[PATCH v8 09/18] dax, dm: allow device-mapper to operate without dax support

From: Dan Williams
Date: Sat Mar 31 2018 - 00:13:00 EST

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Change device-mapper's DAX dependency to require the presence of at
least one DAX_DRIVER. This allows device-mapper to be built without
bringing the DAX core along which is especially wasteful when there are
no DAX drivers, like BLK_DEV_PMEM, configured.

Cc: Alasdair Kergon <agk@xxxxxxxxxx>
Reported-by: Bart Van Assche <Bart.VanAssche@xxxxxxx>
Reported-by: kbuild test robot <lkp@xxxxxxxxx>
Reviewed-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
drivers/md/Kconfig | 1
drivers/md/dm-linear.c | 6 +++
drivers/md/dm-log-writes.c | 95 +++++++++++++++++++++++---------------------
drivers/md/dm-stripe.c | 6 +++
drivers/md/dm.c | 10 +++--
include/linux/dax.h | 30 +++++++++++---
6 files changed, 92 insertions(+), 56 deletions(-)

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 2c8ac3688815..6dfc328b8f99 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -201,7 +201,6 @@ config BLK_DEV_DM_BUILTIN
config BLK_DEV_DM
tristate "Device mapper support"
select BLK_DEV_DM_BUILTIN
- select DAX
---help---
Device-mapper is a low level volume manager. It works by allowing
people to specify mappings for ranges of logical sectors. Various
diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index d5f8eff7c11d..89443e0ededa 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -154,6 +154,7 @@ static int linear_iterate_devices(struct dm_target *ti,
return fn(ti, lc->dev, lc->start, ti->len, data);
}

+#if IS_ENABLED(CONFIG_DAX_DRIVER)
static long linear_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
long nr_pages, void **kaddr, pfn_t *pfn)
{
@@ -184,6 +185,11 @@ static size_t linear_dax_copy_from_iter(struct dm_target *ti, pgoff_t pgoff,
return dax_copy_from_iter(dax_dev, pgoff, addr, bytes, i);
}

+#else
+#define linear_dax_direct_access NULL
+#define linear_dax_copy_from_iter NULL
+#endif
+
static struct target_type linear_target = {
.name = "linear",
.version = {1, 4, 0},
diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
index 3362d866793b..7fcb4216973f 100644
--- a/drivers/md/dm-log-writes.c
+++ b/drivers/md/dm-log-writes.c
@@ -610,51 +610,6 @@ 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;
@@ -920,6 +875,52 @@ static void log_writes_io_hints(struct dm_target *ti, struct queue_limits *limit
limits->io_min = limits->physical_block_size;
}

+#if IS_ENABLED(CONFIG_DAX_DRIVER)
+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 long log_writes_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
long nr_pages, void **kaddr, pfn_t *pfn)
{
@@ -956,6 +957,10 @@ static size_t log_writes_dax_copy_from_iter(struct dm_target *ti,
dax_copy:
return dax_copy_from_iter(lc->dev->dax_dev, pgoff, addr, bytes, i);
}
+#else
+#define log_writes_dax_direct_access NULL
+#define log_writes_dax_copy_from_iter NULL
+#endif

static struct target_type log_writes_target = {
.name = "log-writes",
diff --git a/drivers/md/dm-stripe.c b/drivers/md/dm-stripe.c
index b5e892149c54..ac2e8ee9d586 100644
--- a/drivers/md/dm-stripe.c
+++ b/drivers/md/dm-stripe.c
@@ -311,6 +311,7 @@ static int stripe_map(struct dm_target *ti, struct bio *bio)
return DM_MAPIO_REMAPPED;
}

+#if IS_ENABLED(CONFIG_DAX_DRIVER)
static long stripe_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
long nr_pages, void **kaddr, pfn_t *pfn)
{
@@ -351,6 +352,11 @@ static size_t stripe_dax_copy_from_iter(struct dm_target *ti, pgoff_t pgoff,
return dax_copy_from_iter(dax_dev, pgoff, addr, bytes, i);
}

+#else
+#define stripe_dax_direct_access NULL
+#define stripe_dax_copy_from_iter NULL
+#endif
+
/*
* Stripe status:
*
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 68136806d365..ffc93aecc02a 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1800,7 +1800,7 @@ static void cleanup_mapped_device(struct mapped_device *md)
static struct mapped_device *alloc_dev(int minor)
{
int r, numa_node_id = dm_get_numa_node();
- struct dax_device *dax_dev;
+ struct dax_device *dax_dev = NULL;
struct mapped_device *md;
void *old_md;

@@ -1866,9 +1866,11 @@ static struct mapped_device *alloc_dev(int minor)
md->disk->private_data = md;
sprintf(md->disk->disk_name, "dm-%d", minor);

- dax_dev = alloc_dax(md, md->disk->disk_name, &dm_dax_ops);
- if (!dax_dev)
- goto bad;
+ if (IS_ENABLED(CONFIG_DAX_DRIVER)) {
+ dax_dev = alloc_dax(md, md->disk->disk_name, &dm_dax_ops);
+ if (!dax_dev)
+ goto bad;
+ }
md->dax_dev = dax_dev;

add_disk_no_queue_reg(md->disk);
diff --git a/include/linux/dax.h b/include/linux/dax.h
index ae27a7efe7ab..f9eb22ad341e 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -26,16 +26,39 @@ extern struct attribute_group dax_attribute_group;

#if IS_ENABLED(CONFIG_DAX)
struct dax_device *dax_get_by_host(const char *host);
+struct dax_device *alloc_dax(void *private, const char *host,
+ const struct dax_operations *ops);
void put_dax(struct dax_device *dax_dev);
+void kill_dax(struct dax_device *dax_dev);
+void dax_write_cache(struct dax_device *dax_dev, bool wc);
+bool dax_write_cache_enabled(struct dax_device *dax_dev);
#else
static inline struct dax_device *dax_get_by_host(const char *host)
{
return NULL;
}
-
+static inline struct dax_device *alloc_dax(void *private, const char *host,
+ const struct dax_operations *ops)
+{
+ /*
+ * Callers should check IS_ENABLED(CONFIG_DAX) to know if this
+ * NULL is an error or expected.
+ */
+ return NULL;
+}
static inline void put_dax(struct dax_device *dax_dev)
{
}
+static inline void kill_dax(struct dax_device *dax_dev)
+{
+}
+static inline void dax_write_cache(struct dax_device *dax_dev, bool wc)
+{
+}
+static inline bool dax_write_cache_enabled(struct dax_device *dax_dev)
+{
+ return false;
+}
#endif

struct writeback_control;
@@ -89,18 +112,13 @@ static inline int dax_writeback_mapping_range(struct address_space *mapping,

int dax_read_lock(void);
void dax_read_unlock(int id);
-struct dax_device *alloc_dax(void *private, const char *host,
- const struct dax_operations *ops);
bool dax_alive(struct dax_device *dax_dev);
-void kill_dax(struct dax_device *dax_dev);
void *dax_get_private(struct dax_device *dax_dev);
long dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff, long nr_pages,
void **kaddr, pfn_t *pfn);
size_t dax_copy_from_iter(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
size_t bytes, struct iov_iter *i);
void dax_flush(struct dax_device *dax_dev, void *addr, size_t size);
-void dax_write_cache(struct dax_device *dax_dev, bool wc);
-bool dax_write_cache_enabled(struct dax_device *dax_dev);

ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
const struct iomap_ops *ops);

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