[Qemu-devel] [PATCH v9 3/7] libnvdimm: add dax_dev sync flag

[Pankaj Gupta]

This patch adds 'DAXDEV_SYNC' flag which is set
for nd_region doing synchronous flush. This later
is used to disable MAP_SYNC functionality for
ext4 & xfs filesystem for devices don't support
synchronous flush.

Signed-off-by: Pankaj Gupta <address@hidden>
---
 drivers/dax/bus.c            |  2 +-
 drivers/dax/super.c          | 19 ++++++++++++++++++-
 drivers/md/dm.c              |  3 ++-
 drivers/nvdimm/pmem.c        |  5 ++++-
 drivers/nvdimm/region_devs.c |  7 +++++++
 include/linux/dax.h          |  9 +++++++--
 include/linux/libnvdimm.h    |  1 +
 7 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 2109cfe80219..5f184e751c82 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -388,7 +388,7 @@ struct dev_dax *__devm_create_dev_dax(struct dax_region 
*dax_region, int id,
         * No 'host' or dax_operations since there is no access to this
         * device outside of mmap of the resulting character device.
         */
-       dax_dev = alloc_dax(dev_dax, NULL, NULL);
+       dax_dev = alloc_dax(dev_dax, NULL, NULL, DAXDEV_F_SYNC);
        if (!dax_dev)
                goto err;
 
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index bbd57ca0634a..93b3718b5cfa 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -186,6 +186,8 @@ enum dax_device_flags {
        DAXDEV_ALIVE,
        /* gate whether dax_flush() calls the low level flush routine */
        DAXDEV_WRITE_CACHE,
+       /* flag to check if device supports synchronous flush */
+       DAXDEV_SYNC,
 };
 
 /**
@@ -354,6 +356,18 @@ bool dax_write_cache_enabled(struct dax_device *dax_dev)
 }
 EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
 
+bool dax_synchronous(struct dax_device *dax_dev)
+{
+       return test_bit(DAXDEV_SYNC, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(dax_synchronous);
+
+void set_dax_synchronous(struct dax_device *dax_dev)
+{
+       set_bit(DAXDEV_SYNC, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(set_dax_synchronous);
+
 bool dax_alive(struct dax_device *dax_dev)
 {
        lockdep_assert_held(&dax_srcu);
@@ -508,7 +522,7 @@ static void dax_add_host(struct dax_device *dax_dev, const 
char *host)
 }
 
 struct dax_device *alloc_dax(void *private, const char *__host,
-               const struct dax_operations *ops)
+               const struct dax_operations *ops, unsigned long flags)
 {
        struct dax_device *dax_dev;
        const char *host;
@@ -531,6 +545,9 @@ struct dax_device *alloc_dax(void *private, const char 
*__host,
        dax_add_host(dax_dev, host);
        dax_dev->ops = ops;
        dax_dev->private = private;
+       if (flags & DAXDEV_F_SYNC)
+               set_dax_synchronous(dax_dev);
+
        return dax_dev;
 
  err_dev:
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 043f0761e4a0..ee007b75d9fd 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1969,7 +1969,8 @@ static struct mapped_device *alloc_dev(int minor)
        sprintf(md->disk->disk_name, "dm-%d", minor);
 
        if (IS_ENABLED(CONFIG_DAX_DRIVER)) {
-               dax_dev = alloc_dax(md, md->disk->disk_name, &dm_dax_ops);
+               dax_dev = alloc_dax(md, md->disk->disk_name, &dm_dax_ops,
+                                                        DAXDEV_F_SYNC);
                if (!dax_dev)
                        goto bad;
        }
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 0279eb1da3ef..bdbd2b414d3d 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -365,6 +365,7 @@ static int pmem_attach_disk(struct device *dev,
        struct gendisk *disk;
        void *addr;
        int rc;
+       unsigned long flags = 0UL;
 
        pmem = devm_kzalloc(dev, sizeof(*pmem), GFP_KERNEL);
        if (!pmem)
@@ -462,7 +463,9 @@ static int pmem_attach_disk(struct device *dev,
        nvdimm_badblocks_populate(nd_region, &pmem->bb, &bb_res);
        disk->bb = &pmem->bb;
 
-       dax_dev = alloc_dax(pmem, disk->disk_name, &pmem_dax_ops);
+       if (is_nvdimm_sync(nd_region))
+               flags = DAXDEV_F_SYNC;
+       dax_dev = alloc_dax(pmem, disk->disk_name, &pmem_dax_ops, flags);
        if (!dax_dev) {
                put_disk(disk);
                return -ENOMEM;
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index b4ef7d9ff22e..f3ea5369d20a 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1197,6 +1197,13 @@ int nvdimm_has_cache(struct nd_region *nd_region)
 }
 EXPORT_SYMBOL_GPL(nvdimm_has_cache);
 
+bool is_nvdimm_sync(struct nd_region *nd_region)
+{
+       return is_nd_pmem(&nd_region->dev) &&
+               !test_bit(ND_REGION_ASYNC, &nd_region->flags);
+}
+EXPORT_SYMBOL_GPL(is_nvdimm_sync);
+
 struct conflict_context {
        struct nd_region *nd_region;
        resource_size_t start, size;
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 0dd316a74a29..2b106752b1b8 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -7,6 +7,9 @@
 #include <linux/radix-tree.h>
 #include <asm/pgtable.h>
 
+/* Flag for synchronous flush */
+#define DAXDEV_F_SYNC (1UL << 0)
+
 typedef unsigned long dax_entry_t;
 
 struct iomap_ops;
@@ -32,18 +35,20 @@ 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);
+               const struct dax_operations *ops, unsigned long flags);
 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);
+bool dax_synchronous(struct dax_device *dax_dev);
+void set_dax_synchronous(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)
+               const struct dax_operations *ops, unsigned long flags)
 {
        /*
         * Callers should check IS_ENABLED(CONFIG_DAX) to know if this
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index feb342d026f2..3238a206e563 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -264,6 +264,7 @@ void nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 int nvdimm_in_overwrite(struct nvdimm *nvdimm);
+bool is_nvdimm_sync(struct nd_region *nd_region);
 
 static inline int nvdimm_ctl(struct nvdimm *nvdimm, unsigned int cmd, void 
*buf,
                unsigned int buf_len, int *cmd_rc)
-- 
2.20.1