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Subject[PATCH] zram: move comp allocation out of init_lock
Date
While fixing lockdep spew of ->init_lock reported by Sasha Levin [1], Minchan
Kim noted [2] that it's better to move compression backend allocation (using
GPF_KERNEL) out of the ->init_lock lock, same way as with zram_meta_alloc(),
in order to prevent the same lockdep spew.

[1] https://lkml.org/lkml/2014/2/27/337
[2] https://lkml.org/lkml/2014/3/3/32

Cc: Sasha Levin <sasha.levin@oracle.com>
Reported-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
drivers/block/zram/zram_drv.c | 27 +++++++++++++++------------
1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 15d46f2..e4d536b 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -580,9 +580,10 @@ static ssize_t disksize_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t len)
{
u64 disksize;
+ struct zcomp *comp;
struct zram_meta *meta;
struct zram *zram = dev_to_zram(dev);
- int err;
+ int err = -EINVAL;

disksize = memparse(buf, NULL);
if (!disksize)
@@ -593,30 +594,32 @@ static ssize_t disksize_store(struct device *dev,
if (!meta)
return -ENOMEM;

+ comp = zcomp_create(zram->compressor, zram->max_comp_streams);
+ if (!comp) {
+ pr_info("Cannot initialise %s compressing backend\n",
+ zram->compressor);
+ goto out_cleanup;
+ }
+
down_write(&zram->init_lock);
if (init_done(zram)) {
+ up_write(&zram->init_lock);
pr_info("Cannot change disksize for initialized device\n");
err = -EBUSY;
- goto out_free_meta;
- }
-
- zram->comp = zcomp_create(zram->compressor, zram->max_comp_streams);
- if (!zram->comp) {
- pr_info("Cannot initialise %s compressing backend\n",
- zram->compressor);
- err = -EINVAL;
- goto out_free_meta;
+ goto out_cleanup;
}

zram->meta = meta;
+ zram->comp = comp;
zram->disksize = disksize;
set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
up_write(&zram->init_lock);

return len;

-out_free_meta:
- up_write(&zram->init_lock);
+out_cleanup:
+ if (comp)
+ zcomp_destroy(comp);
zram_meta_free(meta);
return err;
}
--
1.9.0.382.g7f3562c


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