Add a parameter "start_sector". It is offset in the unit of 512-byte
sectors from the start of the cache device. The sectors below the offset
are unused and they may be used for userspace metadata.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
---
Documentation/device-mapper/writecache.txt | 2 +
drivers/md/dm-writecache.c | 43 +++++++++++++++++++----------
2 files changed, 31 insertions(+), 14 deletions(-)
Index: linux-2.6/drivers/md/dm-writecache.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-writecache.c 2018-06-27 20:54:00.000000000 +0200
+++ linux-2.6/drivers/md/dm-writecache.c 2018-06-29 02:57:46.260000000 +0200
@@ -136,6 +136,7 @@ struct dm_writecache {
struct dm_target *ti;
struct dm_dev *dev;
struct dm_dev *ssd_dev;
+ sector_t start_sector;
void *memory_map;
uint64_t memory_map_size;
size_t metadata_sectors;
@@ -293,6 +294,10 @@ static int persistent_memory_claim(struc
}
dax_read_unlock(id);
+
+ wc->memory_map += (size_t)wc->start_sector << SECTOR_SHIFT;
+ wc->memory_map_size -= (size_t)wc->start_sector << SECTOR_SHIFT;
+
return 0;
err3:
kvfree(pages);
@@ -311,7 +316,7 @@ static int persistent_memory_claim(struc
static void persistent_memory_release(struct dm_writecache *wc)
{
if (wc->memory_vmapped)
- vunmap(wc->memory_map);
+ vunmap(wc->memory_map - ((size_t)wc->start_sector << SECTOR_SHIFT));
}
static struct page *persistent_memory_page(void *addr)
@@ -359,7 +364,7 @@ static void *memory_data(struct dm_write
static sector_t cache_sector(struct dm_writecache *wc, struct wc_entry *e)
{
- return wc->metadata_sectors +
+ return wc->start_sector + wc->metadata_sectors +
((sector_t)e->index << (wc->block_size_bits - SECTOR_SHIFT));
}
@@ -471,6 +476,7 @@ static void ssd_commit_flushed(struct dm
if (unlikely(region.sector + region.count > wc->metadata_sectors))
region.count = wc->metadata_sectors - region.sector;
+ region.sector += wc->start_sector;
atomic_inc(&endio.count);
req.bi_op = REQ_OP_WRITE;
req.bi_op_flags = REQ_SYNC;
@@ -1946,14 +1952,6 @@ static int writecache_ctr(struct dm_targ
}
wc->memory_map_size = i_size_read(wc->ssd_dev->bdev->bd_inode);
- if (WC_MODE_PMEM(wc)) {
- r = persistent_memory_claim(wc);
- if (r) {
- ti->error = "Unable to map persistent memory for cache";
- goto bad;
- }
- }
-
/*
* Parse the cache block size
*/
@@ -1982,7 +1980,16 @@ static int writecache_ctr(struct dm_targ
while (opt_params) {
string = dm_shift_arg(&as), opt_params--;
- if (!strcasecmp(string, "high_watermark") && opt_params >= 1) {
+ if (!strcasecmp(string, "start_sector") && opt_params >= 1) {
+ unsigned long long start_sector;
+ string = dm_shift_arg(&as), opt_params--;
+ if (sscanf(string, "%llu%c", &start_sector, &dummy) != 1)
+ goto invalid_optional;
+ wc->start_sector = start_sector;
+ if (wc->start_sector != start_sector ||
+ wc->start_sector >= wc->memory_map_size >> SECTOR_SHIFT)
+ goto invalid_optional;
+ } else if (!strcasecmp(string, "high_watermark") && opt_params >= 1) {
string = dm_shift_arg(&as), opt_params--;
if (sscanf(string, "%d%c", &high_wm_percent, &dummy) != 1)
goto invalid_optional;
@@ -2039,12 +2046,20 @@ invalid_optional:
goto bad;
}
- if (!WC_MODE_PMEM(wc)) {
+ if (WC_MODE_PMEM(wc)) {
+ r = persistent_memory_claim(wc);
+ if (r) {
+ ti->error = "Unable to map persistent memory for cache";
+ goto bad;
+ }
+ } else {
struct dm_io_region region;
struct dm_io_request req;
size_t n_blocks, n_metadata_blocks;
uint64_t n_bitmap_bits;
+ wc->memory_map_size -= (uint64_t)wc->start_sector << SECTOR_SHIFT;
+
bio_list_init(&wc->flush_list);
wc->flush_thread = kthread_create(writecache_flush_thread, wc, "dm_writecache_flush");
if (IS_ERR(wc->flush_thread)) {
@@ -2097,7 +2112,7 @@ invalid_optional:
}
region.bdev = wc->ssd_dev->bdev;
- region.sector = 0;
+ region.sector = wc->start_sector;
region.count = wc->metadata_sectors;
req.bi_op = REQ_OP_READ;
req.bi_op_flags = REQ_SYNC;
@@ -2265,7 +2280,7 @@ static void writecache_status(struct dm_
static struct target_type writecache_target = {
.name = "writecache",
- .version = {1, 0, 0},
+ .version = {1, 1, 0},
.module = THIS_MODULE,
.ctr = writecache_ctr,
.dtr = writecache_dtr,
Index: linux-2.6/Documentation/device-mapper/writecache.txt
===================================================================
--- linux-2.6.orig/Documentation/device-mapper/writecache.txt 2018-06-18 01:11:41.400000000 +0200
+++ linux-2.6/Documentation/device-mapper/writecache.txt 2018-06-29 02:57:04.360000000 +0200
@@ -15,6 +15,8 @@ Constructor parameters:
size)
5. the number of optional parameters (the parameters with an argument
count as two)
+ start_sector n (default: 0)
+ offset from the start of cache device in 512-byte sectors
high_watermark n (default: 50)
start writeback when the number of used blocks reach this
watermark
--
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