IB/uverbs: BKL is not needed for ib_uverbs_open()
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>
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1 changed files with 13 additions and 7 deletions
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@ -45,7 +45,6 @@
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#include <linux/file.h>
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#include <linux/mount.h>
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#include <linux/cdev.h>
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#include <linux/smp_lock.h>
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#include <asm/uaccess.h>
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@ -611,23 +610,32 @@ static int ib_uverbs_mmap(struct file *filp, struct vm_area_struct *vma)
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return file->device->ib_dev->mmap(file->ucontext, vma);
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}
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/*
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* ib_uverbs_open() does not need the BKL:
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*
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* - dev_table[] accesses are protected by map_lock, the
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* ib_uverbs_device structures are properly reference counted, and
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* everything else is purely local to the file being created, so
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* races against other open calls are not a problem;
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* - there is no ioctl method to race against;
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* - the device is added to dev_table[] as the last part of module
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* initialization, the open method will either immediately run
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* -ENXIO, or all required initialization will be done.
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*/
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static int ib_uverbs_open(struct inode *inode, struct file *filp)
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{
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struct ib_uverbs_device *dev;
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struct ib_uverbs_file *file;
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int ret;
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lock_kernel();
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spin_lock(&map_lock);
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dev = dev_table[iminor(inode) - IB_UVERBS_BASE_MINOR];
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if (dev)
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kref_get(&dev->ref);
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spin_unlock(&map_lock);
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if (!dev) {
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unlock_kernel();
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if (!dev)
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return -ENXIO;
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}
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if (!try_module_get(dev->ib_dev->owner)) {
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ret = -ENODEV;
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@ -648,7 +656,6 @@ static int ib_uverbs_open(struct inode *inode, struct file *filp)
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filp->private_data = file;
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unlock_kernel();
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return 0;
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err_module:
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@ -656,7 +663,6 @@ err_module:
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err:
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kref_put(&dev->ref, ib_uverbs_release_dev);
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unlock_kernel();
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return ret;
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}
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