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>
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@ -35,6 +35,7 @@ struct iov_iter_state {
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struct iov_iter {
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struct iov_iter {
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u8 iter_type;
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u8 iter_type;
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bool nofault;
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bool data_source;
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bool data_source;
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size_t iov_offset;
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size_t iov_offset;
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size_t count;
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size_t count;
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@ -513,6 +513,7 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
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WARN_ON(direction & ~(READ | WRITE));
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WARN_ON(direction & ~(READ | WRITE));
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*i = (struct iov_iter) {
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*i = (struct iov_iter) {
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.iter_type = ITER_IOVEC,
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.iter_type = ITER_IOVEC,
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.nofault = false,
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.data_source = direction,
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.data_source = direction,
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.iov = iov,
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.iov = iov,
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.nr_segs = nr_segs,
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.nr_segs = nr_segs,
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@ -1527,13 +1528,17 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
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return 0;
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return 0;
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if (likely(iter_is_iovec(i))) {
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if (likely(iter_is_iovec(i))) {
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unsigned int gup_flags = 0;
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unsigned long addr;
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unsigned long addr;
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if (iov_iter_rw(i) != WRITE)
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gup_flags |= FOLL_WRITE;
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if (i->nofault)
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gup_flags |= FOLL_NOFAULT;
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addr = first_iovec_segment(i, &len, start, maxsize, maxpages);
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addr = first_iovec_segment(i, &len, start, maxsize, maxpages);
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n = DIV_ROUND_UP(len, PAGE_SIZE);
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n = DIV_ROUND_UP(len, PAGE_SIZE);
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res = get_user_pages_fast(addr, n,
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res = get_user_pages_fast(addr, n, gup_flags, pages);
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iov_iter_rw(i) != WRITE ? FOLL_WRITE : 0,
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pages);
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if (unlikely(res <= 0))
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if (unlikely(res <= 0))
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return res;
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return res;
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return (res == n ? len : res * PAGE_SIZE) - *start;
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return (res == n ? len : res * PAGE_SIZE) - *start;
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@ -1649,15 +1654,20 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
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return 0;
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return 0;
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if (likely(iter_is_iovec(i))) {
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if (likely(iter_is_iovec(i))) {
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unsigned int gup_flags = 0;
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unsigned long addr;
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unsigned long addr;
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if (iov_iter_rw(i) != WRITE)
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gup_flags |= FOLL_WRITE;
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if (i->nofault)
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gup_flags |= FOLL_NOFAULT;
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addr = first_iovec_segment(i, &len, start, maxsize, ~0U);
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addr = first_iovec_segment(i, &len, start, maxsize, ~0U);
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n = DIV_ROUND_UP(len, PAGE_SIZE);
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n = DIV_ROUND_UP(len, PAGE_SIZE);
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p = get_pages_array(n);
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p = get_pages_array(n);
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if (!p)
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if (!p)
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return -ENOMEM;
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return -ENOMEM;
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res = get_user_pages_fast(addr, n,
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res = get_user_pages_fast(addr, n, gup_flags, p);
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iov_iter_rw(i) != WRITE ? FOLL_WRITE : 0, p);
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if (unlikely(res <= 0)) {
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if (unlikely(res <= 0)) {
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kvfree(p);
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kvfree(p);
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*pages = NULL;
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*pages = NULL;
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