[PATCH 04/29] dax: simplify the dax_device <-> gendisk association

Christoph Hellwig
2021-11-09T08:33:32Z

Replace the dax_host_hash with an xarray indexed by the pointer value
of the gendisk, and require explicitly calls from the block drivers that
want to associate their gendisk with a dax_device.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/dax/bus.c | 6 +-
drivers/dax/super.c | 106 +++++++++--------------------------
drivers/md/dm.c | 6 +-
drivers/nvdimm/pmem.c | 8 ++-
drivers/s390/block/dcssblk.c | 11 +++-
fs/fuse/virtio_fs.c | 2 +-
include/linux/dax.h | 19 +++++--
7 files changed, 62 insertions(+), 96 deletions(-)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 6cc4da4c713d9..bd7af2f7c5b0a 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -1323,10 +1323,10 @@ struct dev_dax *devm_create_dev_dax(struct dev_dax_data *data)
}

/*
- * No 'host' or dax_operations since there is no access to this
- * device outside of mmap of the resulting character device.
+ * No 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, DAXDEV_F_SYNC);
+ dax_dev = alloc_dax(dev_dax, NULL, DAXDEV_F_SYNC);
if (IS_ERR(dax_dev)) {
rc = PTR_ERR(dax_dev);
goto err_alloc_dax;
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index e20d0cef10a18..9383c11b21853 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -7,10 +7,8 @@
#include <linux/mount.h>
#include <linux/pseudo_fs.h>
#include <linux/magic.h>
-#include <linux/genhd.h>
#include <linux/pfn_t.h>
#include <linux/cdev.h>
-#include <linux/hash.h>
#include <linux/slab.h>
#include <linux/uio.h>
#include <linux/dax.h>
@@ -26,10 +24,8 @@
* @flags: state and boolean properties
*/
struct dax_device {
- struct hlist_node list;
struct inode inode;
struct cdev cdev;
- const char *host;
void *private;
unsigned long flags;
const struct dax_operations *ops;
@@ -42,10 +38,6 @@ static DEFINE_IDA(dax_minor_ida);
static struct kmem_cache *dax_cache __read_mostly;
static struct super_block *dax_superblock __read_mostly;

-#define DAX_HASH_SIZE (PAGE_SIZE / sizeof(struct hlist_head))
-static struct hlist_head dax_host_list[DAX_HASH_SIZE];
-static DEFINE_SPINLOCK(dax_host_lock);
-
int dax_read_lock(void)
{
return srcu_read_lock(&dax_srcu);
@@ -58,13 +50,22 @@ void dax_read_unlock(int id)
}
EXPORT_SYMBOL_GPL(dax_read_unlock);

-static int dax_host_hash(const char *host)
+#if defined(CONFIG_BLOCK) && defined(CONFIG_FS_DAX)
+#include <linux/blkdev.h>
+
+static DEFINE_XARRAY(dax_hosts);
+
+int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk)
{
- return hashlen_hash(hashlen_string("DAX", host)) % DAX_HASH_SIZE;
+ return xa_insert(&dax_hosts, (unsigned long)disk, dax_dev, GFP_KERNEL);
}
+EXPORT_SYMBOL_GPL(dax_add_host);

-#if defined(CONFIG_BLOCK) && defined(CONFIG_FS_DAX)
-#include <linux/blkdev.h>
+void dax_remove_host(struct gendisk *disk)
+{
+ xa_erase(&dax_hosts, (unsigned long)disk);
+}
+EXPORT_SYMBOL_GPL(dax_remove_host);

int bdev_dax_pgoff(struct block_device *bdev, sector_t sector, size_t size,
pgoff_t *pgoff)
@@ -82,40 +83,23 @@ EXPORT_SYMBOL(bdev_dax_pgoff);

/**
* dax_get_by_host() - temporary lookup mechanism for filesystem-dax
- * @host: alternate name for the device registered by a dax driver
+ * @bdev: block device to find a dax_device for
*/
-static struct dax_device *dax_get_by_host(const char *host)
+struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev)
{
- struct dax_device *dax_dev, *found = NULL;
- int hash, id;
+ struct dax_device *dax_dev;
+ int id;

- if (!host)
+ if (!blk_queue_dax(bdev->bd_disk->queue))
return NULL;

- hash = dax_host_hash(host);
-
id = dax_read_lock();
- spin_lock(&dax_host_lock);
- hlist_for_each_entry(dax_dev, &dax_host_list[hash], list) {
- if (!dax_alive(dax_dev)
- || strcmp(host, dax_dev->host) != 0)
- continue;
-
- if (igrab(&dax_dev->inode))
- found = dax_dev;
- break;
- }
- spin_unlock(&dax_host_lock);
+ dax_dev = xa_load(&dax_hosts, (unsigned long)bdev->bd_disk);
+ if (!dax_dev || !dax_alive(dax_dev) || !igrab(&dax_dev->inode))
+ dax_dev = NULL;
dax_read_unlock(id);

