Messages in this thread Patch in this message | | | From | Sergey Senozhatsky <> | Subject | [PATCH 2/2] zram: introduce automatic device_id generation | Date | Wed, 4 Mar 2015 23:16:41 +0900 |
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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@gmail.com> --- 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 --git a/Documentation/ABI/testing/sysfs-class-zram b/Documentation/ABI/testing/sysfs-class-zram index 99b2a1e..0b678b2 100644 --- a/Documentation/ABI/testing/sysfs-class-zram +++ b/Documentation/ABI/testing/sysfs-class-zram @@ -11,8 +11,11 @@ Date: March 2015 KernelVersion: 4.1 Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> 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 --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 4b140fa..6bbdded 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -112,6 +112,16 @@ To remove the existing /dev/zramX device (where X is a device id) 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 --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 0978307..e0b40bb 100644 --- a/drivers/block/zram/zram_drv.c +++ b/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; @@ -1267,6 +1274,24 @@ static ssize_t zram_add_store(struct class *class, 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, @@ -1278,7 +1303,7 @@ static ssize_t zram_remove_store(struct class *class, } static struct class_attribute zram_control_class_attrs[] = { - __ATTR_WO(zram_add), + __ATTR_RW(zram_add), __ATTR_WO(zram_remove), __ATTR_NULL, }; -- 2.3.1.167.g7f4ba4b
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