The patch titled
Subject: zram: introduce automatic device_id generation
has been added to the -mm tree. Its filename is
zram-introduce-automatic-device_id-generation.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/zram-introduce-automatic-device_id-generation.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/zram-introduce-automatic-device_id-generation.patch
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------------------------------------------------------
From: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Subject: zram: introduce automatic device_id generation
The existing device creation interface requires user to provide new and
unique device_id for every device being created. This might be difficult
to handle (f.e. in automated scripts).
Extend zram-control/zram_add interface to support read and write
operations. Write operation remains the same:
echo X > /sys/class/zram-control/zram_add
will add /dev/zramX (or return error).
Read operation is treated as 'pick up available device_id, add new device
and return device_id'.
Example:
cat /sys/class/zram-control/zram_add
2
cat /sys/class/zram-control/zram_add
3
so user-space can proceed with /dev/zram2, /dev/zram3 init and usage.
An attempt to use already used device_id (-EEXIST)
echo 3 > /sys/class/zram-control/zram_add
-bash: echo: write error: File exists
Returning zram_add error code back to user (-ENOMEM in this case)
cat /sys/class/zram-control/zram_add
cat: /sys/class/zram-control/zram_add: Cannot allocate memory
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/ABI/testing/sysfs-class-zram | 7 +++-
Documentation/blockdev/zram.txt | 10 ++++++
drivers/block/zram/zram_drv.c | 31 +++++++++++++++++--
3 files changed, 43 insertions(+), 5 deletions(-)
diff -puN Documentation/ABI/testing/sysfs-class-zram~zram-introduce-automatic-device_id-generation Documentation/ABI/testing/sysfs-class-zram
--- a/Documentation/ABI/testing/sysfs-class-zram~zram-introduce-automatic-device_id-generation
+++ a/Documentation/ABI/testing/sysfs-class-zram
@@ -11,8 +11,11 @@ Date: March 2015
KernelVersion: 4.1
Contact: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Description:
- Add a specific /dev/zramX device, where X is a device_id
- provided by user
+ RW attribuite. Write operation adds a specific /dev/zramX
+ device, where X is a device_id provided by user.
+ Read operation will automatically pick up avilable device_id
+ X, add /dev/zramX device and return that device_id X back to
+ user.
What: /sys/class/zram-control/zram_add
Date: March 2015
diff -puN Documentation/blockdev/zram.txt~zram-introduce-automatic-device_id-generation Documentation/blockdev/zram.txt
--- a/Documentation/blockdev/zram.txt~zram-introduce-automatic-device_id-generation
+++ a/Documentation/blockdev/zram.txt
@@ -112,6 +112,16 @@ To remove the existing /dev/zramX device
execute
echo X > /sys/class/zram-control/zram_remove
+Additionally, zram also handles automatic device_id generation and assignment.
+
+ cat /sys/class/zram-control/zram_add
+ 1
+ cat /sys/class/zram-control/zram_add
+ 2
+
+this will pick up available device_id X, add corresponding /dev/zramX
+device and return its device_id X back to user (or error code).
+
8) Stats:
Per-device statistics are exported as various nodes under
/sys/block/zram<id>/
diff -puN drivers/block/zram/zram_drv.c~zram-introduce-automatic-device_id-generation drivers/block/zram/zram_drv.c
--- a/drivers/block/zram/zram_drv.c~zram-introduce-automatic-device_id-generation
+++ a/drivers/block/zram/zram_drv.c
@@ -1078,8 +1078,15 @@ static int zram_add(int device_id)
if (!zram)
return ret;
- ret = idr_alloc(&zram_index_idr, zram, device_id,
- device_id + 1, GFP_KERNEL);
+ if (device_id < 0) {
+ /* generate new device_id */
+ ret = idr_alloc(&zram_index_idr, zram, 0, 0, GFP_KERNEL);
+ device_id = ret;
+ } else {
+ /* use provided device_id */
+ ret = idr_alloc(&zram_index_idr, zram, device_id,
+ device_id + 1, GFP_KERNEL);
+ }
if (ret < 0)
goto out_free_dev;
@@ -1271,6 +1278,24 @@ static ssize_t zram_add_store(struct cla
return ret ? ret : count;
}
+static ssize_t zram_add_show(struct class *class,
+ struct class_attribute *attr,
+ char *buf)
+{
+ int ret;
+
+ mutex_lock(&zram_index_mutex);
+ /* read operation on zram_add is - pick up device_id
+ * automatically, add corresponding device and return
+ * that device_id back to user */
+ ret = zram_add(-1);
+ mutex_unlock(&zram_index_mutex);
+
+ if (ret < 0)
+ return ret;
+ return scnprintf(buf, PAGE_SIZE, "%d\n", ret);
+}
+
static ssize_t zram_remove_store(struct class *class,
struct class_attribute *attr,
const char *buf,
@@ -1282,7 +1307,7 @@ static ssize_t zram_remove_store(struct
}
static struct class_attribute zram_control_class_attrs[] = {
- __ATTR_WO(zram_add),
+ __ATTR_RW(zram_add),
__ATTR_WO(zram_remove),
__ATTR_NULL,
};
_
Patches currently in -mm which might be from sergey.senozhatsky@xxxxxxxxx are
zram-cosmetic-zram_attr_ro-code-formatting-tweak.patch
zram-use-idr-instead-of-zram_devices-array.patch
zram-factor-out-device-reset-from-reset_store.patch
zram-reorganize-code-layout.patch
zram-add-dynamic-device-add-remove-functionality.patch
zram-add-dynamic-device-add-remove-functionality-fix.patch
zram-remove-max_num_devices-limitation.patch
zram-report-every-added-and-removed-device.patch
zram-trivial-correct-flag-operations-comment.patch
zram-return-zram-device_id-value-from-zram_add.patch
zram-introduce-automatic-device_id-generation.patch
zram-introduce-automatic-device_id-generation-fix.patch
zsmalloc-decouple-handle-and-object.patch
zsmalloc-factor-out-obj_.patch
zsmalloc-support-compaction.patch
zsmalloc-adjust-zs_almost_full.patch
zram-support-compaction.patch
zsmalloc-record-handle-in-page-private-for-huge-object.patch
zsmalloc-add-fullness-into-stat.patch
cpumask-dont-perform-while-loop-in-cpumask_next_and.patch
lib-lz4-pull-out-constant-tables.patch
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