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-rw-r--r--lib/iov_iter.c1847
1 files changed, 1847 insertions, 0 deletions
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
new file mode 100644
index 000000000000..896760bad455
--- /dev/null
+++ b/lib/iov_iter.c
@@ -0,0 +1,1847 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/export.h>
+#include <linux/bvec.h>
+#include <linux/fault-inject-usercopy.h>
+#include <linux/uio.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/splice.h>
+#include <linux/compat.h>
+#include <linux/scatterlist.h>
+#include <linux/instrumented.h>
+#include <linux/iov_iter.h>
+
+static __always_inline
+size_t copy_to_user_iter(void __user *iter_to, size_t progress,
+ size_t len, void *from, void *priv2)
+{
+ if (should_fail_usercopy())
+ return len;
+ if (access_ok(iter_to, len)) {
+ from += progress;
+ instrument_copy_to_user(iter_to, from, len);
+ len = raw_copy_to_user(iter_to, from, len);
+ }
+ return len;
+}
+
+static __always_inline
+size_t copy_to_user_iter_nofault(void __user *iter_to, size_t progress,
+ size_t len, void *from, void *priv2)
+{
+ ssize_t res;
+
+ if (should_fail_usercopy())
+ return len;
+
+ from += progress;
+ res = copy_to_user_nofault(iter_to, from, len);
+ return res < 0 ? len : res;
+}
+
+static __always_inline
+size_t copy_from_user_iter(void __user *iter_from, size_t progress,
+ size_t len, void *to, void *priv2)
+{
+ size_t res = len;
+
+ if (should_fail_usercopy())
+ return len;
+ if (can_do_masked_user_access()) {
+ iter_from = mask_user_address(iter_from);
+ } else {
+ if (!access_ok(iter_from, len))
+ return res;
+
+ /*
+ * Ensure that bad access_ok() speculation will not
+ * lead to nasty side effects *after* the copy is
+ * finished:
+ */
+ barrier_nospec();
+ }
+ to += progress;
+ instrument_copy_from_user_before(to, iter_from, len);
+ res = raw_copy_from_user(to, iter_from, len);
+ instrument_copy_from_user_after(to, iter_from, len, res);
+
+ return res;
+}
+
+static __always_inline
+size_t memcpy_to_iter(void *iter_to, size_t progress,
+ size_t len, void *from, void *priv2)
+{
+ memcpy(iter_to, from + progress, len);
+ return 0;
+}
+
+static __always_inline
+size_t memcpy_from_iter(void *iter_from, size_t progress,
+ size_t len, void *to, void *priv2)
+{
+ memcpy(to + progress, iter_from, len);
+ return 0;
+}
+
+/*
+ * fault_in_iov_iter_readable - fault in iov iterator for reading
+ * @i: iterator
+ * @size: maximum length
+ *
+ * Fault in one or more iovecs of the given iov_iter, to a maximum length of
+ * @size. For each iovec, fault in each page that constitutes the iovec.
+ *
+ * Returns the number of bytes not faulted in (like copy_to_user() and
+ * copy_from_user()).
+ *
+ * Always returns 0 for non-userspace iterators.
+ */
+size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t size)
+{
+ 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;
+
+ size -= count;
+ for (p = iter_iov(i), skip = i->iov_offset; count; p++, skip = 0) {
+ size_t len = min(count, p->iov_len - skip);
+ size_t ret;
+
+ if (unlikely(!len))
+ continue;
+ ret = fault_in_readable(p->iov_base + skip, len);
+ count -= len - ret;
+ if (ret)
+ break;
+ }
+ return count + size;
+ }
+ return 0;
+}
+EXPORT_SYMBOL(fault_in_iov_iter_readable);
+
+/*
+ * fault_in_iov_iter_writeable - fault in iov iterator for writing
+ * @i: iterator
+ * @size: maximum length
+ *
+ * Faults in the iterator using get_user_pages(), i.e., without triggering
+ * hardware page faults. This is primarily useful when we already know that
+ * some or all of the pages in @i aren't in memory.
+ *
+ * Returns the number of bytes not faulted in, like copy_to_user() and
+ * copy_from_user().
+ *
+ * Always returns 0 for non-user-space iterators.
+ */
+size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t size)
+{
+ 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;
+
+ size -= count;
+ for (p = iter_iov(i), skip = i->iov_offset; count; p++, skip = 0) {
+ size_t len = min(count, p->iov_len - skip);
+ size_t ret;
+
+ if (unlikely(!len))
+ continue;
+ ret = fault_in_safe_writeable(p->iov_base + skip, len);
+ count -= len - ret;
+ if (ret)
+ break;
+ }
+ return count + size;
+ }
+ return 0;
+}
+EXPORT_SYMBOL(fault_in_iov_iter_writeable);
+
+void iov_iter_init(struct iov_iter *i, unsigned int direction,
+ const struct iovec *iov, unsigned long nr_segs,
+ size_t count)
+{
+ WARN_ON(direction & ~(READ | WRITE));
+ *i = (struct iov_iter) {
+ .iter_type = ITER_IOVEC,
+ .nofault = false,
+ .data_source = direction,
+ .__iov = iov,
+ .nr_segs = nr_segs,
+ .iov_offset = 0,
+ .count = count
+ };
+}
+EXPORT_SYMBOL(iov_iter_init);
+
+size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
+{
+ if (WARN_ON_ONCE(i->data_source))
+ return 0;
+ if (user_backed_iter(i))
+ might_fault();
+ return iterate_and_advance(i, bytes, (void *)addr,
+ copy_to_user_iter, memcpy_to_iter);
+}
+EXPORT_SYMBOL(_copy_to_iter);
+
+#ifdef CONFIG_ARCH_HAS_COPY_MC
+static __always_inline
+size_t copy_to_user_iter_mc(void __user *iter_to, size_t progress,
+ size_t len, void *from, void *priv2)
+{
+ if (access_ok(iter_to, len)) {
+ from += progress;
+ instrument_copy_to_user(iter_to, from, len);
+ len = copy_mc_to_user(iter_to, from, len);
+ }
+ return len;
+}
+
+static __always_inline
+size_t memcpy_to_iter_mc(void *iter_to, size_t progress,
+ size_t len, void *from, void *priv2)
+{
+ return copy_mc_to_kernel(iter_to, from + progress, len);
+}
+
+/**
+ * _copy_mc_to_iter - copy to iter with source memory error exception handling
+ * @addr: source kernel address
+ * @bytes: total transfer length
+ * @i: destination iterator
+ *
+ * The pmem driver deploys this for the dax operation
+ * (dax_copy_to_iter()) for dax reads (bypass page-cache and the
+ * block-layer). Upon #MC read(2) aborts and returns EIO or the bytes
+ * successfully copied.
+ *
+ * The main differences between this and typical _copy_to_iter().
+ *
+ * * Typical tail/residue handling after a fault retries the copy
+ * byte-by-byte until the fault happens again. Re-triggering machine
+ * checks is potentially fatal so the implementation uses source
+ * alignment and poison alignment assumptions to avoid re-triggering
+ * hardware exceptions.
