache_free+0x4a3/0x6b0 [ 5060.167097] kfree+0xc9/0x1d0 ___cache_free() is calling cache_flusharray() to flush the local cpu array_cache if the cache has more elements than the limit (ac->avail >= ac->limit). cache_flusharray() is removing batchcount number of element from local cpu array_cache and pass it slabs_destroy (if the node shared cache is also full). Note that we have not updated local cpu array_cache size yet and called slabs_destroy() which can call kfree() through unaccount_slab_page(). We are on the same CPU and this recursive kfree again check the (ac->avail >= ac->limit) and call cache_flusharray() again and recurse indefinitely.