- return found;
-}
-
-struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev)
-{
- if (!blk_queue_dax(bdev->bd_disk->queue))
- return NULL;
- return dax_get_by_host(bdev->bd_disk->disk_name);
+ return dax_dev;
}
EXPORT_SYMBOL_GPL(fs_dax_get_by_bdev);

@@ -361,12 +345,7 @@ void kill_dax(struct dax_device *dax_dev)
return;

clear_bit(DAXDEV_ALIVE, &dax_dev->flags);
-
synchronize_srcu(&dax_srcu);
-
- spin_lock(&dax_host_lock);
- hlist_del_init(&dax_dev->list);
- spin_unlock(&dax_host_lock);
}
EXPORT_SYMBOL_GPL(kill_dax);

@@ -398,8 +377,6 @@ static struct dax_device *to_dax_dev(struct inode *inode)
static void dax_free_inode(struct inode *inode)
{
struct dax_device *dax_dev = to_dax_dev(inode);
- kfree(dax_dev->host);
- dax_dev->host = NULL;
if (inode->i_rdev)
ida_simple_remove(&dax_minor_ida, iminor(inode));
kmem_cache_free(dax_cache, dax_dev);
@@ -474,54 +451,25 @@ static struct dax_device *dax_dev_get(dev_t devt)
return dax_dev;
}

-static void dax_add_host(struct dax_device *dax_dev, const char *host)
-{
- int hash;
-
- /*
- * Unconditionally init dax_dev since it's coming from a
- * non-zeroed slab cache
- */
- INIT_HLIST_NODE(&dax_dev->list);
- dax_dev->host = host;
- if (!host)
- return;
-
- hash = dax_host_hash(host);
- spin_lock(&dax_host_lock);
- hlist_add_head(&dax_dev->list, &dax_host_list[hash]);
- spin_unlock(&dax_host_lock);
-}
-
-struct dax_device *alloc_dax(void *private, const char *__host,
- const struct dax_operations *ops, unsigned long flags)
+struct dax_device *alloc_dax(void *private, const struct dax_operations *ops,
+ unsigned long flags)
{
struct dax_device *dax_dev;
- const char *host;
dev_t devt;
int minor;

- if (ops && !ops->zero_page_range) {
- pr_debug("%s: error: device does not provide dax"
- " operation zero_page_range()\n",
- __host ? __host : "Unknown");
+ if (WARN_ON_ONCE(ops && !ops->zero_page_range))
return ERR_PTR(-EINVAL);
- }
-
- host = kstrdup(__host, GFP_KERNEL);
- if (__host && !host)
- return ERR_PTR(-ENOMEM);

minor = ida_simple_get(&dax_minor_ida, 0, MINORMASK+1, GFP_KERNEL);
if (minor < 0)
- goto err_minor;
+ return ERR_PTR(-ENOMEM);

devt = MKDEV(MAJOR(dax_devt), minor);
dax_dev = dax_dev_get(devt);
if (!dax_dev)
goto err_dev;

- dax_add_host(dax_dev, host);
dax_dev->ops = ops;
dax_dev->private = private;
if (flags & DAXDEV_F_SYNC)
@@ -531,8 +479,6 @@ struct dax_device *alloc_dax(void *private, const char *__host,

err_dev:
ida_simple_remove(&dax_minor_ida, minor);
- err_minor:
- kfree(host);
return ERR_PTR(-ENOMEM);
}
EXPORT_SYMBOL_GPL(alloc_dax);
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 893fca738a3d8..782a076f61f81 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1683,6 +1683,7 @@ static void cleanup_mapped_device(struct mapped_device *md)
bioset_exit(&md->io_bs);

if (md->dax_dev) {
+ dax_remove_host(md->disk);
kill_dax(md->dax_dev);
put_dax(md->dax_dev);
md->dax_dev = NULL;
@@ -1784,10 +1785,11 @@ static struct mapped_device *alloc_dev(int minor)
sprintf(md->disk->disk_name, "dm-%d", minor);

if (IS_ENABLED(CONFIG_FS_DAX)) {
- md->dax_dev = alloc_dax(md, md->disk->disk_name,
- &dm_dax_ops, 0);
+ md->dax_dev = alloc_dax(md, &dm_dax_ops, 0);
if (IS_ERR(md->dax_dev))
goto bad;
+ if (dax_add_host(md->dax_dev, md->disk))
+ goto bad;
}

format_dev_t(md->name, MKDEV(_major, minor));
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 9cc0d0ebfad16..8783ad7370856 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -379,6 +379,7 @@ static void pmem_release_disk(void *__pmem)
{
struct pmem_device *pmem = __pmem;

