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Message-ID: <149264098308.36586.14533308558533384197.stgit@dwillia2-desk3.amr.corp.intel.com>
Date: Wed, 19 Apr 2017 15:31:53 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: linux-nvdimm@...ts.01.org
Cc: linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
dm-devel@...hat.com, linux-kernel@...r.kernel.org, hch@....de
Subject: [PATCH v3] dax: add a facility to lookup a dax device by 'host'
device name
For the current block_device based filesystem-dax path, we need a way
for it to lookup the dax_device associated with a block_device. Add a
'host' property of a dax_device that can be used for this purpose. It is
a free form string, but for a dax_device associated with a block device
it is the bdev name.
This is a stop-gap until filesystems are able to mount on a dax-inode
directly.
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
Changes since v2:
* fixed slab corruption due to non-null dax_dev->host at
dax_i_callback() time
drivers/dax/dax.h | 2 +
drivers/dax/device.c | 2 +
drivers/dax/super.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++--
include/linux/dax.h | 1 +
4 files changed, 86 insertions(+), 6 deletions(-)
diff --git a/drivers/dax/dax.h b/drivers/dax/dax.h
index 2472d9da96db..246a24d68d4c 100644
--- a/drivers/dax/dax.h
+++ b/drivers/dax/dax.h
@@ -13,7 +13,7 @@
#ifndef __DAX_H__
#define __DAX_H__
struct dax_device;
-struct dax_device *alloc_dax(void *private);
+struct dax_device *alloc_dax(void *private, const char *host);
void put_dax(struct dax_device *dax_dev);
bool dax_alive(struct dax_device *dax_dev);
void kill_dax(struct dax_device *dax_dev);
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 19a42edbfa03..db68f4fa8ce0 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -645,7 +645,7 @@ struct dev_dax *devm_create_dev_dax(struct dax_region *dax_region,
goto err_id;
}
- dax_dev = alloc_dax(dev_dax);
+ dax_dev = alloc_dax(dev_dax, NULL);
if (!dax_dev)
goto err_dax;
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index c9f85f1c086e..8d446674c1da 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -30,6 +30,10 @@ 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);
@@ -46,12 +50,15 @@ EXPORT_SYMBOL_GPL(dax_read_unlock);
* struct dax_device - anchor object for dax services
* @inode: core vfs
* @cdev: optional character interface for "device dax"
+ * @host: optional name for lookups where the device path is not available
* @private: dax driver private data
* @alive: !alive + rcu grace period == no new operations / mappings
*/
struct dax_device {
+ struct hlist_node list;
struct inode inode;
struct cdev cdev;
+ const char *host;
void *private;
bool alive;
};
@@ -63,6 +70,11 @@ bool dax_alive(struct dax_device *dax_dev)
}
EXPORT_SYMBOL_GPL(dax_alive);
+static int dax_host_hash(const char *host)
+{
+ return hashlen_hash(hashlen_string("DAX", host)) % DAX_HASH_SIZE;
+}
+
/*
* Note, rcu is not protecting the liveness of dax_dev, rcu is ensuring
* that any fault handlers or operations that might have seen
@@ -75,7 +87,13 @@ void kill_dax(struct dax_device *dax_dev)
return;
dax_dev->alive = false;
+
synchronize_srcu(&dax_srcu);
+
+ spin_lock(&dax_host_lock);
+ hlist_del_init(&dax_dev->list);
+ spin_unlock(&dax_host_lock);
+
dax_dev->private = NULL;
}
EXPORT_SYMBOL_GPL(kill_dax);
@@ -98,6 +116,8 @@ static void dax_i_callback(struct rcu_head *head)
struct inode *inode = container_of(head, struct inode, i_rcu);
struct dax_device *dax_dev = to_dax_dev(inode);
+ kfree(dax_dev->host);
+ dax_dev->host = NULL;
ida_simple_remove(&dax_minor_ida, MINOR(inode->i_rdev));
kmem_cache_free(dax_cache, dax_dev);
}
@@ -169,26 +189,53 @@ static struct dax_device *dax_dev_get(dev_t devt)
return dax_dev;
}
-struct dax_device *alloc_dax(void *private)
+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)
{
struct dax_device *dax_dev;
+ const char *host;
dev_t devt;
int minor;
+ host = kstrdup(__host, GFP_KERNEL);
+ if (__host && !host)
+ return NULL;
+
minor = ida_simple_get(&dax_minor_ida, 0, nr_dax, GFP_KERNEL);
if (minor < 0)
- return NULL;
+ goto err_minor;
devt = MKDEV(MAJOR(dax_devt), minor);
dax_dev = dax_dev_get(devt);
if (!dax_dev)
- goto err_inode;
+ goto err_dev;
+ dax_add_host(dax_dev, host);
dax_dev->private = private;
return dax_dev;
- err_inode:
+ err_dev:
ida_simple_remove(&dax_minor_ida, minor);
+ err_minor:
+ kfree(host);
return NULL;
}
EXPORT_SYMBOL_GPL(alloc_dax);
@@ -202,6 +249,38 @@ void put_dax(struct dax_device *dax_dev)
EXPORT_SYMBOL_GPL(put_dax);
/**
+ * dax_get_by_host() - temporary lookup mechanism for filesystem-dax
+ * @host: alternate name for the device registered by a dax driver
+ */
+struct dax_device *dax_get_by_host(const char *host)
+{
+ struct dax_device *dax_dev, *found = NULL;
+ int hash, id;
+
+ if (!host)
+ 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_read_unlock(id);
+
+ return found;
+}
+EXPORT_SYMBOL_GPL(dax_get_by_host);
+
+/**
* inode_dax: convert a public inode into its dax_dev
* @inode: An inode with i_cdev pointing to a dax_dev
*
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 5b62f5d19aea..9b2d5ba10d7d 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -10,6 +10,7 @@ struct iomap_ops;
int dax_read_lock(void);
void dax_read_unlock(int id);
+struct dax_device *dax_get_by_host(const char *host);
/*
* We use lowest available bit in exceptional entry for locking, one bit for
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