This code was using get_user_pages*(), in a "Case 2" scenario
(DMA/RDMA), using the categorization from [1]. That means that it's
time to convert the get_user_pages*() + put_page() calls to
pin_user_pages*() + unpin_user_pages() calls.
There is some helpful background in [2]: basically, this is a small
part of fixing a long-standing disconnect between pinning pages, and
file systems' use of those pages.
Note that this effectively changes the code's behavior as well: it now
ultimately calls set_page_dirty_lock(), instead of SetPageDirty(). This
is probably more accurate.
As Christoph Hellwig put it, "set_page_dirty() is only safe if we are
dealing with a file backed page where we have reference on the inode it
hangs off." [3]
[1] Documentation/core-api/pin_user_pages.rst
[2] "Explicit pinning of user-space pages":
https://lwn.net/Articles/807108/
[3] https://lore.kernel.org/r/20190723153640.gb...@lst.de
Signed-off-by: John Hubbard <jhubb...@nvidia.com>
---
Hi,
Note that I have only compile-tested this patch, although that does
also include cross-compiling for a few other arches.
thanks,
John Hubbard
NVIDIA
drivers/misc/mic/scif/scif_rma.c | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/drivers/misc/mic/scif/scif_rma.c b/drivers/misc/mic/scif/scif_rma.c
index 01e27682ea30..406cd5abfa72 100644
--- a/drivers/misc/mic/scif/scif_rma.c
+++ b/drivers/misc/mic/scif/scif_rma.c
@@ -113,14 +113,17 @@ static int scif_destroy_pinned_pages(struct
scif_pinned_pages *pin)
int writeable = pin->prot & SCIF_PROT_WRITE;
int kernel = SCIF_MAP_KERNEL & pin->map_flags;
- for (j = 0; j < pin->nr_pages; j++) {
- if (pin->pages[j] && !kernel) {
- if (writeable)
- SetPageDirty(pin->pages[j]);
- put_page(pin->pages[j]);
+ if (kernel) {
+ for (j = 0; j < pin->nr_pages; j++) {
+ if (pin->pages[j] && !kernel) {
+ if (writeable)
+ set_page_dirty_lock(pin->pages[j]);
+ put_page(pin->pages[j]);
+ }
}
- }
-
+ } else
+ unpin_user_pages_dirty_lock(pin->pages, pin->nr_pages,
+ writeable);
scif_free(pin->pages,
pin->nr_pages * sizeof(*pin->pages));
scif_free(pin, sizeof(*pin));
@@ -1375,7 +1378,7 @@ int __scif_pin_pages(void *addr, size_t len, int
*out_prot,
}
}
- pinned_pages->nr_pages = get_user_pages_fast(
+ pinned_pages->nr_pages = pin_user_pages_fast(
(u64)addr,
nr_pages,
(prot & SCIF_PROT_WRITE) ? FOLL_WRITE : 0,
@@ -1385,11 +1388,8 @@ int __scif_pin_pages(void *addr, size_t len, int
*out_prot,
if (ulimit)
__scif_dec_pinned_vm_lock(mm, nr_pages);
/* Roll back any pinned pages */
- for (i = 0; i < pinned_pages->nr_pages; i++) {
- if (pinned_pages->pages[i])
- put_page(
- pinned_pages->pages[i]);
- }
+ unpin_user_pages(pinned_pages->pages,
+ pinned_pages->nr_pages);
prot &= ~SCIF_PROT_WRITE;
try_upgrade = false;
goto retry;
--
2.26.2