+ dax_remove_host(pmem->disk);
kill_dax(pmem->dax_dev);
put_dax(pmem->dax_dev);
del_gendisk(pmem->disk);
@@ -495,10 +496,11 @@ static int pmem_attach_disk(struct device *dev,

if (is_nvdimm_sync(nd_region))
flags = DAXDEV_F_SYNC;
- dax_dev = alloc_dax(pmem, disk->disk_name, &pmem_dax_ops, flags);
- if (IS_ERR(dax_dev)) {
+ dax_dev = alloc_dax(pmem, &pmem_dax_ops, flags);
+ if (IS_ERR(dax_dev))
return PTR_ERR(dax_dev);
- }
+ if (dax_add_host(dax_dev, disk))
+ return -ENOMEM;
dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
pmem->dax_dev = dax_dev;

diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index 27ab888b44d0a..657e492f2bc26 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -687,18 +687,21 @@ dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char
if (rc)
goto put_dev;

- dev_info->dax_dev = alloc_dax(dev_info, dev_info->gd->disk_name,
- &dcssblk_dax_ops, DAXDEV_F_SYNC);
+ dev_info->dax_dev = alloc_dax(dev_info, &dcssblk_dax_ops,
+ DAXDEV_F_SYNC);
if (IS_ERR(dev_info->dax_dev)) {
rc = PTR_ERR(dev_info->dax_dev);
dev_info->dax_dev = NULL;
goto put_dev;
}
+ rc = dax_add_host(dev_info->dax_dev, dev_info->gd);
+ if (rc)
+ goto out_dax;

get_device(&dev_info->dev);
rc = device_add_disk(&dev_info->dev, dev_info->gd, NULL);
if (rc)
- goto out_dax;
+ goto out_dax_host;

switch (dev_info->segment_type) {
case SEG_TYPE_SR:
@@ -714,6 +717,8 @@ dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char
rc = count;
goto out;

+out_dax_host:
+ dax_remove_host(dev_info->gd);
out_dax:
put_device(&dev_info->dev);
kill_dax(dev_info->dax_dev);
diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 94fc874f5de7f..b4c7c7fa987f8 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -850,7 +850,7 @@ static int virtio_fs_setup_dax(struct virtio_device *vdev, struct virtio_fs *fs)
dev_dbg(&vdev->dev, "%s: window kaddr 0x%px phys_addr 0x%llx len 0x%llx\n",
__func__, fs->window_kaddr, cache_reg.addr, cache_reg.len);

- fs->dax_dev = alloc_dax(fs, NULL, &virtio_fs_dax_ops, 0);
+ fs->dax_dev = alloc_dax(fs, &virtio_fs_dax_ops, 0);
if (IS_ERR(fs->dax_dev))
return PTR_ERR(fs->dax_dev);

diff --git a/include/linux/dax.h b/include/linux/dax.h
index 8623caa673889..e2e9a67004cbd 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -11,9 +11,11 @@

typedef unsigned long dax_entry_t;

+struct dax_device;
+struct gendisk;
struct iomap_ops;
struct iomap;
-struct dax_device;
+
struct dax_operations {
/*
* direct_access: translate a device-relative
@@ -39,8 +41,8 @@ struct dax_operations {
};

#if IS_ENABLED(CONFIG_DAX)
-struct dax_device *alloc_dax(void *private, const char *host,
- const struct dax_operations *ops, unsigned long flags);
+struct dax_device *alloc_dax(void *private, 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);
@@ -68,7 +70,7 @@ static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
return dax_synchronous(dax_dev);
}
#else
-static inline struct dax_device *alloc_dax(void *private, const char *host,
+static inline struct dax_device *alloc_dax(void *private,
const struct dax_operations *ops, unsigned long flags)
{
/*
@@ -107,6 +109,8 @@ static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
struct writeback_control;
int bdev_dax_pgoff(struct block_device *, sector_t, size_t, pgoff_t *pgoff);
#if IS_ENABLED(CONFIG_FS_DAX)
+int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk);
+void dax_remove_host(struct gendisk *disk);
bool generic_fsdax_supported(struct dax_device *dax_dev,
struct block_device *bdev, int blocksize, sector_t start,
sector_t sectors);
@@ -128,6 +132,13 @@ struct page *dax_layout_busy_page_range(struct address_space *mapping, loff_t st
dax_entry_t dax_lock_page(struct page *page);
void dax_unlock_page(struct page *page, dax_entry_t cookie);
#else
+static inline int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk)
+{
+ return 0;
+}
+static inline void dax_remove_host(struct gendisk *disk)
+{
+}
#define generic_fsdax_supported NULL

static inline bool dax_supported(struct dax_device *dax_dev,
--
2.30.2