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b=r5qRRodoitaTjP8Oo49cX59bM6/ww2hHBYTb3Av7xMXj+588xDmtzRecYNetDNhFv ai9zk9r3Xzm18NmIbze5e3mQ2pBeKPP8CBLcEfQ/N5+/scOR45Ef7gyJWDMnT7u5Z+ RzEd/KqSZq1jO6EgQgwz7TBgc6fpsdBNYnR1aL2lCc/jLP8tAT8VBpMHJulGGAp5LZ dQce4oSOE8yWWuFcdMJX40dA9YUhBlWywlFBBlJx31GKOj6nd834tJWVU2bvwaEvgp PLopseWmR8aLG34tjuSZXAIjmkR9+ib6/8rC7VS+7wI6qRKK2Ap2SZvRO3aYaqzly/ a9BqyaBLojGLg== Date: Thu, 19 Mar 2026 10:59:55 -0700 From: Minchan Kim To: Sergey Senozhatsky Cc: Andrew Morton , Brian Geffon , Richard Chang , linux-block@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] zram: do not slot_free() written-back slots Message-ID: References: <20260319034912.1894770-1-senozhatsky@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Stat-Signature: cqxduxqdfn8qsk5xwdrfqnrhw4n5675m X-Rspamd-Queue-Id: B3141100016 X-Rspamd-Server: rspam03 X-HE-Tag: 1773943197-183042 X-HE-Meta: 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 cfnfVESB 1HL8NMaBFlwytSAfdubJ5FtAo8k6U5iNBvxtqxwnwK/s3HARaoJrCIXode7dcA65rx1mOOSrO0q5ch/JXjzjzs8o2heZhDDfZihCsg7MQK5ozya2sGUFhvt8br0rRMdobKSgnP25+ckSDGaulWLpFLL4vEiaBWQvRXbLpuQZ/Te5H/OF8QLWJ8TBfdoBkn20QSltJN+d7AhHEbyu7brIb4w4OOyxxFswD2RIvybV9k8iHVudITE9CxtcJcMGRvtyJLqWBmylNy1nqZ0eE/e/ABckYOANBuJE5G2qWIotu5mSRX2jcRbwuC17pLpI3m7/50rDpPEn/alzw+SE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Mar 19, 2026 at 01:05:55PM +0900, Sergey Senozhatsky wrote: > As a side note: > > On (26/03/19 12:44), Sergey Senozhatsky wrote: > > - slot_free(zram, index); > [..] > > - if (huge) > > - set_slot_flag(zram, index, ZRAM_HUGE); > > Original code had a bug. slot_free() would decrement ->huge_pages, > then writeback completion would restore the HUGE flag, so when slot > would get freed for real slot_free() would decrement ->huge_pages > again, leading to underflow. This should also go into description of the patch.