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: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
[jgg: elaborated commit message]
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
diff --git a/mm/hmm.c b/mm/hmm.c
index e1eedef..16b6731 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -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/* If range is no longer valid force retry.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/* If range is no longer valid force retry.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))