From fcb14cb1bdacec5b4374fe161e83fb8208164a85 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sun, 22 May 2022 14:59:25 -0400 Subject: new iov_iter flavour - ITER_UBUF Equivalent of single-segment iovec. Initialized by iov_iter_ubuf(), checked for by iter_is_ubuf(), otherwise behaves like ITER_IOVEC ones. We are going to expose the things like ->write_iter() et.al. to those in subsequent commits. New predicate (user_backed_iter()) that is true for ITER_IOVEC and ITER_UBUF; places like direct-IO handling should use that for checking that pages we modify after getting them from iov_iter_get_pages() would need to be dirtied. DO NOT assume that replacing iter_is_iovec() with user_backed_iter() will solve all problems - there's code that uses iter_is_iovec() to decide how to poke around in iov_iter guts and for that the predicate replacement obviously won't suffice. Signed-off-by: Al Viro --- lib/iov_iter.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 69 insertions(+), 18 deletions(-) (limited to 'lib') diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 0e0be334dbee..b3493d20536e 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -16,6 +16,16 @@ #define PIPE_PARANOIA /* for now */ +/* covers ubuf and kbuf alike */ +#define iterate_buf(i, n, base, len, off, __p, STEP) { \ + size_t __maybe_unused off = 0; \ + len = n; \ + base = __p + i->iov_offset; \ + len -= (STEP); \ + i->iov_offset += len; \ + n = len; \ +} + /* covers iovec and kvec alike */ #define iterate_iovec(i, n, base, len, off, __p, STEP) { \ size_t off = 0; \ @@ -110,7 +120,12 @@ __out: \ if (unlikely(i->count < n)) \ n = i->count; \ if (likely(n)) { \ - if (likely(iter_is_iovec(i))) { \ + if (likely(iter_is_ubuf(i))) { \ + void __user *base; \ + size_t len; \ + iterate_buf(i, n, base, len, off, \ + i->ubuf, (I)) \ + } else if (likely(iter_is_iovec(i))) { \ const struct iovec *iov = i->iov; \ void __user *base; \ size_t len; \ @@ -275,7 +290,11 @@ out: */ size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t size) { - if (iter_is_iovec(i)) { + if (iter_is_ubuf(i)) { + size_t n = min(size, iov_iter_count(i)); + n -= fault_in_readable(i->ubuf + i->iov_offset, n); + return size - n; + } else if (iter_is_iovec(i)) { size_t count = min(size, iov_iter_count(i)); const struct iovec *p; size_t skip; @@ -314,7 +333,11 @@ EXPORT_SYMBOL(fault_in_iov_iter_readable); */ size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t size) { - if (iter_is_iovec(i)) { + if (iter_is_ubuf(i)) { + size_t n = min(size, iov_iter_count(i)); + n -= fault_in_safe_writeable(i->ubuf + i->iov_offset, n); + return size - n; + } else if (iter_is_iovec(i)) { size_t count = min(size, iov_iter_count(i)); const struct iovec *p; size_t skip; @@ -345,6 +368,7 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction, *i = (struct iov_iter) { .iter_type = ITER_IOVEC, .nofault = false, + .user_backed = true, .data_source = direction, .iov = iov, .nr_segs = nr_segs, @@ -494,7 +518,7 @@ size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i) { if (unlikely(iov_iter_is_pipe(i))) return copy_pipe_to_iter(addr, bytes, i); - if (iter_is_iovec(i)) + if (user_backed_iter(i)) might_fault(); iterate_and_advance(i, bytes, base, len, off, copyout(base, addr + off, len), @@ -583,7 +607,7 @@ size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i) { if (unlikely(iov_iter_is_pipe(i))) return copy_mc_pipe_to_iter(addr, bytes, i); - if (iter_is_iovec(i)) + if (user_backed_iter(i)) might_fault(); __iterate_and_advance(i, bytes, base, len, off, copyout_mc(base, addr + off, len), @@ -601,7 +625,7 @@ size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i) WARN_ON(1); return 0; } - if (iter_is_iovec(i)) + if (user_backed_iter(i)) might_fault(); iterate_and_advance(i, bytes, base, len, off, copyin(addr + off, base, len), @@ -894,16 +918,16 @@ void iov_iter_advance(struct iov_iter *i, size_t size) { if (unlikely(i->count < size)) size = i->count; - if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) { + if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i))) { + i->iov_offset += size; + i->count -= size; + } else if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) { /* iovec and kvec have identical