zram: return error-valued pointer from zcomp_create()

Instead of returning just NULL, return ERR_PTR from zcomp_create() if
compressing backend creation has failed.  ERR_PTR(-EINVAL) for unsupported
compression algorithm request, ERR_PTR(-ENOMEM) for allocation (zcomp or
compression stream) error.

Perform IS_ERR() check of returned from zcomp_create() value in
disksize_store() and set return code to PTR_ERR().

Change suggested by Jerome Marchand.

[akpm@linux-foundation.org: clean up error recovery flow]
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Jerome Marchand <jmarchan@redhat.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 6 deletions

diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
index d5919031ca8b..5647d8fe1dc1 100644
--- a/drivers/block/zram/zcomp.c
+++ b/drivers/block/zram/zcomp.c
@@ -9,6 +9,7 @@
 
 #include <linux/kernel.h>
 #include <linux/string.h>
+#include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/wait.h>
 #include <linux/sched.h>
@@ -319,9 +320,10 @@ void zcomp_destroy(struct zcomp *comp)
 
 /*
  * search available compressors for requested algorithm.
- * allocate new zcomp and initialize it. return NULL
- * if requested algorithm is not supported or in case
- * of init error
+ * allocate new zcomp and initialize it. return compressing
+ * backend pointer or ERR_PTR if things went bad. ERR_PTR(-EINVAL)
+ * if requested algorithm is not supported, ERR_PTR(-ENOMEM) in
+ * case of allocation error.
  */
 struct zcomp *zcomp_create(const char *compress, int max_strm)
 {
@@ -330,11 +332,11 @@ struct zcomp *zcomp_create(const char *compress, int max_strm)
 
         backend = find_backend(compress);
         if (!backend)
-                return NULL;
+                return ERR_PTR(-EINVAL);
 
         comp = kzalloc(sizeof(struct zcomp), GFP_KERNEL);
         if (!comp)
-                return NULL;
+                return ERR_PTR(-ENOMEM);
 
         comp->backend = backend;
         if (max_strm > 1)
@@ -343,7 +345,7 @@ struct zcomp *zcomp_create(const char *compress, int max_strm)
                 zcomp_strm_single_create(comp);
         if (!comp->stream) {
                 kfree(comp);
-                return NULL;
+                return ERR_PTR(-ENOMEM);
         }
         return comp;
 }