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IB/uverbs: BKL is not needed for ib_uverbs_open()

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Remove explicit lock_kernel() calls and document why the code is safe.

Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Roland Dreier 2008-06-27 14:43:20 -07:00 committed by Jonathan Corbet
parent 57debddaa1
commit 5b2d281acb
1 changed files with 13 additions and 7 deletions
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20
drivers/infiniband/core/uverbs_main.c
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@ -45,7 +45,6 @@
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/cdev.h>
#include <linux/smp_lock.h>
#include <asm/uaccess.h>
@ -611,23 +610,32 @@ static int ib_uverbs_mmap(struct file *filp, struct vm_area_struct *vma)
return file->device->ib_dev->mmap(file->ucontext, vma);
}
/*
* ib_uverbs_open() does not need the BKL:
*
* - dev_table[] accesses are protected by map_lock, the
* ib_uverbs_device structures are properly reference counted, and
* everything else is purely local to the file being created, so
* races against other open calls are not a problem;
* - there is no ioctl method to race against;
* - the device is added to dev_table[] as the last part of module
* initialization, the open method will either immediately run
* -ENXIO, or all required initialization will be done.
*/
static int ib_uverbs_open(struct inode *inode, struct file *filp)
{
struct ib_uverbs_device *dev;
struct ib_uverbs_file *file;
int ret;
lock_kernel();
spin_lock(&map_lock);
dev = dev_table[iminor(inode) - IB_UVERBS_BASE_MINOR];
if (dev)
kref_get(&dev->ref);
spin_unlock(&map_lock);
if (!dev) {
unlock_kernel();
if (!dev)
return -ENXIO;
}
if (!try_module_get(dev->ib_dev->owner)) {
ret = -ENODEV;
@ -648,7 +656,6 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp)
filp->private_data = file;
unlock_kernel();
return 0;
err_module:
@ -656,7 +663,6 @@ err_module:
err:
kref_put(&dev->ref, ib_uverbs_release_dev);
unlock_kernel();
return ret;
}