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fix copy_page_from_iter() for compound destinations 

had been broken for ITER_BVEC et.al. since ever (OK, v3.17 when
ITER_BVEC had first appeared)...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2022-07-29 12:54:53 -04:00
parent c7d57ab163
commit c03f05f183
1 changed files with 18 additions and 4 deletions
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22
lib/iov_iter.c
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@ -738,13 +738,27 @@ EXPORT_SYMBOL(copy_page_to_iter);
size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
if (page_copy_sane(page, offset, bytes)) {
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 wanted = _copy_from_iter(kaddr + offset, bytes, i);
size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
n = _copy_from_iter(kaddr + offset, n, i);
kunmap_local(kaddr);
return wanted;
res += n;
bytes -= n;
if (!bytes || !n)
break;
offset += n;
if (offset == PAGE_SIZE) {
page++;
offset = 0;
}
}
return 0;
return res;
}
EXPORT_SYMBOL(copy_page_from_iter);