+ *
+ * * ITER_KVEC and ITER_BVEC can return short copies. Compare to
+ * copy_to_iter() where only ITER_IOVEC attempts might return a short copy.
+ *
+ * Return: number of bytes copied (may be %0)
+ */
+size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
+{
+ if (WARN_ON_ONCE(i->data_source))
+ return 0;
+ if (user_backed_iter(i))
+ might_fault();
+ return iterate_and_advance(i, bytes, (void *)addr,
+ copy_to_user_iter_mc, memcpy_to_iter_mc);
+}
+EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
+#endif /* CONFIG_ARCH_HAS_COPY_MC */
+
+static __always_inline
+size_t __copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
+{
+ return iterate_and_advance(i, bytes, addr,
+ copy_from_user_iter, memcpy_from_iter);
+}
+
+size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
+{
+ if (WARN_ON_ONCE(!i->data_source))
+ return 0;
+
+ if (user_backed_iter(i))
+ might_fault();
+ return __copy_from_iter(addr, bytes, i);
+}
+EXPORT_SYMBOL(_copy_from_iter);
+
+static __always_inline
+size_t copy_from_user_iter_nocache(void __user *iter_from, size_t progress,
+ size_t len, void *to, void *priv2)
+{
+ return __copy_from_user_inatomic_nocache(to + progress, iter_from, len);
+}
+
+size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
+{
+ if (WARN_ON_ONCE(!i->data_source))
+ return 0;
+
+ return iterate_and_advance(i, bytes, addr,
+ copy_from_user_iter_nocache,
+ memcpy_from_iter);
+}
+EXPORT_SYMBOL(_copy_from_iter_nocache);
+
+#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
+static __always_inline
+size_t copy_from_user_iter_flushcache(void __user *iter_from, size_t progress,
+ size_t len, void *to, void *priv2)
+{
+ return __copy_from_user_flushcache(to + progress, iter_from, len);
+}
+
+static __always_inline
+size_t memcpy_from_iter_flushcache(void *iter_from, size_t progress,
+ size_t len, void *to, void *priv2)
+{
+ memcpy_flushcache(to + progress, iter_from, len);
+ return 0;
+}
+
+/**
+ * _copy_from_iter_flushcache - write destination through cpu cache
+ * @addr: destination kernel address
+ * @bytes: total transfer length
+ * @i: source iterator
+ *
+ * The pmem driver arranges for filesystem-dax to use this facility via
+ * dax_copy_from_iter() for ensuring that writes to persistent memory
+ * are flushed through the CPU cache. It is differentiated from
+ * _copy_from_iter_nocache() in that guarantees all data is flushed for
+ * all iterator types. The _copy_from_iter_nocache() only attempts to
+ * bypass the cache for the ITER_IOVEC case, and on some archs may use
+ * instructions that strand dirty-data in the cache.
+ *
+ * Return: number of bytes copied (may be %0)
+ */
+size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
+{
+ if (WARN_ON_ONCE(!i->data_source))
+ return 0;
+
+ return iterate_and_advance(i, bytes, addr,
+ copy_from_user_iter_flushcache,
+ memcpy_from_iter_flushcache);
+}
+EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
+#endif
+
+static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
+{
+ struct page *head;
+ size_t v = n + offset;
+
+ /*
+ * The general case needs to access the page order in order
+ * to compute the page size.
+ * However, we mostly deal with order-0 pages and thus can
+ * avoid a possible cache line miss for requests that fit all
+ * page orders.
+ */
+ if (n <= v && v <= PAGE_SIZE)
+ return true;
+
+ head = compound_head(page);
+ v += (page - head) << PAGE_SHIFT;
+
+ if (WARN_ON(n > v || v > page_size(head)))
+ return false;
+ return true;
+}
+
+size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ size_t res = 0;
+ if (!page_copy_sane(page, offset, bytes))
+ return 0;
+ if (WARN_ON_ONCE(i->data_source))
+ return 0;
+ page += offset / PAGE_SIZE; // first subpage
+ offset %= PAGE_SIZE;
+ while (1) {
+ void *kaddr = kmap_local_page(page);
+ size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
+ n = _copy_to_iter(kaddr + offset, n, i);
+ kunmap_local(kaddr);
+ res += n;
+ bytes -= n;
+ if (!bytes || !n)
+ break;
+ offset += n;
+ if (offset == PAGE_SIZE) {
+ page++;
+ offset = 0;
+ }
+ }
+ return res;
+}
+EXPORT_SYMBOL(copy_page_to_iter);
+
+size_t copy_page_to_iter_nofault(struct page *page, unsigned offset, size_t bytes,
+ struct iov_iter *i)
+{
+ size_t res = 0;
+
+ if (!page_copy_sane(page, offset, bytes))
+ return 0;
+ if (WARN_ON_ONCE(i->data_source))
+ return 0;
+ page += offset / PAGE_SIZE; // first subpage
+ offset %= PAGE_SIZE;
+ while (1) {
+ void *kaddr = kmap_local_page(page);
+ size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
+
+ n = iterate_and_advance(i, n, kaddr + offset,
+ copy_to_user_iter_nofault,
+ memcpy_to_iter);
+ kunmap_local(kaddr);
+ res += n;
+ bytes -= n;
+ if (!bytes || !n)
+ break;
+ offset += n;
+ if (offset == PAGE_SIZE) {
+ page++;
+ offset = 0;
+ }
+ }
+ return res;
+}
+EXPORT_SYMBOL(copy_page_to_iter_nofault);
+
+size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ size_t res = 0;
+ if (!page_copy_sane(page, offset, bytes))
+ return 0;
+ page += offset / PAGE_SIZE; // first subpage
+ offset %= PAGE_SIZE;
+ while (1) {
+ void *kaddr = kmap_local_page(page);
+ size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
+ n = _copy_from_iter(kaddr + offset, n, i);
+ kunmap_local(kaddr);
+ res += n;
+ bytes -= n;
+ if (!bytes || !n)
+ break;
+ offset += n;
+ if (offset == PAGE_SIZE) {
+ page++;
+ offset = 0;
+ }
+ }
+ return res;
+}
+EXPORT_SYMBOL(copy_page_from_iter);
+
+static __always_inline
+size_t zero_to_user_iter(void __user *iter_to, size_t progress,
+ size_t len, void *priv, void *priv2)
+{
+ return clear_user(iter_to, len);
+}
+
+static __always_inline
+size_t zero_to_iter(void *iter_to, size_t progress,
+ size_t len, void *priv, void *priv2)
+{
+ memset(iter_to, 0, len);
+ return 0;
+}
+
+size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
+{
