zram: move comp allocation out of init_lock

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

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Minchan Kim <minchan@kernel.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 15 insertions, 12 deletions

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 15d46f2e158c..e4d536b485e6 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;
 }