mirror of https://gitee.com/openkylin/linux.git
225 lines
5.3 KiB
C
225 lines
5.3 KiB
C
#include <linux/export.h>
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#include <linux/uio.h>
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#include <linux/pagemap.h>
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size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
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struct iov_iter *i)
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{
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size_t skip, copy, left, wanted;
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const struct iovec *iov;
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char __user *buf;
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void *kaddr, *from;
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if (unlikely(bytes > i->count))
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bytes = i->count;
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if (unlikely(!bytes))
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return 0;
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wanted = bytes;
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iov = i->iov;
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skip = i->iov_offset;
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buf = iov->iov_base + skip;
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copy = min(bytes, iov->iov_len - skip);
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if (!fault_in_pages_writeable(buf, copy)) {
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kaddr = kmap_atomic(page);
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from = kaddr + offset;
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/* first chunk, usually the only one */
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left = __copy_to_user_inatomic(buf, from, copy);
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copy -= left;
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skip += copy;
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from += copy;
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bytes -= copy;
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while (unlikely(!left && bytes)) {
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iov++;
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buf = iov->iov_base;
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copy = min(bytes, iov->iov_len);
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left = __copy_to_user_inatomic(buf, from, copy);
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copy -= left;
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skip = copy;
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from += copy;
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bytes -= copy;
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}
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if (likely(!bytes)) {
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kunmap_atomic(kaddr);
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goto done;
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}
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offset = from - kaddr;
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buf += copy;
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kunmap_atomic(kaddr);
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copy = min(bytes, iov->iov_len - skip);
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}
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/* Too bad - revert to non-atomic kmap */
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kaddr = kmap(page);
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from = kaddr + offset;
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left = __copy_to_user(buf, from, copy);
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copy -= left;
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skip += copy;
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from += copy;
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bytes -= copy;
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while (unlikely(!left && bytes)) {
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iov++;
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buf = iov->iov_base;
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copy = min(bytes, iov->iov_len);
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left = __copy_to_user(buf, from, copy);
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copy -= left;
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skip = copy;
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from += copy;
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bytes -= copy;
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}
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kunmap(page);
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done:
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i->count -= wanted - bytes;
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i->nr_segs -= iov - i->iov;
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i->iov = iov;
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i->iov_offset = skip;
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return wanted - bytes;
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}
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EXPORT_SYMBOL(copy_page_to_iter);
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static size_t __iovec_copy_from_user_inatomic(char *vaddr,
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const struct iovec *iov, size_t base, size_t bytes)
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{
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size_t copied = 0, left = 0;
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while (bytes) {
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char __user *buf = iov->iov_base + base;
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int copy = min(bytes, iov->iov_len - base);
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base = 0;
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left = __copy_from_user_inatomic(vaddr, buf, copy);
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copied += copy;
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bytes -= copy;
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vaddr += copy;
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iov++;
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if (unlikely(left))
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break;
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}
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return copied - left;
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}
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/*
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* Copy as much as we can into the page and return the number of bytes which
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* were successfully copied. If a fault is encountered then return the number of
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* bytes which were copied.
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*/
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size_t iov_iter_copy_from_user_atomic(struct page *page,
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struct iov_iter *i, unsigned long offset, size_t bytes)
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{
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char *kaddr;
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size_t copied;
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kaddr = kmap_atomic(page);
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if (likely(i->nr_segs == 1)) {
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int left;
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char __user *buf = i->iov->iov_base + i->iov_offset;
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left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
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copied = bytes - left;
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} else {
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copied = __iovec_copy_from_user_inatomic(kaddr + offset,
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i->iov, i->iov_offset, bytes);
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}
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kunmap_atomic(kaddr);
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return copied;
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}
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EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
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/*
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* This has the same sideeffects and return value as
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* iov_iter_copy_from_user_atomic().
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* The difference is that it attempts to resolve faults.
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* Page must not be locked.
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*/
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size_t iov_iter_copy_from_user(struct page *page,
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struct iov_iter *i, unsigned long offset, size_t bytes)
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{
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char *kaddr;
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size_t copied;
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kaddr = kmap(page);
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if (likely(i->nr_segs == 1)) {
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int left;
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char __user *buf = i->iov->iov_base + i->iov_offset;
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left = __copy_from_user(kaddr + offset, buf, bytes);
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copied = bytes - left;
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} else {
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copied = __iovec_copy_from_user_inatomic(kaddr + offset,
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i->iov, i->iov_offset, bytes);
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}
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kunmap(page);
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return copied;
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}
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EXPORT_SYMBOL(iov_iter_copy_from_user);
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void iov_iter_advance(struct iov_iter *i, size_t bytes)
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{
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BUG_ON(i->count < bytes);
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if (likely(i->nr_segs == 1)) {
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i->iov_offset += bytes;
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i->count -= bytes;
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} else {
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const struct iovec *iov = i->iov;
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size_t base = i->iov_offset;
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unsigned long nr_segs = i->nr_segs;
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/*
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* The !iov->iov_len check ensures we skip over unlikely
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* zero-length segments (without overruning the iovec).
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*/
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while (bytes || unlikely(i->count && !iov->iov_len)) {
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int copy;
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copy = min(bytes, iov->iov_len - base);
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BUG_ON(!i->count || i->count < copy);
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i->count -= copy;
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bytes -= copy;
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base += copy;
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if (iov->iov_len == base) {
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iov++;
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nr_segs--;
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base = 0;
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}
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}
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i->iov = iov;
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i->iov_offset = base;
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i->nr_segs = nr_segs;
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}
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}
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EXPORT_SYMBOL(iov_iter_advance);
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/*
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* Fault in the first iovec of the given iov_iter, to a maximum length
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* of bytes. Returns 0 on success, or non-zero if the memory could not be
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* accessed (ie. because it is an invalid address).
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*
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* writev-intensive code may want this to prefault several iovecs -- that
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* would be possible (callers must not rely on the fact that _only_ the
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* first iovec will be faulted with the current implementation).
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*/
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int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
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{
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char __user *buf = i->iov->iov_base + i->iov_offset;
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bytes = min(bytes, i->iov->iov_len - i->iov_offset);
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return fault_in_pages_readable(buf, bytes);
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}
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EXPORT_SYMBOL(iov_iter_fault_in_readable);
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/*
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* Return the count of just the current iov_iter segment.
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*/
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size_t iov_iter_single_seg_count(const struct iov_iter *i)
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{
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const struct iovec *iov = i->iov;
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if (i->nr_segs == 1)
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return i->count;
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else
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return min(i->count, iov->iov_len - i->iov_offset);
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}
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EXPORT_SYMBOL(iov_iter_single_seg_count);
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