On 8/26/20 8:24 AM, Christoph Hellwig wrote:
None of the complicated overlapping regions bits of the kobj_map are
required for the character device lookup, so just a trivial xarray
instead.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
fs/char_dev.c | 94 +++++++++++++++++++++++++--------------------------
fs/dcache.c | 1 -
fs/internal.h | 5 ---
3 files changed, 46 insertions(+), 54 deletions(-)
diff --git a/fs/char_dev.c b/fs/char_dev.c
index ba0ded7842a779..6c4d6c4938f14b 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -17,7 +17,6 @@
#include <linux/seq_file.h>
#include <linux/kobject.h>
-#include <linux/kobj_map.h>
#include <linux/cdev.h>
#include <linux/mutex.h>
#include <linux/backing-dev.h>
@@ -25,8 +24,7 @@
#include "internal.h"
-static struct kobj_map *cdev_map;
-
+static DEFINE_XARRAY(cdev_map);
static DEFINE_MUTEX(chrdevs_lock);
#define CHRDEV_MAJOR_HASH_SIZE 255
@@ -367,6 +365,29 @@ void cdev_put(struct cdev *p)
}
}
+static struct cdev *cdev_lookup(dev_t dev)
+{
+ struct cdev *cdev;
+
+retry:
+ mutex_lock(&chrdevs_lock);
+ cdev = xa_load(&cdev_map, dev);
+ if (!cdev) {
+ mutex_unlock(&chrdevs_lock);
+
+ if (request_module("char-major-%d-%d",
+ MAJOR(dev), MINOR(dev)) > 0)
+ /* Make old-style 2.4 aliases work */
+ request_module("char-major-%d", MAJOR(dev));
+ goto retry;
+ }
+
+ if (!cdev_get(cdev))
+ cdev = NULL;
+ mutex_unlock(&chrdevs_lock);
+ return cdev;
+}
+
/*
* Called every time a character special file is opened
*/
@@ -380,13 +401,10 @@ static int chrdev_open(struct inode *inode, struct file *filp)
spin_lock(&cdev_lock);
p = inode->i_cdev;
if (!p) {
- struct kobject *kobj;
- int idx;
spin_unlock(&cdev_lock);
- kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
- if (!kobj)
+ new = cdev_lookup(inode->i_rdev);
+ if (!new)
return -ENXIO;
- new = container_of(kobj, struct cdev, kobj);
spin_lock(&cdev_lock);
/* Check i_cdev again in case somebody beat us to it while
we dropped the lock. */
@@ -454,18 +472,6 @@ const struct file_operations def_chr_fops = {
.llseek = noop_llseek,
};
-static struct kobject *exact_match(dev_t dev, int *part, void *data)
-{
- struct cdev *p = data;
- return &p->kobj;
-}
-
-static int exact_lock(dev_t dev, void *data)
-{
- struct cdev *p = data;
- return cdev_get(p) ? 0 : -1;
-}
-
/**
* cdev_add() - add a char device to the system
* @p: the cdev structure for the device
@@ -478,7 +484,7 @@ static int exact_lock(dev_t dev, void *data)
*/
int cdev_add(struct cdev *p, dev_t dev, unsigned count)
{
- int error;
+ int error, i;
p->dev = dev;
p->count = count;
@@ -486,14 +492,22 @@ int cdev_add(struct cdev *p, dev_t dev, unsigned count)
if (WARN_ON(dev == WHITEOUT_DEV))
return -EBUSY;
- error = kobj_map(cdev_map, dev, count, NULL,
- exact_match, exact_lock, p);
- if (error)
- return error;
+ mutex_lock(&chrdevs_lock);
+ for (i = 0; i < count; i++) {
+ error = xa_insert(&cdev_map, dev + i, p, GFP_KERNEL);
+ if (error)
+ goto out_unwind;
+ }
+ mutex_unlock(&chrdevs_lock);
kobject_get(p->kobj.parent);
-
return 0;
+
+out_unwind:
+ while (--i >= 0)
+ xa_erase(&cdev_map, dev + i);
+ mutex_unlock(&chrdevs_lock);
+ return error;
}
/**
Do you really need the mutex?
Wouldn't xa_store_range() be better and avoid the mutex?
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Felix Imendörffer