+ return iterate_and_advance(i, bytes, NULL,
+ zero_to_user_iter, zero_to_iter);
+}
+EXPORT_SYMBOL(iov_iter_zero);
+
+size_t copy_folio_from_iter_atomic(struct folio *folio, size_t offset,
+ size_t bytes, struct iov_iter *i)
+{
+ size_t n, copied = 0;
+
+ if (!page_copy_sane(&folio->page, offset, bytes))
+ return 0;
+ if (WARN_ON_ONCE(!i->data_source))
+ return 0;
+
+ do {
+ char *to = kmap_local_folio(folio, offset);
+
+ n = bytes - copied;
+ if (folio_test_partial_kmap(folio) &&
+ n > PAGE_SIZE - offset_in_page(offset))
+ n = PAGE_SIZE - offset_in_page(offset);
+
+ pagefault_disable();
+ n = __copy_from_iter(to, n, i);
+ pagefault_enable();
+ kunmap_local(to);
+ copied += n;
+ offset += n;
+ } while (copied != bytes && n > 0);
+
+ return copied;
+}
+EXPORT_SYMBOL(copy_folio_from_iter_atomic);
+
+static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
+{
+ const struct bio_vec *bvec, *end;
+
+ if (!i->count)
+ return;
+ i->count -= size;
+
+ size += i->iov_offset;
+
+ for (bvec = i->bvec, end = bvec + i->nr_segs; bvec < end; bvec++) {
+ if (likely(size < bvec->bv_len))
+ break;
+ size -= bvec->bv_len;
+ }
+ i->iov_offset = size;
+ i->nr_segs -= bvec - i->bvec;
+ i->bvec = bvec;
+}
+
+static void iov_iter_iovec_advance(struct iov_iter *i, size_t size)
+{
+ const struct iovec *iov, *end;
+
+ if (!i->count)
+ return;
+ i->count -= size;
+
+ size += i->iov_offset; // from beginning of current segment
+ for (iov = iter_iov(i), end = iov + i->nr_segs; iov < end; iov++) {
+ if (likely(size < iov->iov_len))
+ break;
+ size -= iov->iov_len;
+ }
+ i->iov_offset = size;
+ i->nr_segs -= iov - iter_iov(i);
+ i->__iov = iov;
+}
+
+static void iov_iter_folioq_advance(struct iov_iter *i, size_t size)
+{
+ const struct folio_queue *folioq = i->folioq;
+ unsigned int slot = i->folioq_slot;
+
+ if (!i->count)
+ return;
+ i->count -= size;
+
+ if (slot >= folioq_nr_slots(folioq)) {
+ folioq = folioq->next;
+ slot = 0;
+ }
+
+ size += i->iov_offset; /* From beginning of current segment. */
+ do {
+ size_t fsize = folioq_folio_size(folioq, slot);
+
+ if (likely(size < fsize))
+ break;
+ size -= fsize;
+ slot++;
+ if (slot >= folioq_nr_slots(folioq) && folioq->next) {
+ folioq = folioq->next;
+ slot = 0;
+ }
+ } while (size);
+
+ i->iov_offset = size;
+ i->folioq_slot = slot;
+ i->folioq = folioq;
+}
+
+void iov_iter_advance(struct iov_iter *i, size_t size)
+{
+ if (unlikely(i->count < size))
+ size = i->count;
+ 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_folioq(i)) {
+ iov_iter_folioq_advance(i, size);
+ } else if (iov_iter_is_discard(i)) {
+ i->count -= size;
+ }
+}
+EXPORT_SYMBOL(iov_iter_advance);
+
+static void iov_iter_folioq_revert(struct iov_iter *i, size_t unroll)
+{
+ const struct folio_queue *folioq = i->folioq;
+ unsigned int slot = i->folioq_slot;
+
+ for (;;) {
+ size_t fsize;
+
+ if (slot == 0) {
+ folioq = folioq->prev;
+ slot = folioq_nr_slots(folioq);
+ }
+ slot--;
+
+ fsize = folioq_folio_size(folioq, slot);
+ if (unroll <= fsize) {
+ i->iov_offset = fsize - unroll;
+ break;
+ }
+ unroll -= fsize;
+ }
+
+ i->folioq_slot = slot;
+ i->folioq = folioq;
+}
+
+void iov_iter_revert(struct iov_iter *i, size_t unroll)
+{
+ if (!unroll)
+ return;
+ if (WARN_ON(unroll > MAX_RW_COUNT))
+ return;
+ i->count += unroll;
+ if (unlikely(iov_iter_is_discard(i)))
+ return;
+ if (unroll <= i->iov_offset) {
+ i->iov_offset -= unroll;
+ return;
+ }
+ unroll -= i->iov_offset;
+ 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.
+ */
+ } else if (iov_iter_is_bvec(i)) {
+ const struct bio_vec *bvec = i->bvec;
+ while (1) {
+ size_t n = (--bvec)->bv_len;
+ i->nr_segs++;
+ if (unroll <= n) {
+ i->bvec = bvec;
+ i->iov_offset = n - unroll;
+ return;
+ }
+ unroll -= n;
+ }
+ } else if (iov_iter_is_folioq(i)) {
+ i->iov_offset = 0;
+ iov_iter_folioq_revert(i, unroll);
+ } else { /* same logics for iovec and kvec */
+ const struct iovec *iov = iter_iov(i);
+ while (1) {
+ size_t n = (--iov)->iov_len;
+ i->nr_segs++;
+ if (unroll <= n) {
+ i->__iov = iov;
+ i->iov_offset = n - unroll;
+ return;
+ }
+ unroll -= n;
+ }
+ }
+}
+EXPORT_SYMBOL(iov_iter_revert);
+
+/*
+ * Return the count of just the current iov_iter segment.
+ */
+size_t iov_iter_single_seg_count(const struct iov_iter *i)
+{
+ if (i->nr_segs > 1) {
+ if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
+ return min(i->count, iter_iov(i)->iov_len - i->iov_offset);
+ if (iov_iter_is_bvec(i))
+ return min(i->count, i->bvec->bv_len - i->iov_offset);
+ }
+ if (unlikely(iov_iter_is_folioq(i)))
+ return !i->count ? 0 :
+ umin(folioq_folio_size(i->folioq, i->folioq_slot), i->count);
+ return i->count;
+}
+EXPORT_SYMBOL(iov_iter_single_seg_count);
+
+void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
+ const struct kvec *kvec, unsigned long nr_segs,
+ size_t count)
+{
+ WARN_ON(direction & ~(READ | WRITE));
+ *i = (struct iov_iter){
+ .iter_type = ITER_KVEC,
+ .data_source = direction,
+ .kvec = kvec,
+ .nr_segs = nr_segs,
+ .iov_offset = 0,
+ .count = count
+ };
+}
+EXPORT_SYMBOL(iov_iter_kvec);
+
+void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
+ const struct bio_vec *bvec, unsigned long nr_segs,
+ size_t count)
+{
+ WARN_ON(direction & ~(READ | WRITE));
+ *i = (struct iov_iter){
+ .iter_type = ITER_BVEC,
+ .data_source = direction,
+ .bvec = bvec,
+ .nr_segs = nr_segs,
+ .iov_offset = 0,
+ .count = count
+ };
+}
+EXPORT_SYMBOL(iov_iter_bvec);
+
+/**
+ * iov_iter_folio_queue - Initialise an I/O iterator to use the folios in a folio queue
+ * @i: The iterator to initialise.
+ * @direction: The direction of the transfer.
+ * @folioq: The starting point in the folio queue.
+ * @first_slot: The first slot in the folio queue to use
+ * @offset: The offset into the folio in the first slot to start at
+ * @count: The size of the I/O buffer in bytes.
