Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753097Ab0HIR05 (ORCPT ); Mon, 9 Aug 2010 13:26:57 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:60296 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752933Ab0HIR0w (ORCPT ); Mon, 9 Aug 2010 13:26:52 -0400 From: Nitin Gupta To: Pekka Enberg , Minchan Kim , Andrew Morton , Greg KH Cc: Linux Driver Project , linux-mm , linux-kernel Subject: [PATCH 02/10] Remove need for explicit device initialization Date: Mon, 9 Aug 2010 22:56:48 +0530 Message-Id: <1281374816-904-3-git-send-email-ngupta@vflare.org> X-Mailer: git-send-email 1.7.2.1 In-Reply-To: <1281374816-904-1-git-send-email-ngupta@vflare.org> References: <1281374816-904-1-git-send-email-ngupta@vflare.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6084 Lines: 205 Currently, the user has to explicitly write a positive value to initstate sysfs node before the device can be used. This event triggers allocation of per-device metadata like memory pool, table array and so on. We do not pre-initialize all zram devices since the 'table' array, mapping disk blocks to compressed chunks, takes considerable amount of memory (8 bytes per page). So, pre-initializing all devices will be quite wasteful if only few or none of the devices are actually used. This explicit device initialization from user is an odd requirement and can be easily avoided. We now initialize the device when first write is done to the device. Signed-off-by: Nitin Gupta --- drivers/staging/zram/zram_drv.c | 35 +++++++++++++++++++++++------------ drivers/staging/zram/zram_drv.h | 2 ++ drivers/staging/zram/zram_sysfs.c | 26 ++++---------------------- 3 files changed, 29 insertions(+), 34 deletions(-) diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c index 3f698a5..c5f84ee 100644 --- a/drivers/staging/zram/zram_drv.c +++ b/drivers/staging/zram/zram_drv.c @@ -207,9 +207,15 @@ static int zram_read(struct zram *zram, struct bio *bio) u32 index; struct bio_vec *bvec; - zram_stat64_inc(zram, &zram->stats.num_reads); + if (unlikely(!zram->init_done)) { + set_bit(BIO_UPTODATE, &bio->bi_flags); + bio_endio(bio, 0); + return 0; + } + zram_stat64_inc(zram, &zram->stats.num_reads); index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT; + bio_for_each_segment(bvec, bio, i) { int ret; size_t clen; @@ -275,16 +281,20 @@ out: static int zram_write(struct zram *zram, struct bio *bio) { - int i; + int i, ret; u32 index; struct bio_vec *bvec; - zram_stat64_inc(zram, &zram->stats.num_writes); + if (unlikely(!zram->init_done)) { + ret = zram_init_device(zram); + if (ret) + goto out; + } + zram_stat64_inc(zram, &zram->stats.num_writes); index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT; bio_for_each_segment(bvec, bio, i) { - int ret; u32 offset; size_t clen; struct zobj_header *zheader; @@ -425,11 +435,6 @@ static int zram_make_request(struct request_queue *queue, struct bio *bio) int ret = 0; struct zram *zram = queue->queuedata; - if (unlikely(!zram->init_done)) { - bio_io_error(bio); - return 0; - } - if (!valid_io_request(zram, bio)) { zram_stat64_inc(zram, &zram->stats.invalid_io); bio_io_error(bio); @@ -453,7 +458,7 @@ void zram_reset_device(struct zram *zram) { size_t index; - /* Do not accept any new I/O request */ + mutex_lock(&zram->init_lock); zram->init_done = 0; /* Free various per-device buffers */ @@ -490,6 +495,7 @@ void zram_reset_device(struct zram *zram) memset(&zram->stats, 0, sizeof(zram->stats)); zram->disksize = 0; + mutex_unlock(&zram->init_lock); } int zram_init_device(struct zram *zram) @@ -497,9 +503,11 @@ int zram_init_device(struct zram *zram) int ret; size_t num_pages; + mutex_lock(&zram->init_lock); + if (zram->init_done) { - pr_info("Device already initialized!\n"); - return -EBUSY; + mutex_unlock(&zram->init_lock); + return 0; } zram_set_disksize(zram, totalram_pages << PAGE_SHIFT); @@ -542,11 +550,13 @@ int zram_init_device(struct zram *zram) } zram->init_done = 1; + mutex_unlock(&zram->init_lock); pr_debug("Initialization done!\n"); return 0; fail: + mutex_unlock(&zram->init_lock); zram_reset_device(zram); pr_err("Initialization failed: err=%d\n", ret); @@ -572,6 +582,7 @@ static int create_device(struct zram *zram, int device_id) int ret = 0; mutex_init(&zram->lock); + mutex_init(&zram->init_lock); spin_lock_init(&zram->stat64_lock); zram->queue = blk_alloc_queue(GFP_KERNEL); diff --git a/drivers/staging/zram/zram_drv.h b/drivers/staging/zram/zram_drv.h index 2ef93cc..a481551 100644 --- a/drivers/staging/zram/zram_drv.h +++ b/drivers/staging/zram/zram_drv.h @@ -108,6 +108,8 @@ struct zram { struct request_queue *queue; struct gendisk *disk; int init_done; + /* Prevent concurrent execution of device init and reset */ + struct mutex init_lock; /* * This is the limit on amount of *uncompressed* worth of data * we can store in a disk. diff --git a/drivers/staging/zram/zram_sysfs.c b/drivers/staging/zram/zram_sysfs.c index b8dbaee..6c574a9 100644 --- a/drivers/staging/zram/zram_sysfs.c +++ b/drivers/staging/zram/zram_sysfs.c @@ -58,8 +58,10 @@ static ssize_t disksize_store(struct device *dev, int ret; struct zram *zram = dev_to_zram(dev); - if (zram->init_done) + if (zram->init_done) { + pr_info("Cannot change disksize for initialized device\n"); return -EBUSY; + } ret = strict_strtoull(buf, 10, &zram->disksize); if (ret) @@ -79,25 +81,6 @@ static ssize_t initstate_show(struct device *dev, return sprintf(buf, "%u\n", zram->init_done); } -static ssize_t initstate_store(struct device *dev, - struct device_attribute *attr, const char *buf, size_t len) -{ - int ret; - unsigned long do_init; - struct zram *zram = dev_to_zram(dev); - - ret = strict_strtoul(buf, 10, &do_init); - if (ret) - return ret; - - if (!do_init) - return -EINVAL; - - zram_init_device(zram); - - return len; -} - static ssize_t reset_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t len) { @@ -208,8 +191,7 @@ static ssize_t mem_used_total_show(struct device *dev, static DEVICE_ATTR(disksize, S_IRUGO | S_IWUGO, disksize_show, disksize_store); -static DEVICE_ATTR(initstate, S_IRUGO | S_IWUGO, - initstate_show, initstate_store); +static DEVICE_ATTR(initstate, S_IRUGO, initstate_show, NULL); static DEVICE_ATTR(reset, S_IWUGO, NULL, reset_store); static DEVICE_ATTR(num_reads, S_IRUGO, num_reads_show, NULL); static DEVICE_ATTR(num_writes, S_IRUGO, num_writes_show, NULL); -- 1.7.2.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/