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iov_iter: massage calling conventions for first_{iovec,bvec}_segment() 

Pass maxsize by reference, return length via the same.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2022-06-21 16:10:37 -04:00
parent dda8e5d17c
commit 59dbd7d090
1 changed files with 18 additions and 24 deletions
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42
lib/iov_iter.c
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@ -1294,8 +1294,7 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i,
/* must be done on non-empty ITER_IOVEC one */
static unsigned long first_iovec_segment(const struct iov_iter *i,
size_t *size, size_t *start,
size_t maxsize)
size_t *size, size_t *start)
{
size_t skip;
long k;
@ -1306,10 +1305,9 @@ static unsigned long first_iovec_segment(const struct iov_iter *i,
if (unlikely(!len))
continue;
if (len > maxsize)
len = maxsize;
if (*size > len)
*size = len;
*start = addr % PAGE_SIZE;
*size = len;
return addr & PAGE_MASK;
}
BUG(); // if it had been empty, we wouldn't get called
@ -1317,19 +1315,17 @@ static unsigned long first_iovec_segment(const struct iov_iter *i,
/* 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,
size_t maxsize)
size_t *size, size_t *start)
{
struct page *page;
size_t skip = i->iov_offset, len;
len = i->bvec->bv_len - skip;
if (len > maxsize)
len = maxsize;
if (*size > len)
*size = len;
skip += i->bvec->bv_offset;
page = i->bvec->bv_page + skip / PAGE_SIZE;
*start = skip % PAGE_SIZE;
*size = len;
return page;
}
@ -1337,7 +1333,6 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
struct page **pages, size_t maxsize, unsigned maxpages,
size_t *start)
{
size_t len;
int n, res;
if (maxsize > i->count)
@ -1356,25 +1351,25 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
if (i->nofault)
gup_flags |= FOLL_NOFAULT;
addr = first_iovec_segment(i, &len, start, maxsize);
n = DIV_ROUND_UP(len + *start, PAGE_SIZE);
addr = first_iovec_segment(i, &maxsize, start);
n = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
if (n > maxpages)
n = maxpages;
res = get_user_pages_fast(addr, n, gup_flags, pages);
if (unlikely(res <= 0))
return res;
return min_t(size_t, len, res * PAGE_SIZE - *start);
return min_t(size_t, maxsize, res * PAGE_SIZE - *start);
}
if (iov_iter_is_bvec(i)) {
struct page *page;
page = first_bvec_segment(i, &len, start, maxsize);
n = DIV_ROUND_UP(len + *start, PAGE_SIZE);
page = first_bvec_segment(i, &maxsize, start);
n = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
if (n > maxpages)
n = maxpages;
for (int k = 0; k < n; k++)
get_page(*pages++ = page++);
return min_t(size_t, len, n * PAGE_SIZE - *start);
return min_t(size_t, maxsize, n * PAGE_SIZE - *start);
}
if (iov_iter_is_pipe(i))
return pipe_get_pages(i, pages, maxsize, maxpages, start);
@ -1469,7 +1464,6 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
size_t *start)
{
struct page **p;
size_t len;
int n, res;
if (maxsize > i->count)
@ -1488,8 +1482,8 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
if (i->nofault)
gup_flags |= FOLL_NOFAULT;
addr = first_iovec_segment(i, &len, start, maxsize);
n = DIV_ROUND_UP(len + *start, PAGE_SIZE);
addr = first_iovec_segment(i, &maxsize, start);
n = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
p = get_pages_array(n);
if (!p)
return -ENOMEM;
@ -1500,19 +1494,19 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
return res;
}
*pages = p;
return min_t(size_t, len, res * PAGE_SIZE - *start);
return min_t(size_t, maxsize, res * PAGE_SIZE - *start);
}
if (iov_iter_is_bvec(i)) {
struct page *page;
page = first_bvec_segment(i, &len, start, maxsize);
n = DIV_ROUND_UP(len + *start, PAGE_SIZE);
page = first_bvec_segment(i, &maxsize, start);
n = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
*pages = p = get_pages_array(n);
if (!p)
return -ENOMEM;
for (int k = 0; k < n; k++)
get_page(*p++ = page++);
return min_t(size_t, len, n * PAGE_SIZE - *start);
return min_t(size_t, maxsize, n * PAGE_SIZE - *start);
}
if (iov_iter_is_pipe(i))
return pipe_get_pages_alloc(i, pages, maxsize, start);