mm/hmm: remove HMM_FAULT_SNAPSHOT
Now that flags are handled on a fine-grained per-page basis this global
flag is redundant and has a confusing overlap with the pfn_flags_mask and
default_flags.
Normalize the HMM_FAULT_SNAPSHOT behavior into one place. Callers needing
the SNAPSHOT behavior should set a pfn_flags_mask and default_flags that
always results in a cleared HMM_PFN_VALID. Then no pages will be faulted,
and HMM_FAULT_SNAPSHOT is not a special flow that overrides the masking
mechanism.
As this is the last flag, also remove the flags argument. If future flags
are needed they can be part of the struct hmm_range function arguments.
Link: https://lore.kernel.org/r/20200327200021.29372-5-jgg@ziepe.ca
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst
index 95fec59..4e3e936 100644
--- a/Documentation/vm/hmm.rst
+++ b/Documentation/vm/hmm.rst
@@ -161,13 +161,11 @@
When the device driver wants to populate a range of virtual addresses, it can
use::
- long hmm_range_fault(struct hmm_range *range, unsigned int flags);
+ long hmm_range_fault(struct hmm_range *range);
-With the HMM_RANGE_SNAPSHOT flag, it will only fetch present CPU page table
-entries and will not trigger a page fault on missing or non-present entries.
-Without that flag, it does trigger a page fault on missing or read-only entries
-if write access is requested (see below). Page faults use the generic mm page
-fault code path just like a CPU page fault.
+It will trigger a page fault on missing or read-only entries if write access is
+requested (see below). Page faults use the generic mm page fault code path just
+like a CPU page fault.
Both functions copy CPU page table entries into their pfns array argument. Each
entry in that array corresponds to an address in the virtual range. HMM
@@ -197,7 +195,7 @@
again:
range.notifier_seq = mmu_interval_read_begin(&interval_sub);
down_read(&mm->mmap_sem);
- ret = hmm_range_fault(&range, HMM_RANGE_SNAPSHOT);
+ ret = hmm_range_fault(&range);
if (ret) {
up_read(&mm->mmap_sem);
if (ret == -EBUSY)
