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

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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>
This commit is contained in:
Christoph Hellwig 2019-07-24 08:52:52 +02:00 committed by Jason Gunthorpe
parent 5f9e832c13
commit 2bcbeaefde
2 changed files with 5 additions and 7 deletions
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2
Documentation/vm/hmm.rst
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@ -237,7 +237,7 @@ The usage pattern is::
ret = hmm_range_snapshot(&range); ret = hmm_range_snapshot(&range);
if (ret) { if (ret) {
up_read(&mm->mmap_sem); up_read(&mm->mmap_sem);
if (ret == -EAGAIN) { if (ret == -EBUSY) {
/* /*
* No need to check hmm_range_wait_until_valid() return value * No need to check hmm_range_wait_until_valid() return value
* on retry we will get proper error with hmm_range_snapshot() * on retry we will get proper error with hmm_range_snapshot()

10
mm/hmm.c
View File

@ -946,7 +946,7 @@ EXPORT_SYMBOL(hmm_range_unregister);
* @range: range * @range: range
* Return: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid * Return: -EINVAL if invalid argument, -ENOMEM out of memory, -EPERM invalid
* permission (for instance asking for write and range is read only), * 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 * vma or it is illegal to access that range), number of valid pages
* in range->pfns[] (from range start address). * in range->pfns[] (from range start address).
* *
@ -967,7 +967,7 @@ long hmm_range_snapshot(struct hmm_range *range)
do { do {
/* If range is no longer valid force retry. */ /* If range is no longer valid force retry. */
if (!range->valid) if (!range->valid)
return -EAGAIN; return -EBUSY;
vma = find_vma(hmm->mm, start); vma = find_vma(hmm->mm, start);
if (vma == NULL || (vma->vm_flags & device_vma)) if (vma == NULL || (vma->vm_flags & device_vma))
@ -1062,10 +1062,8 @@ long hmm_range_fault(struct hmm_range *range, bool block)
do { do {
/* If range is no longer valid force retry. */ /* If range is no longer valid force retry. */
if (!range->valid) { if (!range->valid)
up_read(&hmm->mm->mmap_sem); return -EBUSY;
return -EAGAIN;
}
vma = find_vma(hmm->mm, start); vma = find_vma(hmm->mm, start);
if (vma == NULL || (vma->vm_flags & device_vma)) if (vma == NULL || (vma->vm_flags & device_vma))