Commit 2bcbeaef authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jason Gunthorpe
Browse files

mm/hmm: always return EBUSY for invalid ranges in hmm_range_{fault,snapshot} 

We should not have two different error codes for the same
condition. EAGAIN must be reserved for the FAULT_FLAG_ALLOW_RETRY retry
case and signals to the caller that the mmap_sem has been unlocked.

Use EBUSY for the !valid case so that callers can get the locking right.

Link: https://lore.kernel.org/r/20190724065258.16603-2-hch@lst.de


Tested-by: default avatarRalph Campbell <rcampbell@nvidia.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarRalph Campbell <rcampbell@nvidia.com>
Reviewed-by: default avatarJason Gunthorpe <jgg@mellanox.com>
Reviewed-by: default avatarFelix Kuehling <Felix.Kuehling@amd.com>
[jgg: elaborated commit message]
Signed-off-by: default avatarJason Gunthorpe <jgg@mellanox.com>
parent 5f9e832c

Documentation/vm/hmm.rst

+1 −1
Original line number Diff line number Diff line
@@ -237,7 +237,7 @@ The usage pattern is:: 
      ret = hmm_range_snapshot(&range);

      if (ret) {

          up_read(&mm->mmap_sem);

          if (ret == -EAGAIN) {

          if (ret == -EBUSY) {

            /*

             * No need to check hmm_range_wait_until_valid() return value

             * on retry we will get proper error with hmm_range_snapshot()

mm/hmm.c

+4 −6
Original line number Diff line number Diff line
@@ -946,7 +946,7 @@ EXPORT_SYMBOL(hmm_range_unregister); 
 * @range: range

 * Return: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid

 *          permission (for instance asking for write and range is read only),

 *          -EAGAIN if you need to retry, -EFAULT invalid (ie either no valid

 *          -EBUSY if you need to retry, -EFAULT invalid (ie either no valid

 *          vma or it is illegal to access that range), number of valid pages

 *          in range->pfns[] (from range start address).

 *
@@ -967,7 +967,7 @@ long hmm_range_snapshot(struct hmm_range *range) 
	do {

		/* If range is no longer valid force retry. */

		if (!range->valid)

			return -EAGAIN;

			return -EBUSY;



		vma = find_vma(hmm->mm, start);

		if (vma == NULL || (vma->vm_flags & device_vma))
@@ -1062,10 +1062,8 @@ long hmm_range_fault(struct hmm_range *range, bool block) 


	do {

		/* If range is no longer valid force retry. */

		if (!range->valid) {

			up_read(&hmm->mm->mmap_sem);

			return -EAGAIN;

		}

		if (!range->valid)

			return -EBUSY;



		vma = find_vma(hmm->mm, start);

		if (vma == NULL || (vma->vm_flags & device_vma))