dax: remove the copy_from_iter and copy_to_iter methods

These methods indirect the actual DAX read/write path.  In the end pmem
uses magic flush and mc safe variants and fuse and dcssblk use plain ones
while device mapper picks redirects to the underlying device.

Add set_dax_nocache() and set_dax_nomc() APIs to control which copy
routines are used to remove indirect call from the read/write fast path
as well as a lot of boilerplate code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com> [virtiofs]
Link: https://lore.kernel.org/r/20211215084508.435401-5-hch@lst.de
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 0 insertions, 80 deletions

diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
index cdb22e7a1d0d..139b09b06eda 100644
--- a/drivers/md/dm-log-writes.c
+++ b/drivers/md/dm-log-writes.c
@@ -902,51 +902,6 @@ static void log_writes_io_hints(struct dm_target *ti, struct queue_limits *limit
 }
 
 #if IS_ENABLED(CONFIG_FS_DAX)
-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 struct dax_device *log_writes_dax_pgoff(struct dm_target *ti,
 		pgoff_t *pgoff)
 {
@@ -964,37 +919,6 @@ static long log_writes_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
 	return dax_direct_access(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;
-	struct dax_device *dax_dev = log_writes_dax_pgoff(ti, &pgoff);
-	int err;
-
-	/* 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(dax_dev, pgoff, addr, bytes, i);
-}
-
-static size_t log_writes_dax_copy_to_iter(struct dm_target *ti,
-					  pgoff_t pgoff, void *addr, size_t bytes,
-					  struct iov_iter *i)
-{
-	struct dax_device *dax_dev = log_writes_dax_pgoff(ti, &pgoff);
-
-	return dax_copy_to_iter(dax_dev, pgoff, addr, bytes, i);
-}
-
 static int log_writes_dax_zero_page_range(struct dm_target *ti, pgoff_t pgoff,
 					  size_t nr_pages)
 {
@@ -1005,8 +929,6 @@ static int log_writes_dax_zero_page_range(struct dm_target *ti, pgoff_t pgoff,
 
 #else
 #define log_writes_dax_direct_access NULL
-#define log_writes_dax_copy_from_iter NULL
-#define log_writes_dax_copy_to_iter NULL
 #define log_writes_dax_zero_page_range NULL
 #endif
 
@@ -1024,8 +946,6 @@ static struct target_type log_writes_target = {
 	.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,
-	.dax_copy_to_iter = log_writes_dax_copy_to_iter,
 	.dax_zero_page_range = log_writes_dax_zero_page_range,
 };