+ *
+ * Set up an I/O iterator to either draw data out of the pages attached to an
+ * inode or to inject data into those pages. The pages *must* be prevented
+ * from evaporation, either by taking a ref on them or locking them by the
+ * caller.
+ */
+void iov_iter_folio_queue(struct iov_iter *i, unsigned int direction,
+ const struct folio_queue *folioq, unsigned int first_slot,
+ unsigned int offset, size_t count)
+{
+ BUG_ON(direction & ~1);
+ *i = (struct iov_iter) {
+ .iter_type = ITER_FOLIOQ,
+ .data_source = direction,
+ .folioq = folioq,
+ .folioq_slot = first_slot,
+ .count = count,
+ .iov_offset = offset,
+ };
+}
+EXPORT_SYMBOL(iov_iter_folio_queue);
+
+/**
+ * iov_iter_xarray - Initialise an I/O iterator to use the pages in an xarray
+ * @i: The iterator to initialise.
+ * @direction: The direction of the transfer.
+ * @xarray: The xarray to access.
+ * @start: The start file position.
+ * @count: The size of the I/O buffer in bytes.
+ *
+ * Set up an I/O iterator to either draw data out of the pages attached to an
+ * inode or to inject data into those pages. The pages *must* be prevented
+ * from evaporation, either by taking a ref on them or locking them by the
+ * caller.
+ */
+void iov_iter_xarray(struct iov_iter *i, unsigned int direction,
+ struct xarray *xarray, loff_t start, size_t count)
+{
+ BUG_ON(direction & ~1);
+ *i = (struct iov_iter) {
+ .iter_type = ITER_XARRAY,
+ .data_source = direction,
+ .xarray = xarray,
+ .xarray_start = start,
+ .count = count,
+ .iov_offset = 0
+ };
+}
+EXPORT_SYMBOL(iov_iter_xarray);
+
+/**
+ * iov_iter_discard - Initialise an I/O iterator that discards data
+ * @i: The iterator to initialise.
+ * @direction: The direction of the transfer.
+ * @count: The size of the I/O buffer in bytes.
+ *
+ * Set up an I/O iterator that just discards everything that's written to it.
+ * It's only available as a READ iterator.
+ */
+void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
+{
+ BUG_ON(direction != READ);
+ *i = (struct iov_iter){
+ .iter_type = ITER_DISCARD,
+ .data_source = false,
+ .count = count,
+ .iov_offset = 0
+ };
+}
+EXPORT_SYMBOL(iov_iter_discard);
+
+static unsigned long iov_iter_alignment_iovec(const struct iov_iter *i)
+{
+ const struct iovec *iov = iter_iov(i);
+ unsigned long res = 0;
+ size_t size = i->count;
+ size_t skip = i->iov_offset;
+
+ do {
+ size_t len = iov->iov_len - skip;
+ if (len) {
+ res |= (unsigned long)iov->iov_base + skip;
+ if (len > size)
+ len = size;
+ res |= len;
+ size -= len;
+ }
+ iov++;
+ skip = 0;
+ } while (size);
+ return res;
+}
+
+static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i)
+{
+ const struct bio_vec *bvec = i->bvec;
+ unsigned res = 0;
+ size_t size = i->count;
+ unsigned skip = i->iov_offset;
+
+ do {
+ size_t len = bvec->bv_len - skip;
+ res |= (unsigned long)bvec->bv_offset + skip;
+ if (len > size)
+ len = size;
+ res |= len;
+ bvec++;
+ size -= len;
+ skip = 0;
+ } while (size);
+
+ return res;
+}
+
+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);
+
+ if (iov_iter_is_bvec(i))
+ return iov_iter_alignment_bvec(i);
+
+ /* With both xarray and folioq types, we're dealing with whole folios. */
+ if (iov_iter_is_folioq(i))
+ return i->iov_offset | i->count;
+ if (iov_iter_is_xarray(i))
+ return (i->xarray_start + i->iov_offset) | i->count;
+
+ return 0;
+}
+EXPORT_SYMBOL(iov_iter_alignment);
+
+unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
+{
+ unsigned long res = 0;
+ unsigned long v = 0;
+ size_t size = i->count;
+ unsigned k;
+
+ if (iter_is_ubuf(i))
+ return 0;
+
+ if (WARN_ON(!iter_is_iovec(i)))
+ return ~0U;
+
+ for (k = 0; k < i->nr_segs; k++) {
+ const struct iovec *iov = iter_iov(i) + k;
+ if (iov->iov_len) {
+ unsigned long base = (unsigned long)iov->iov_base;
+ if (v) // if not the first one
+ res |= base | v; // this start | previous end
+ v = base + iov->iov_len;
+ if (size <= iov->iov_len)
+ break;
+ size -= iov->iov_len;
+ }
+ }
+ return res;
+}
+EXPORT_SYMBOL(iov_iter_gap_alignment);
+
+static int want_pages_array(struct page ***res, size_t size,
+ size_t start, unsigned int maxpages)
+{
+ unsigned int count = DIV_ROUND_UP(size + start, PAGE_SIZE);
+
+ if (count > maxpages)
+ count = maxpages;
+ WARN_ON(!count); // caller should've prevented that
+ if (!*res) {
+ *res = kvmalloc_array(count, sizeof(struct page *), GFP_KERNEL);
+ if (!*res)
+ return 0;
+ }
+ return count;
+}
+
+static ssize_t iter_folioq_get_pages(struct iov_iter *iter,
+ struct page ***ppages, size_t maxsize,
+ unsigned maxpages, size_t *_start_offset)
+{
+ const struct folio_queue *folioq = iter->folioq;
+ struct page **pages;
+ unsigned int slot = iter->folioq_slot;
+ size_t extracted = 0, count = iter->count, iov_offset = iter->iov_offset;
+
+ if (slot >= folioq_nr_slots(folioq)) {
+ folioq = folioq->next;
+ slot = 0;
+ if (WARN_ON(iov_offset != 0))
+ return -EIO;
+ }
+
+ maxpages = want_pages_array(ppages, maxsize, iov_offset & ~PAGE_MASK, maxpages);
+ if (!maxpages)
+ return -ENOMEM;
+ *_start_offset = iov_offset & ~PAGE_MASK;
+ pages = *ppages;
+
+ for (;;) {
+ struct folio *folio = folioq_folio(folioq, slot);
+ size_t offset = iov_offset, fsize = folioq_folio_size(folioq, slot);
+ size_t part = PAGE_SIZE - offset % PAGE_SIZE;
+
+ if (offset < fsize) {
+ part = umin(part, umin(maxsize - extracted, fsize - offset));
+ count -= part;
+ iov_offset += part;
+ extracted += part;
+
+ *pages = folio_page(folio, offset / PAGE_SIZE);
+ get_page(*pages);
+ pages++;
+ maxpages--;
+ }
+
+ if (maxpages == 0 || extracted >= maxsize)
+ break;
+
+ if (iov_offset >= fsize) {
+ iov_offset = 0;
+ slot++;
