From: Sergey Senozhatsky Date: Wed, 11 Mar 2026 08:42:44 +0000 (+0900) Subject: zram: do not permit params change after init X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=241f9005b1c81c2637eef2c836a03c83b4f3eeb9;p=thirdparty%2Flinux.git zram: do not permit params change after init Patch series "zram: recompression cleanups and tweaks", v2. This series is a somewhat random mix of fixups, recompression cleanups and improvements partly based on internal conversations. A few patches in the series remove unexpected or confusing behaviour, e.g. auto correction of bad priority= param for recompression, which should have always been just an error. Then it also removes "chain recompression" which has a tricky, unexpected and confusing behaviour at times. We also unify and harden the handling of algo/priority params. There is also an addition of missing device lock in algorithm_params_store() which previously permitted modification of algo params while the device is active. This patch (of 6): First, algorithm_params_store(), like any sysfs handler, should grab device lock. Second, like any write() sysfs handler, it should grab device lock in exclusive mode. Third, it should not permit change of algos' parameters after device init, as this doesn't make sense - we cannot compress with one C/D dict and then just change C/D dict to a different one, for example. Another thing to notice is that algorithm_params_store() accesses device's ->comp_algs for algo priority lookup, which should be protected by device lock in exclusive mode in general. Link: https://lkml.kernel.org/r/20260311084312.1766036-1-senozhatsky@chromium.org Link: https://lkml.kernel.org/r/20260311084312.1766036-2-senozhatsky@chromium.org Fixes: 4eac932103a5 ("zram: introduce algorithm_params device attribute") Signed-off-by: Sergey Senozhatsky Acked-by: Brian Geffon Cc: gao xu Cc: Jens Axboe Cc: Minchan Kim Signed-off-by: Andrew Morton --- diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 990d391847f4c..bc5777b245d4f 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1734,6 +1734,10 @@ static ssize_t algorithm_params_store(struct device *dev, } } + guard(rwsem_write)(&zram->dev_lock); + if (init_done(zram)) + return -EBUSY; + /* Lookup priority by algorithm name */ if (algo) { s32 p;