linux-kernel - Re: [PATCH] zram: pass buffer offset to zcomp_available

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Message-ID: <tgqiahkbc6u6w75rivbishixxq64wfzx6tucscaa3yyt5u55kc@ur62ahdhq4ew>
Date: Fri, 4 Jul 2025 10:53:47 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Jens Axboe <axboe@...nel.dk>
Cc: Minchan Kim <minchan@...nel.org>, Rahul Kumar <rk0006818@...il.com>, 
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCH] zram: pass buffer offset to zcomp_available_show()

On (25/06/27 16:18), Sergey Senozhatsky wrote:
> In most cases zcomp_available_show() is the only emitting
> function that is called from sysfs read() handler, so it
> assumes that there is a whole PAGE_SIZE buffer to work with.
> There is an exception, however: recomp_algorithm_show().
> 
> In recomp_algorithm_show() we prepend the buffer with
> priority number before we pass it to zcomp_available_show(),
> so it cannot assume PAGE_SIZE anymore and must take
> recomp_algorithm_show() modifications into consideration.
> Therefore we need to pass buffer offset to zcomp_available_show().
> 
> Also convert it to use sysfs_emit_at(), to stay aligned
> with the rest of zram's sysfs read() handlers.
> 
> On practice we are never even close to using the whole PAGE_SIZE
> buffer, so that's not a critical bug, but still.

Jens, do you feel like picking these 2 up or should I route
them to Andrew's tree?