+ if (slot == folioq_nr_slots(folioq) && folioq->next) {
+ folioq = folioq->next;
+ slot = 0;
+ }
+ }
+ }
+
+ iter->count = count;
+ iter->iov_offset = iov_offset;
+ iter->folioq = folioq;
+ iter->folioq_slot = slot;
+ return extracted;
+}
+
+static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa,
+ pgoff_t index, unsigned int nr_pages)
+{
+ XA_STATE(xas, xa, index);
+ struct folio *folio;
+ unsigned int ret = 0;
+
+ rcu_read_lock();
+ for (folio = xas_load(&xas); folio; folio = xas_next(&xas)) {
+ if (xas_retry(&xas, folio))
+ continue;
+
+ /* Has the folio moved or been split? */
+ if (unlikely(folio != xas_reload(&xas))) {
+ xas_reset(&xas);
+ continue;
+ }
+
+ pages[ret] = folio_file_page(folio, xas.xa_index);
+ folio_get(folio);
+ if (++ret == nr_pages)
+ break;
+ }
+ rcu_read_unlock();
+ return ret;
+}
+
+static ssize_t iter_xarray_get_pages(struct iov_iter *i,
+ struct page ***pages, size_t maxsize,
+ unsigned maxpages, size_t *_start_offset)
+{
+ unsigned nr, offset, count;
+ pgoff_t index;
+ loff_t pos;
+
+ pos = i->xarray_start + i->iov_offset;
+ index = pos >> PAGE_SHIFT;
+ offset = pos & ~PAGE_MASK;
+ *_start_offset = offset;
+
+ count = want_pages_array(pages, maxsize, offset, maxpages);
+ if (!count)
+ return -ENOMEM;
+ nr = iter_xarray_populate_pages(*pages, i->xarray, index, count);
+ if (nr == 0)
+ return 0;
+
+ maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
+ i->iov_offset += maxsize;
+ i->count -= maxsize;
+ return maxsize;
+}
+
+/* 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) {
+ const struct iovec *iov = iter_iov(i) + k;
+ size_t len = iov->iov_len - skip;
+
+ if (unlikely(!len))
+ continue;
+ if (*size > len)
+ *size = len;
+ return (unsigned long)iov->iov_base + skip;
+ }
+ BUG(); // if it had been empty, we wouldn't get called
+}
+
+/* must be done on non-empty ITER_BVEC one */
+static struct page *first_bvec_segment(const struct iov_iter *i,
+ size_t *size, size_t *start)
+{
+ struct page *page;
+ size_t skip = i->iov_offset, len;
+
+ len = i->bvec->bv_len - skip;
+ if (*size > len)
+ *size = len;
+ skip += i->bvec->bv_offset;
+ page = i->bvec->bv_page + skip / PAGE_SIZE;
+ *start = skip % PAGE_SIZE;
+ return page;
+}
+
+static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
+ struct page ***pages, size_t maxsize,
+ unsigned int maxpages, size_t *start)
+{
+ unsigned int n, gup_flags = 0;
+
+ if (maxsize > i->count)
+ maxsize = i->count;
+ if (!maxsize)
+ return 0;
+ if (maxsize > MAX_RW_COUNT)
+ maxsize = MAX_RW_COUNT;
+
+ if (likely(user_backed_iter(i))) {
+ unsigned long addr;
+ int res;
+
+ if (iov_iter_rw(i) != WRITE)
+ gup_flags |= FOLL_WRITE;
+ if (i->nofault)
+ gup_flags |= FOLL_NOFAULT;
+
+ addr = first_iovec_segment(i, &maxsize);
+ *start = addr % PAGE_SIZE;
+ addr &= PAGE_MASK;
+ n = want_pages_array(pages, maxsize, *start, maxpages);
+ if (!n)
+ return -ENOMEM;
+ res = get_user_pages_fast(addr, n, gup_flags, *pages);
+ if (unlikely(res <= 0))
+ return res;
+ maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - *start);
+ iov_iter_advance(i, maxsize);
+ return maxsize;
+ }
+ if (iov_iter_is_bvec(i)) {
+ struct page **p;
+ struct page *page;
+
+ page = first_bvec_segment(i, &maxsize, start);
+ n = want_pages_array(pages, maxsize, *start, maxpages);
+ if (!n)
+ return -ENOMEM;
+ p = *pages;
+ for (int k = 0; k < n; k++) {
+ struct folio *folio = page_folio(page + k);
+ p[k] = page + k;
+ if (!folio_test_slab(folio))
+ folio_get(folio);
+ }
+ maxsize = min_t(size_t, maxsize, n * PAGE_SIZE - *start);
+ i->count -= maxsize;
+ i->iov_offset += maxsize;
+ if (i->iov_offset == i->bvec->bv_len) {
+ i->iov_offset = 0;
+ i->bvec++;
+ i->nr_segs--;
+ }
+ return maxsize;
+ }
+ if (iov_iter_is_folioq(i))
+ return iter_folioq_get_pages(i, pages, maxsize, maxpages, start);
+ if (iov_iter_is_xarray(i))
+ return iter_xarray_get_pages(i, pages, maxsize, maxpages, start);
+ return -EFAULT;
+}
+
+ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
+ size_t maxsize, unsigned maxpages, size_t *start)
+{
+ if (!maxpages)
+ return 0;
+ BUG_ON(!pages);
+
+ return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, start);
+}
+EXPORT_SYMBOL(iov_iter_get_pages2);
+
+ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
+ struct page ***pages, size_t maxsize, size_t *start)
+{
+ ssize_t len;
+
+ *pages = NULL;
+
+ len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start);
+ if (len <= 0) {
+ kvfree(*pages);
+ *pages = NULL;
+ }
+ return len;
+}
+EXPORT_SYMBOL(iov_iter_get_pages_alloc2);
+
+static int iov_npages(const struct iov_iter *i, int maxpages)
+{
+ size_t skip = i->iov_offset, size = i->count;
+ const struct iovec *p;
+ int npages = 0;
+
+ for (p = iter_iov(i); size; skip = 0, p++) {
+ unsigned offs = offset_in_page(p->iov_base + skip);
+ size_t len = min(p->iov_len - skip, size);
+
+ if (len) {
+ size -= len;
+ npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
+ if (unlikely(npages > maxpages))
+ return maxpages;
+ }
+ }
+ return npages;
+}
+
+static int bvec_npages(const struct iov_iter *i, int maxpages)
+{
+ size_t skip = i->iov_offset, size = i->count;
+ const struct bio_vec *p;
+ int npages = 0;
+
+ for (p = i->bvec; size; skip = 0, p++) {
+ unsigned offs = (p->bv_offset + skip) % PAGE_SIZE;
+ size_t len = min(p->bv_len - skip, size);
+
+ size -= len;
+ npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
+ if (unlikely(npages > maxpages))
+ return maxpages;
+ }
+ return npages;
+}
+
+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);
+ if (iov_iter_is_bvec(i))
+ return bvec_npages(i, maxpages);
+ if (iov_iter_is_folioq(i)) {
