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dm log writes: add support for DAX

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Now that we have the ability log filesystem writes using a flat buffer, add
support for DAX.

The motivation for this support is the need for an xfstest that can test
the new MAP_SYNC DAX flag.  By logging the filesystem activity with
dm-log-writes we can show that the MAP_SYNC page faults are writing out
their metadata as they happen, instead of requiring an explicit
msync/fsync.

Unfortunately we can't easily track data that has been written via
mmap() now that the dax_flush() abstraction was removed by commit
c3ca015fab ("dax: remove the pmem_dax_ops->flush abstraction").
Otherwise we could just treat each flush as a big write, and store the
data that is being synced to media.  It may be worthwhile to add the
dax_flush() entry point back, just as a notifier so we can do this
logging.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Ross Zwisler 2017-10-19 23:24:04 -06:00 committed by Mike Snitzer
parent e5a20660a1
commit 98d82f48f1
1 changed files with 87 additions and 1 deletions
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88
drivers/md/dm-log-writes.c
View File

@ -10,9 +10,11 @@
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/bio.h>
#include <linux/dax.h>
#include <linux/slab.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/uio.h>
#define DM_MSG_PREFIX "log-writes"
@ -608,6 +610,51 @@ static int log_mark(struct log_writes_c *lc, char *data)
return 0;
}
static int log_dax(struct log_writes_c *lc, sector_t sector, size_t bytes,
struct iov_iter *i)
{
struct pending_block *block;
if (!bytes)
return 0;
block = kzalloc(sizeof(struct pending_block), GFP_KERNEL);
if (!block) {
DMERR("Error allocating dax pending block");
return -ENOMEM;
}
block->data = kzalloc(bytes, GFP_KERNEL);
if (!block->data) {
DMERR("Error allocating dax data space");
kfree(block);
return -ENOMEM;
}
/* write data provided via the iterator */
if (!copy_from_iter(block->data, bytes, i)) {
DMERR("Error copying dax data");
kfree(block->data);
kfree(block);
return -EIO;
}
/* rewind the iterator so that the block driver can use it */
iov_iter_revert(i, bytes);
block->datalen = bytes;
block->sector = bio_to_dev_sectors(lc, sector);
block->nr_sectors = ALIGN(bytes, lc->sectorsize) >> lc->sectorshift;
atomic_inc(&lc->pending_blocks);
spin_lock_irq(&lc->blocks_lock);
list_add_tail(&block->list, &lc->unflushed_blocks);
spin_unlock_irq(&lc->blocks_lock);
wake_up_process(lc->log_kthread);
return 0;
}
static void log_writes_dtr(struct dm_target *ti)
{
struct log_writes_c *lc = ti->private;
@ -873,9 +920,46 @@ static void log_writes_io_hints(struct dm_target *ti, struct queue_limits *limit
limits->io_min = limits->physical_block_size;
}
static long log_writes_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
long nr_pages, void **kaddr, pfn_t *pfn)
{
struct log_writes_c *lc = ti->private;
sector_t sector = pgoff * PAGE_SECTORS;
int ret;
ret = bdev_dax_pgoff(lc->dev->bdev, sector, nr_pages * PAGE_SIZE, &pgoff);
if (ret)
return ret;
return dax_direct_access(lc->dev->dax_dev, pgoff, nr_pages, kaddr, pfn);
}
static size_t log_writes_dax_copy_from_iter(struct dm_target *ti,
pgoff_t pgoff, void *addr, size_t bytes,
struct iov_iter *i)
{
struct log_writes_c *lc = ti->private;
sector_t sector = pgoff * PAGE_SECTORS;
int err;
if (bdev_dax_pgoff(lc->dev->bdev, sector, ALIGN(bytes, PAGE_SIZE), &pgoff))
return 0;
/* Don't bother doing anything if logging has been disabled */
if (!lc->logging_enabled)
goto dax_copy;
err = log_dax(lc, sector, bytes, i);
if (err) {
DMWARN("Error %d logging DAX write", err);
return 0;
}
dax_copy:
return dax_copy_from_iter(lc->dev->dax_dev, pgoff, addr, bytes, i);
}
static struct target_type log_writes_target = {
.name = "log-writes",
.version = {1, 0, 0},
.version = {1, 1, 0},
.module = THIS_MODULE,
.ctr = log_writes_ctr,
.dtr = log_writes_dtr,
@ -886,6 +970,8 @@ static struct target_type log_writes_target = {
.message = log_writes_message,
.iterate_devices = log_writes_iterate_devices,
.io_hints = log_writes_io_hints,
.direct_access = log_writes_dax_direct_access,
.dax_copy_from_iter = log_writes_dax_copy_from_iter,
};
static int __init dm_log_writes_init(void)