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| author | Andreas Gruenbacher <agruenba@redhat.com> | 2021-07-12 12:06:14 +0200 |
|---|---|---|
| committer | Andreas Gruenbacher <agruenba@redhat.com> | 2021-10-24 15:26:06 +0200 |
| commit | 3337ab08d08b1a375f88471d9c8b1cac968cb054 (patch) | |
| tree | d59b8bcd05c76e7f7924a4d9eb587e3e2791b268 /lib/iov_iter.c | |
| parent | 55b8fe703bc51200d4698596c90813453b35ae63 (diff) | |
| download | lwn-3337ab08d08b1a375f88471d9c8b1cac968cb054.tar.gz lwn-3337ab08d08b1a375f88471d9c8b1cac968cb054.zip | |
iov_iter: Introduce nofault flag to disable page faults
Introduce a new nofault flag to indicate to iov_iter_get_pages not to
fault in user pages.
This is implemented by passing the FOLL_NOFAULT flag to get_user_pages,
which causes get_user_pages to fail when it would otherwise fault in a
page. We'll use the ->nofault flag to prevent iomap_dio_rw from faulting
in pages when page faults are not allowed.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Diffstat (limited to 'lib/iov_iter.c')
| -rw-r--r-- | lib/iov_iter.c | 20 |
1 files changed, 15 insertions, 5 deletions
diff --git a/lib/iov_iter.c b/lib/iov_iter.c index ac9a87e727a3..66a740e6e153 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -513,6 +513,7 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction, WARN_ON(direction & ~(READ | WRITE)); *i = (struct iov_iter) { .iter_type = ITER_IOVEC, + .nofault = false, .data_source = direction, .iov = iov, .nr_segs = nr_segs, @@ -1527,13 +1528,17 @@ 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->nofault) + gup_flags |= FOLL_NOFAULT; + 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; @@ -1649,15 +1654,20 @@ 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->nofault) + gup_flags |= FOLL_NOFAULT; + 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 = NULL; |