zram: deprecate zram attrs sysfs nodes

Add Documentation/ABI/obsolete/sysfs-block-zram file and list obsolete and
deprecated attributes there.  The patch also adds additional information
to zram documentation and describes the basic strategy:

- the existing RW nodes will be downgraded to WO nodes (in 4.11)
- deprecated RO sysfs nodes will eventually be removed (in 4.11)

Users will be additionally notified about deprecated attr usage by
pr_warn_once() (added to every deprecated attr _show()), as suggested by
Minchan Kim.

User space is advised to use zram<id>/stat, zram<id>/io_stat and
zram<id>/mm_stat files.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index c94a1a98e301..4491787095a0 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -43,11 +43,22 @@ static const char *default_compressor = "lzo";
 /* Module params (documentation at end) */
 static unsigned int num_devices = 1;
 
+static inline void deprecated_attr_warn(const char *name)
+{
+	pr_warn_once("%d (%s) Attribute %s (and others) will be removed. %s\n",
+			task_pid_nr(current),
+			current->comm,
+			name,
+			"See zram documentation.");
+}
+
 #define ZRAM_ATTR_RO(name)						\
 static ssize_t name##_show(struct device *d,		\
 				struct device_attribute *attr, char *b)	\
 {									\
 	struct zram *zram = dev_to_zram(d);				\
+									\
+	deprecated_attr_warn(__stringify(name));			\
 	return scnprintf(b, PAGE_SIZE, "%llu\n",			\
 		(u64)atomic64_read(&zram->stats.name));			\
 }									\
@@ -89,6 +100,7 @@ static ssize_t orig_data_size_show(struct device *dev,
 {
 	struct zram *zram = dev_to_zram(dev);
 
+	deprecated_attr_warn("orig_data_size");
 	return scnprintf(buf, PAGE_SIZE, "%llu\n",
 		(u64)(atomic64_read(&zram->stats.pages_stored)) << PAGE_SHIFT);
 }
@@ -99,6 +111,7 @@ static ssize_t mem_used_total_show(struct device *dev,
 	u64 val = 0;
 	struct zram *zram = dev_to_zram(dev);
 
+	deprecated_attr_warn("mem_used_total");
 	down_read(&zram->init_lock);
 	if (init_done(zram)) {
 		struct zram_meta *meta = zram->meta;
@@ -128,6 +141,7 @@ static ssize_t mem_limit_show(struct device *dev,
 	u64 val;
 	struct zram *zram = dev_to_zram(dev);
 
+	deprecated_attr_warn("mem_limit");
 	down_read(&zram->init_lock);
 	val = zram->limit_pages;
 	up_read(&zram->init_lock);
@@ -159,6 +173,7 @@ static ssize_t mem_used_max_show(struct device *dev,
 	u64 val = 0;
 	struct zram *zram = dev_to_zram(dev);
 
+	deprecated_attr_warn("mem_used_max");
 	down_read(&zram->init_lock);
 	if (init_done(zram))
 		val = atomic_long_read(&zram->stats.max_used_pages);