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dm writecache: support optional offset for start of device

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Add an optional parameter "start_sector" to allow the start of the
device to be offset by the specified number of 512-byte sectors.  The
sectors below this offset are not used by the writecache device and are
left to be used for disk labels and/or userspace metadata (e.g. lvm).

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mikulas Patocka 2018-06-28 21:00:14 -04:00 committed by Mike Snitzer
parent 021c91791a
commit d284f8248c
2 changed files with 31 additions and 14 deletions
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2
Documentation/device-mapper/writecache.txt
View File

@ -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

43
drivers/md/dm-writecache.c
View File

@ -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(struct dm_writecache *wc)
}
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(struct dm_writecache *wc)
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_writecache *wc, struct wc_entry *e)
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_writecache *wc)
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_target *ti, unsigned argc, char **argv)
}
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_target *ti, unsigned argc, char **argv)
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_target *ti, status_type_t type,
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,