layouts */ iov_iter_iovec_advance(i, size); } else if (iov_iter_is_bvec(i)) { iov_iter_bvec_advance(i, size); } else if (iov_iter_is_pipe(i)) { pipe_advance(i, size); - } else if (unlikely(iov_iter_is_xarray(i))) { - i->iov_offset += size; - i->count -= size; } else if (iov_iter_is_discard(i)) { i->count -= size; } @@ -950,7 +974,7 @@ void iov_iter_revert(struct iov_iter *i, size_t unroll) return; } unroll -= i->iov_offset; - if (iov_iter_is_xarray(i)) { + if (iov_iter_is_xarray(i) || iter_is_ubuf(i)) { BUG(); /* We should never go beyond the start of the specified * range since we might then be straying into pages that * aren't pinned. @@ -1158,6 +1182,14 @@ static bool iov_iter_aligned_bvec(const struct iov_iter *i, unsigned addr_mask, bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask, unsigned len_mask) { + if (likely(iter_is_ubuf(i))) { + if (i->count & len_mask) + return false; + if ((unsigned long)(i->ubuf + i->iov_offset) & addr_mask) + return false; + return true; + } + if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) return iov_iter_aligned_iovec(i, addr_mask, len_mask); @@ -1233,6 +1265,13 @@ static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i) unsigned long iov_iter_alignment(const struct iov_iter *i) { + if (likely(iter_is_ubuf(i))) { + size_t size = i->count; + if (size) + return ((unsigned long)i->ubuf + i->iov_offset) | size; + return 0; + } + /* iovec and kvec have identical layouts */ if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) return iov_iter_alignment_iovec(i); @@ -1263,6 +1302,9 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i) size_t size = i->count; unsigned k; + if (iter_is_ubuf(i)) + return 0; + if (WARN_ON(!iter_is_iovec(i))) return ~0U; @@ -1385,12 +1427,15 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i, return min_t(size_t, nr * PAGE_SIZE - offset, maxsize); } -/* must be done on non-empty ITER_IOVEC one */ +/* must be done on non-empty ITER_UBUF or ITER_IOVEC one */ static unsigned long first_iovec_segment(const struct iov_iter *i, size_t *size) { size_t skip; long k; + if (iter_is_ubuf(i)) + return (unsigned long)i->ubuf + i->iov_offset; + for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) { size_t len = i->iov[k].iov_len - skip; @@ -1432,7 +1477,7 @@ ssize_t iov_iter_get_pages(struct iov_iter *i, if (maxsize > MAX_RW_COUNT) maxsize = MAX_RW_COUNT; - if (likely(iter_is_iovec(i))) { + if (likely(user_backed_iter(i))) { unsigned int gup_flags = 0; unsigned long addr; @@ -1559,7 +1604,7 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, if (maxsize > MAX_RW_COUNT) maxsize = MAX_RW_COUNT; - if (likely(iter_is_iovec(i))) { + if (likely(user_backed_iter(i))) { unsigned int gup_flags = 0; unsigned long addr; @@ -1715,6 +1760,11 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages) { if (unlikely(!i->count)) return 0; + if (likely(iter_is_ubuf(i))) { + unsigned offs = offset_in_page(i->ubuf + i->iov_offset); + int npages = DIV_ROUND_UP(offs + i->count, PAGE_SIZE); + return min(npages, maxpages); + } /* iovec and kvec have identical layouts */ if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) return iov_npages(i, maxpages); @@ -1749,17 +1799,16 @@ const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags) WARN_ON(1); return NULL; } - if (unlikely(iov_iter_is_discard(new) || iov_iter_is_xarray(new))) - return NULL; if (iov_iter_is_bvec(new)) return new->bvec = kmemdup(new->bvec, new->nr_segs * sizeof(struct bio_vec), flags); - else + else if (iov_iter_is_kvec(new) || iter_is_iovec(new)) /* iovec and kvec have identical layout */ return new->iov = kmemdup(new->iov, new->nr_segs * sizeof(struct iovec), flags); + return NULL; } EXPORT_SYMBOL(dup_iter); @@ -1953,10 +2002,12 @@ EXPORT_SYMBOL(import_single_range); void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state) { if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i)) && - !iov_iter_is_kvec(i)) + !iov_iter_is_kvec(i) && !iter_is_ubuf(i)) return; i->iov_offset = state->iov_offset; i->count = state->count; + if (iter_is_ubuf(i)) + return; /* * For the *vec iters, nr_segs + iov is constant - if we increment * the vec, then we also decrement the nr_segs count. Hence we don't -- cgit v1.2.3