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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82ca85fc735sm9245251b3a.40.2026.03.31.00.32.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 31 Mar 2026 00:32:54 -0700 (PDT) Message-ID: Date: Tue, 31 Mar 2026 18:02:47 +1030 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] zram: do not forget to endio for partial discard requests To: Sergey Senozhatsky , Andrew Morton Cc: Minchan Kim , Brian Geffon , linux-block@vger.kernel.org, linux-mm@kvack.org, Christoph Hellwig References: <20260331071537.706139-1-senozhatsky@chromium.org> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: <20260331071537.706139-1-senozhatsky@chromium.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 75521C000D X-Stat-Signature: akye9yrq3ba59xbhd3kp4arcgao3o4wc X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1774942377-370043 X-HE-Meta: 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 w6Q01n7R 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2026/3/31 17:45, Sergey Senozhatsky 写道: > As reported by Qu Wenruo, the following > > getconf PAGESIZE > 65536 > blkdiscard -p 4k /dev/zram0 > > takes literally forever to complete. zram doesn't support > partial discards and just returns immediately w/o doing any > discard work in such cases. The problem is that we forget > to endio on our way out, so blkdiscard sleeps forever in > submit_bio_wait(). Fix this by adding a missing bio_endio() > call. > > Fixes: 0120dd6e4e202 ("zram: make zram_bio_discard more self-contained") > Signed-off-by: Sergey Senozhatsky > Reported-by: Qu Wenruo > Closes: https://lore.kernel.org/linux-block/92361cd3-fb8b-482e-bc89-15ff1acb9a59@suse.com > Cc: Christoph Hellwig Test-by: Qu Wenruo Now all discard related works like mkfs.btrfs and mounting btrfs with async discard on zram devices works fine. Thanks a lot for such a quick debugging and fix! Although I'm still seeing not ideal performance if a btrfs with 4K block size on that zram device. On a regular block device (LVM): # mkfs.btrfs -f /dev/test/scratch1 # mount /dev/test/scratch1 /mnt/btrfs # time sudo ./xfstests-dev/ltp/fsstress -d /mnt/btrfs/ -n 10000 \ -s 1774231493 -w real 0m3.435s user 0m0.005s sys 0m0.009s On a zram block device: (mkfs.btrfs defaults to 4K block size) # mkfs.btrfs -f /dev/zram0 # mount /dev/test/scratch1 /mnt/btrfs # time sudo ./xfstests-dev/ltp/fsstress -d /mnt/btrfs/ -n 10000 \ -s 1774231493 -w real 0m10.726s user 0m0.005s sys 0m0.009s Which is 3 times slower than regular block devices. And after that short fsstress run: NAME ALGORITHM DISKSIZE DATA COMPR TOTAL STREAMS MOUNTPOINT /dev/zram0 zstd 1G 271.2M 10M 20.4M I guess this time the overhead is just in the compression so that's something expected? Thanks, Qu > --- > drivers/block/zram/zram_drv.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > index dcea703a6766..b0637423953b 100644 > --- a/drivers/block/zram/zram_drv.c > +++ b/drivers/block/zram/zram_drv.c > @@ -2683,8 +2683,10 @@ static void zram_bio_discard(struct zram *zram, struct bio *bio) > * skipping this logical block is appropriate here. > */ > if (offset) { > - if (n <= (PAGE_SIZE - offset)) > + if (n <= (PAGE_SIZE - offset)) { > + bio_endio(bio); > return; > + } > > n -= (PAGE_SIZE - offset); > index++;