Implement module parameter 'rd_mem_size' to restrict the overall
allocated memory size and 'rd_lowat_thresh' to add a low water mark
signalling.
Signed-off-by: Hannes Reinecke <h...@suse.com>
---
drivers/block/brd.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index cb27190..a8848c3 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -30,6 +30,13 @@
#define PAGE_SECTORS (1 << PAGE_SECTORS_SHIFT)
/*
+ * Thin provisioning support
+ */
+static unsigned int rd_total_pages;
+static int rd_mem_size = CONFIG_BLK_DEV_RAM_SIZE * CONFIG_BLK_DEV_RAM_COUNT;
+static int rd_lowat_thresh = CONFIG_BLK_DEV_RAM_SIZE *
CONFIG_BLK_DEV_RAM_COUNT;
+
+/*
* Each block ramdisk device has a radix_tree brd_pages of pages that stores
* the pages containing the block device's contents. A brd page's ->index is
* its offset in PAGE_SIZE units. This is similar to, but in no way connected
@@ -44,6 +51,12 @@ struct brd_device {
struct list_head brd_list;
/*
+ * Thin provisioning support
+ */
+ unsigned int disk_events;
+ unsigned int pending_events;
+
+ /*
* Backing store of pages and lock to protect it. This is the contents
* of the block device.
*/
@@ -91,11 +104,23 @@ static struct page *brd_insert_page(struct brd_device
*brd, sector_t sector)
pgoff_t idx;
struct page *page;
gfp_t gfp_flags;
+ unsigned int rd_max_pages = rd_mem_size >> (PAGE_CACHE_SHIFT - 10);
+ unsigned int rd_lowat_pages = rd_lowat_thresh >> (PAGE_CACHE_SHIFT -
10);
page = brd_lookup_page(brd, sector);
if (page)
return page;
+ if (rd_total_pages >= rd_max_pages)
+ return NULL;
+
+ if (rd_total_pages >= rd_lowat_pages &&
+ !(brd->disk_events & DISK_EVENT_LOWAT)) {
+ brd->pending_events |= DISK_EVENT_LOWAT;
+ brd->disk_events |= DISK_EVENT_LOWAT;
+ disk_clear_events(brd->brd_disk, DISK_EVENT_LOWAT);
+ }
+
/*
* Must use NOIO because we don't want to recurse back into the
* block or filesystem layers from page reclaim.
@@ -127,6 +152,7 @@ static struct page *brd_insert_page(struct brd_device *brd,
sector_t sector)
BUG_ON(!page);
BUG_ON(page->index != idx);
}
+ rd_total_pages++;
spin_unlock(&brd->brd_lock);
radix_tree_preload_end();
@@ -138,10 +164,16 @@ static void brd_free_page(struct brd_device *brd,
sector_t sector)
{
struct page *page;
pgoff_t idx;
+ unsigned int rd_lowat_pages = rd_lowat_thresh >> (PAGE_CACHE_SHIFT -
10);
spin_lock(&brd->brd_lock);
idx = sector >> PAGE_SECTORS_SHIFT;
page = radix_tree_delete(&brd->brd_pages, idx);
+ rd_total_pages--;
+ if (rd_total_pages < rd_lowat_pages) {
+ brd->disk_events &= ~DISK_EVENT_LOWAT;
+ brd->pending_events &= ~DISK_EVENT_LOWAT;
+ }
spin_unlock(&brd->brd_lock);
if (page)
__free_page(page);
@@ -434,11 +466,22 @@ static int brd_ioctl(struct block_device *bdev, fmode_t
mode,
return error;
}
+static unsigned int brd_check_events(struct gendisk *disk, unsigned int mask)
+{
+ struct brd_device *brd = disk->private_data;
+ unsigned int pending_events = brd->pending_events & mask;
+
+ brd->pending_events &= ~mask;
+
+ return pending_events;
+}
+
static const struct block_device_operations brd_fops = {
.owner = THIS_MODULE,
.rw_page = brd_rw_page,
.ioctl = brd_ioctl,
.direct_access = brd_direct_access,
+ .check_events = brd_check_events,
};
/*
@@ -456,6 +499,12 @@ static int max_part = 1;
module_param(max_part, int, S_IRUGO);
MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices");
+module_param(rd_mem_size, int, S_IRUGO);
+MODULE_PARM_DESC(rd_mem_size, "Maximal memory size in kbytes to allocate");
+
+module_param(rd_lowat_thresh, int, S_IRUGO);
+MODULE_PARM_DESC(rd_lowat_thresh, "Low water mark in kbytes for memory
allocation");
+
MODULE_LICENSE("GPL");
MODULE_ALIAS_BLOCKDEV_MAJOR(RAMDISK_MAJOR);
MODULE_ALIAS("rd");
@@ -519,6 +568,8 @@ static struct brd_device *brd_alloc(int i)
disk->private_data = brd;
disk->queue = brd->brd_queue;
disk->flags = GENHD_FL_EXT_DEVT;
+ disk->events = DISK_EVENT_LOWAT;
+ disk->async_events = DISK_EVENT_LOWAT;
sprintf(disk->disk_name, "ram%d", i);
set_capacity(disk, rd_size * 2);
@@ -607,6 +658,8 @@ static int __init brd_init(void)
if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
return -EIO;
+ rd_total_pages = 0;
+
if (unlikely(!max_part))
max_part = 1;
--
1.8.5.6
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