+ unsigned offset = i->iov_offset % PAGE_SIZE;
+ int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE);
+ return min(npages, maxpages);
+ }
+ if (iov_iter_is_xarray(i)) {
+ unsigned offset = (i->xarray_start + i->iov_offset) % PAGE_SIZE;
+ int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE);
+ return min(npages, maxpages);
+ }
+ return 0;
+}
+EXPORT_SYMBOL(iov_iter_npages);
+
+const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
+{
+ *new = *old;
+ if (iov_iter_is_bvec(new))
+ return new->bvec = kmemdup(new->bvec,
+ new->nr_segs * sizeof(struct bio_vec),
+ flags);
+ 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);
+
+static __noclone int copy_compat_iovec_from_user(struct iovec *iov,
+ const struct iovec __user *uvec, u32 nr_segs)
+{
+ const struct compat_iovec __user *uiov =
+ (const struct compat_iovec __user *)uvec;
+ int ret = -EFAULT;
+ u32 i;
+
+ if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
+ return -EFAULT;
+
+ for (i = 0; i < nr_segs; i++) {
+ compat_uptr_t buf;
+ compat_ssize_t len;
+
+ unsafe_get_user(len, &uiov[i].iov_len, uaccess_end);
+ unsafe_get_user(buf, &uiov[i].iov_base, uaccess_end);
+
+ /* check for compat_size_t not fitting in compat_ssize_t .. */
+ if (len < 0) {
+ ret = -EINVAL;
+ goto uaccess_end;
+ }
+ iov[i].iov_base = compat_ptr(buf);
+ iov[i].iov_len = len;
+ }
+
+ ret = 0;
+uaccess_end:
+ user_access_end();
+ return ret;
+}
+
+static __noclone int copy_iovec_from_user(struct iovec *iov,
+ const struct iovec __user *uiov, unsigned long nr_segs)
+{
+ int ret = -EFAULT;
+
+ if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
+ return -EFAULT;
+
+ do {
+ void __user *buf;
+ ssize_t len;
+
+ unsafe_get_user(len, &uiov->iov_len, uaccess_end);
+ unsafe_get_user(buf, &uiov->iov_base, uaccess_end);
+
+ /* check for size_t not fitting in ssize_t .. */
+ if (unlikely(len < 0)) {
+ ret = -EINVAL;
+ goto uaccess_end;
+ }
+ iov->iov_base = buf;
+ iov->iov_len = len;
+
+ uiov++; iov++;
+ } while (--nr_segs);
+
+ ret = 0;
+uaccess_end:
+ user_access_end();
+ return ret;
+}
+
+struct iovec *iovec_from_user(const struct iovec __user *uvec,
+ unsigned long nr_segs, unsigned long fast_segs,
+ struct iovec *fast_iov, bool compat)
+{
+ struct iovec *iov = fast_iov;
+ int ret;
+
+ /*
+ * SuS says "The readv() function *may* fail if the iovcnt argument was
+ * less than or equal to 0, or greater than {IOV_MAX}. Linux has
+ * traditionally returned zero for zero segments, so...
+ */
+ if (nr_segs == 0)
+ return iov;
+ if (nr_segs > UIO_MAXIOV)
+ return ERR_PTR(-EINVAL);
+ if (nr_segs > fast_segs) {
+ iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
+ if (!iov)
+ return ERR_PTR(-ENOMEM);
+ }
+
+ if (unlikely(compat))
+ ret = copy_compat_iovec_from_user(iov, uvec, nr_segs);
+ else
+ ret = copy_iovec_from_user(iov, uvec, nr_segs);
+ if (ret) {
+ if (iov != fast_iov)
+ kfree(iov);
+ return ERR_PTR(ret);
+ }
+
+ return iov;
+}
+
+/*
+ * Single segment iovec supplied by the user, import it as ITER_UBUF.
+ */
+static ssize_t __import_iovec_ubuf(int type, const struct iovec __user *uvec,
+ struct iovec **iovp, struct iov_iter *i,
+ bool compat)
+{
+ struct iovec *iov = *iovp;
+ ssize_t ret;
+
+ *iovp = NULL;
+
+ if (compat)
+ ret = copy_compat_iovec_from_user(iov, uvec, 1);
+ else
+ ret = copy_iovec_from_user(iov, uvec, 1);
+ if (unlikely(ret))
+ return ret;
+
+ ret = import_ubuf(type, iov->iov_base, iov->iov_len, i);
+ if (unlikely(ret))
+ return ret;
+ return i->count;
+}
+
+ssize_t __import_iovec(int type, const struct iovec __user *uvec,
+ unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
+ struct iov_iter *i, bool compat)
+{
+ ssize_t total_len = 0;
+ unsigned long seg;
+ struct iovec *iov;
+
+ if (nr_segs == 1)
+ return __import_iovec_ubuf(type, uvec, iovp, i, compat);
+
+ iov = iovec_from_user(uvec, nr_segs, fast_segs, *iovp, compat);
+ if (IS_ERR(iov)) {
+ *iovp = NULL;
+ return PTR_ERR(iov);
+ }
+
+ /*
+ * According to the Single Unix Specification we should return EINVAL if
+ * an element length is < 0 when cast to ssize_t or if the total length
+ * would overflow the ssize_t return value of the system call.
+ *
+ * Linux caps all read/write calls to MAX_RW_COUNT, and avoids the
+ * overflow case.
+ */
+ for (seg = 0; seg < nr_segs; seg++) {
+ ssize_t len = (ssize_t)iov[seg].iov_len;
+
+ if (!access_ok(iov[seg].iov_base, len)) {
+ if (iov != *iovp)
+ kfree(iov);
+ *iovp = NULL;
+ return -EFAULT;
+ }
+
+ if (len > MAX_RW_COUNT - total_len) {
+ len = MAX_RW_COUNT - total_len;
+ iov[seg].iov_len = len;
+ }
+ total_len += len;
+ }
+
+ iov_iter_init(i, type, iov, nr_segs, total_len);
+ if (iov == *iovp)
+ *iovp = NULL;
+ else
+ *iovp = iov;
+ return total_len;
+}
+
+/**
+ * import_iovec() - Copy an array of &struct iovec from userspace
+ * into the kernel, check that it is valid, and initialize a new
+ * &struct iov_iter iterator to access it.
+ *
+ * @type: One of %READ or %WRITE.
+ * @uvec: Pointer to the userspace array.
+ * @nr_segs: Number of elements in userspace array.
+ * @fast_segs: Number of elements in @iov.
+ * @iovp: (input and output parameter) Pointer to pointer to (usually small
+ * on-stack) kernel array.
+ * @i: Pointer to iterator that will be initialized on success.
+ *
+ * If the array pointed to by *@iov is large enough to hold all @nr_segs,
+ * then this function places %NULL in *@iov on return. Otherwise, a new
+ * array will be allocated and the result placed in *@iov. This means that
+ * the caller may call kfree() on *@iov regardless of whether the small
+ * on-stack array was used or not (and regardless of whether this function
+ * returns an error or not).
