Introduce a new noio flag to indicate to get_user_pages to use the
FOLL_FAST_ONLY flag. This will cause get_user_pages to fail when it
would otherwise fault in a page.
Currently, the noio flag is only checked in iov_iter_get_pages and
iov_iter_get_pages_alloc. This is enough for iomaop_dio_rw, but it
may make sense to check for this flag in other contexts as well.
Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
---
include/linux/uio.h | 1 +
lib/iov_iter.c | 20 +++++++++++++++-----
2 files changed, 16 insertions(+), 5 deletions(-)
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 152b3605e86c..8de6354ade14 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -29,6 +29,7 @@ enum iter_type {
struct iov_iter {
u8 iter_type;
+ bool noio;
bool data_source;
size_t iov_offset;
size_t count;
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 7221665f7ac4..a20426cedf60 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -509,6 +509,7 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
WARN_ON(direction & ~(READ | WRITE));
*i = (struct iov_iter) {
.iter_type = ITER_IOVEC,
+ .noio = false,
.data_source = direction,
.iov = iov,
.nr_segs = nr_segs,
@@ -1519,13 +1520,17 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
return 0;
if (likely(iter_is_iovec(i))) {
+ unsigned int gup_flags = 0;
unsigned long addr;
+ if (iov_iter_rw(i) != WRITE)
+ gup_flags |= FOLL_WRITE;
+ if (i->noio)
+ gup_flags |= FOLL_FAST_ONLY;
+
addr = first_iovec_segment(i, &len, start, maxsize, maxpages);
n = DIV_ROUND_UP(len, PAGE_SIZE);
- res = get_user_pages_fast(addr, n,
- iov_iter_rw(i) != WRITE ? FOLL_WRITE : 0,
- pages);
+ res = get_user_pages_fast(addr, n, gup_flags, pages);
if (unlikely(res <= 0))
return res;
return (res == n ? len : res * PAGE_SIZE) - *start;
@@ -1641,15 +1646,20 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
return 0;
if (likely(iter_is_iovec(i))) {
+ unsigned int gup_flags = 0;
unsigned long addr;
+ if (iov_iter_rw(i) != WRITE)
+ gup_flags |= FOLL_WRITE;
+ if (i->noio)
+ gup_flags |= FOLL_FAST_ONLY;
+
addr = first_iovec_segment(i, &len, start, maxsize, ~0U);
n = DIV_ROUND_UP(len, PAGE_SIZE);
p = get_pages_array(n);
if (!p)
return -ENOMEM;
- res = get_user_pages_fast(addr, n,
- iov_iter_rw(i) != WRITE ? FOLL_WRITE : 0, p);
+ res = get_user_pages_fast(addr, n, gup_flags, p);
if (unlikely(res <= 0)) {
kvfree(p);
*pages = ZERO_SIZE_PTR;
--
2.26.3