+ *
+ * Return: Negative error code on error, bytes imported on success
+ */
+ssize_t import_iovec(int type, const struct iovec __user *uvec,
+ unsigned nr_segs, unsigned fast_segs,
+ struct iovec **iovp, struct iov_iter *i)
+{
+ return __import_iovec(type, uvec, nr_segs, fast_segs, iovp, i,
+ in_compat_syscall());
+}
+EXPORT_SYMBOL(import_iovec);
+
+int import_ubuf(int rw, void __user *buf, size_t len, struct iov_iter *i)
+{
+ if (len > MAX_RW_COUNT)
+ len = MAX_RW_COUNT;
+ if (unlikely(!access_ok(buf, len)))
+ return -EFAULT;
+
+ iov_iter_ubuf(i, rw, buf, len);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(import_ubuf);
+
+/**
+ * iov_iter_restore() - Restore a &struct iov_iter to the same state as when
+ * iov_iter_save_state() was called.
+ *
+ * @i: &struct iov_iter to restore
+ * @state: state to restore from
+ *
+ * Used after iov_iter_save_state() to bring restore @i, if operations may
+ * have advanced it.
+ *
+ * Note: only works on ITER_IOVEC, ITER_BVEC, and ITER_KVEC
+ */
+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) &&
+ !iter_is_ubuf(i)) && !iov_iter_is_kvec(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
+ * need to track both of these, just one is enough and we can deduct
+ * the other from that. ITER_KVEC and ITER_IOVEC are the same struct
+ * size, so we can just increment the iov pointer as they are unionzed.
+ * ITER_BVEC _may_ be the same size on some archs, but on others it is
+ * not. Be safe and handle it separately.
+ */
+ BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
+ if (iov_iter_is_bvec(i))
+ i->bvec -= state->nr_segs - i->nr_segs;
+ else
+ i->__iov -= state->nr_segs - i->nr_segs;
+ i->nr_segs = state->nr_segs;
+}
+
+/*
+ * Extract a list of contiguous pages from an ITER_FOLIOQ iterator. This does
+ * not get references on the pages, nor does it get a pin on them.
+ */
+static ssize_t iov_iter_extract_folioq_pages(struct iov_iter *i,
+ struct page ***pages, size_t maxsize,
+ unsigned int maxpages,
+ iov_iter_extraction_t extraction_flags,
+ size_t *offset0)
+{
+ const struct folio_queue *folioq = i->folioq;
+ struct page **p;
+ unsigned int nr = 0;
+ size_t extracted = 0, offset, slot = i->folioq_slot;
+
+ if (slot >= folioq_nr_slots(folioq)) {
+ folioq = folioq->next;
+ slot = 0;
+ if (WARN_ON(i->iov_offset != 0))
+ return -EIO;
+ }
+
+ offset = i->iov_offset & ~PAGE_MASK;
+ *offset0 = offset;
+
+ maxpages = want_pages_array(pages, maxsize, offset, maxpages);
+ if (!maxpages)
+ return -ENOMEM;
+ p = *pages;
+
+ for (;;) {
+ struct folio *folio = folioq_folio(folioq, slot);
+ size_t offset = i->iov_offset, fsize = folioq_folio_size(folioq, slot);
+ size_t part = PAGE_SIZE - offset % PAGE_SIZE;
+
+ if (offset < fsize) {
+ part = umin(part, umin(maxsize - extracted, fsize - offset));
+ i->count -= part;
+ i->iov_offset += part;
+ extracted += part;
+
+ p[nr++] = folio_page(folio, offset / PAGE_SIZE);
+ }
+
+ if (nr >= maxpages || extracted >= maxsize)
+ break;
+
+ if (i->iov_offset >= fsize) {
+ i->iov_offset = 0;
+ slot++;
+ if (slot == folioq_nr_slots(folioq) && folioq->next) {
+ folioq = folioq->next;
+ slot = 0;
+ }
+ }
+ }
+
+ i->folioq = folioq;
+ i->folioq_slot = slot;
+ return extracted;
+}
+
+/*
+ * Extract a list of contiguous pages from an ITER_XARRAY iterator. This does not
+ * get references on the pages, nor does it get a pin on them.
+ */
+static ssize_t iov_iter_extract_xarray_pages(struct iov_iter *i,
+ struct page ***pages, size_t maxsize,
+ unsigned int maxpages,
+ iov_iter_extraction_t extraction_flags,
+ size_t *offset0)
+{
+ struct page **p;
+ struct folio *folio;
+ unsigned int nr = 0, offset;
+ loff_t pos = i->xarray_start + i->iov_offset;
+ XA_STATE(xas, i->xarray, pos >> PAGE_SHIFT);
+
+ offset = pos & ~PAGE_MASK;
+ *offset0 = offset;
+
+ maxpages = want_pages_array(pages, maxsize, offset, maxpages);
+ if (!maxpages)
+ return -ENOMEM;
+ p = *pages;
+
+ rcu_read_lock();
+ for (folio = xas_load(&xas); folio; folio = xas_next(&xas)) {
+ if (xas_retry(&xas, folio))
+ continue;
+
+ /* Has the folio moved or been split? */
+ if (unlikely(folio != xas_reload(&xas))) {
+ xas_reset(&xas);
+ continue;
+ }
+
+ p[nr++] = folio_file_page(folio, xas.xa_index);
+ if (nr == maxpages)
+ break;
+ }
+ rcu_read_unlock();
+
+ maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
+ iov_iter_advance(i, maxsize);
+ return maxsize;
+}
+
+/*
+ * Extract a list of virtually contiguous pages from an ITER_BVEC iterator.
+ * This does not get references on the pages, nor does it get a pin on them.
+ */
+static ssize_t iov_iter_extract_bvec_pages(struct iov_iter *i,
+ struct page ***pages, size_t maxsize,
+ unsigned int maxpages,
+ iov_iter_extraction_t extraction_flags,
+ size_t *offset0)
+{
+ size_t skip = i->iov_offset, size = 0;
+ struct bvec_iter bi;
+ int k = 0;
+
+ if (i->nr_segs == 0)
+ return 0;
+
+ if (i->iov_offset == i->bvec->bv_len) {
+ i->iov_offset = 0;
+ i->nr_segs--;
+ i->bvec++;
+ skip = 0;
+ }
+ bi.bi_idx = 0;
+ bi.bi_size = maxsize;
+ bi.bi_bvec_done = skip;
+
+ maxpages = want_pages_array(pages, maxsize, skip, maxpages);
+
+ while (bi.bi_size && bi.bi_idx < i->nr_segs) {
+ struct bio_vec bv = bvec_iter_bvec(i->bvec, bi);
+
+ /*
+ * The iov_iter_extract_pages interface only allows an offset
+ * into the first page. Break out of the loop if we see an
+ * offset into subsequent pages, the caller will have to call
+ * iov_iter_extract_pages again for the reminder.
+ */
+ if (k) {
+ if (bv.bv_offset)
+ break;
+ } else {
+ *offset0 = bv.bv_offset;
+ }
+
+ (*pages)[k++] = bv.bv_page;
+ size += bv.bv_len;
+
+ if (k >= maxpages)
+ break;
+
+ /*
+ * We are done when the end of the bvec doesn't align to a page
+ * boundary as that would create a hole in the returned space.
+ * The caller will handle this with another call to
+ * iov_iter_extract_pages.
+ */
+ if (bv.bv_offset + bv.bv_len != PAGE_SIZE)
+ break;
+
+ bvec_iter_advance_single(i->bvec, &bi, bv.bv_len);
+ }
+
+ iov_iter_advance(i, size);
+ return size;
+}
+
+/*
+ * Extract a list of virtually contiguous pages from an ITER_KVEC iterator.
+ * This does not get references on the pages, nor does it get a pin on them.
+ */
+static ssize_t iov_iter_extract_kvec_pages(struct iov_iter *i,
+ struct page ***pages, size_t maxsize,
+ unsigned int maxpages,
+ iov_iter_extraction_t extraction_flags,
+ size_t *offset0)
+{
+ struct page **p, *page;
+ const void *kaddr;
+ size_t skip = i->iov_offset, offset, len, size;
+ int k;
+
+ for (;;) {
+ if (i->nr_segs == 0)
+ return 0;
+ size = min(maxsize, i->kvec->iov_len - skip);
+ if (size)
+ break;
+ i->iov_offset = 0;
+ i->nr_segs--;
+ i->kvec++;
+ skip = 0;
+ }
+
+ kaddr = i->kvec->iov_base + skip;
+ offset = (unsigned long)kaddr & ~PAGE_MASK;
+ *offset0 = offset;
+
+ maxpages = want_pages_array(pages, size, offset, maxpages);
+ if (!maxpages)
+ return -ENOMEM;
+ p = *pages;
+
+ kaddr -= offset;
+ len = offset + size;
+ for (k = 0; k < maxpages; k++) {
+ size_t seg = min_t(size_t, len, PAGE_SIZE);
+
+ if (is_vmalloc_or_module_addr(kaddr))
+ page = vmalloc_to_page(kaddr);
+ else
+ page = virt_to_page(kaddr);
+
+ p[k] = page;
+ len -= seg;
+ kaddr += PAGE_SIZE;
+ }
+
+ size = min_t(size_t, size, maxpages * PAGE_SIZE - offset);
+ iov_iter_advance(i, size);
+ return size;
+}
+
+/*
+ * Extract a list of contiguous pages from a user iterator and get a pin on
+ * each of them. This should only be used if the iterator is user-backed
+ * (IOBUF/UBUF).
+ *
+ * It does not get refs on the pages, but the pages must be unpinned by the
+ * caller once the transfer is complete.
+ *
+ * This is safe to be used where background IO/DMA *is* going to be modifying
+ * the buffer; using a pin rather than a ref makes forces fork() to give the
+ * child a copy of the page.
+ */
+static ssize_t iov_iter_extract_user_pages(struct iov_iter *i,
+ struct page ***pages,
+ size_t maxsize,
+ unsigned int maxpages,
+ iov_iter_extraction_t extraction_flags,
+ size_t *offset0)
+{
+ unsigned long addr;
+ unsigned int gup_flags = 0;
+ size_t offset;
+ int res;
+
+ if (i->data_source == ITER_DEST)
+ gup_flags |= FOLL_WRITE;
+ if (extraction_flags & ITER_ALLOW_P2PDMA)
+ gup_flags |= FOLL_PCI_P2PDMA;
+ if (i->nofault)
+ gup_flags |= FOLL_NOFAULT;
+
+ addr = first_iovec_segment(i, &maxsize);
+ *offset0 = offset = addr % PAGE_SIZE;
+ addr &= PAGE_MASK;
+ maxpages = want_pages_array(pages, maxsize, offset, maxpages);
+ if (!maxpages)
+ return -ENOMEM;
+ res = pin_user_pages_fast(addr, maxpages, gup_flags, *pages);
+ if (unlikely(res <= 0))
+ return res;
+ maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - offset);
+ iov_iter_advance(i, maxsize);
+ return maxsize;
+}
+
+/**
+ * iov_iter_extract_pages - Extract a list of contiguous pages from an iterator
+ * @i: The iterator to extract from
+ * @pages: Where to return the list of pages
+ * @maxsize: The maximum amount of iterator to extract
+ * @maxpages: The maximum size of the list of pages
+ * @extraction_flags: Flags to qualify request
+ * @offset0: Where to return the starting offset into (*@pages)[0]
+ *
+ * Extract a list of contiguous pages from the current point of the iterator,
+ * advancing the iterator. The maximum number of pages and the maximum amount
+ * of page contents can be set.
+ *
+ * If *@pages is NULL, a page list will be allocated to the required size and
+ * *@pages will be set to its base. If *@pages is not NULL, it will be assumed
+ * that the caller allocated a page list at least @maxpages in size and this
+ * will be filled in.
+ *
+ * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA
+ * be allowed on the pages extracted.
+ *
+ * The iov_iter_extract_will_pin() function can be used to query how cleanup
+ * should be performed.
+ *
+ * Extra refs or pins on the pages may be obtained as follows:
+ *
+ * (*) If the iterator is user-backed (ITER_IOVEC/ITER_UBUF), pins will be
+ * added to the pages, but refs will not be taken.
+ * iov_iter_extract_will_pin() will return true.
+ *
+ * (*) If the iterator is ITER_KVEC, ITER_BVEC, ITER_FOLIOQ or ITER_XARRAY, the
+ * pages are merely listed; no extra refs or pins are obtained.
+ * iov_iter_extract_will_pin() will return 0.
+ *
+ * Note also:
+ *
+ * (*) Use with ITER_DISCARD is not supported as that has no content.
+ *
+ * On success, the function sets *@pages to the new pagelist, if allocated, and
+ * sets *offset0 to the offset into the first page.
+ *
+ * It may also return -ENOMEM and -EFAULT.
+ */
+ssize_t iov_iter_extract_pages(struct iov_iter *i,
+ struct page ***pages,
+ size_t maxsize,
+ unsigned int maxpages,
+ iov_iter_extraction_t extraction_flags,
+ size_t *offset0)
+{
+ maxsize = min_t(size_t, min_t(size_t, maxsize, i->count), MAX_RW_COUNT);
+ if (!maxsize)
+ return 0;
+
+ if (likely(user_backed_iter(i)))
+ return iov_iter_extract_user_pages(i, pages, maxsize,
+ maxpages, extraction_flags,
+ offset0);
+ if (iov_iter_is_kvec(i))
+ return iov_iter_extract_kvec_pages(i, pages, maxsize,
+ maxpages, extraction_flags,
+ offset0);
+ if (iov_iter_is_bvec(i))
+ return iov_iter_extract_bvec_pages(i, pages, maxsize,
+ maxpages, extraction_flags,
+ offset0);
+ if (iov_iter_is_folioq(i))
+ return iov_iter_extract_folioq_pages(i, pages, maxsize,
+ maxpages, extraction_flags,
+ offset0);
+ if (iov_iter_is_xarray(i))
+ return iov_iter_extract_xarray_pages(i, pages, maxsize,
+ maxpages, extraction_flags,
+ offset0);
+ return -EFAULT;
+}
+EXPORT_SYMBOL_GPL(iov_iter_extract_pages);
generated by cgit (git 2.34.1) at 2025-12-21 21:16:13 +0000