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authorAl Viro <viro@zeniv.linux.org.uk>2021-04-25 23:00:48 +0300
committerAl Viro <viro@zeniv.linux.org.uk>2021-06-10 18:45:12 +0300
commit66531c65aa254e77c935785036beb50985d0fe89 (patch)
tree451d1a5c7d1b2040f8fa1233a90eb89477bba4dd /lib
parent3d671ca62a08114810321a2a5e9d3523de5fb1b4 (diff)
downloadlinux-66531c65aa254e77c935785036beb50985d0fe89.tar.xz
iov_iter_npages(): don't bother with iterate_all_kinds()
note that in bvec case pages can be compound ones - we can't just assume that each segment is covered by one (sub)page Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'lib')
-rw-r--r--lib/iov_iter.c88
1 files changed, 54 insertions, 34 deletions
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 3fd331b3b8f2..1c65de175371 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1864,19 +1864,56 @@ size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
}
EXPORT_SYMBOL(hash_and_copy_to_iter);
-int iov_iter_npages(const struct iov_iter *i, int maxpages)
+static int iov_npages(const struct iov_iter *i, int maxpages)
{
- size_t size = i->count;
+ size_t skip = i->iov_offset, size = i->count;
+ const struct iovec *p;
int npages = 0;
- if (!size)
- return 0;
- if (unlikely(iov_iter_is_discard(i)))
- return 0;
+ for (p = i->iov; size; skip = 0, p++) {
+ unsigned offs = offset_in_page(p->iov_base + skip);
+ size_t len = min(p->iov_len - skip, size);
- if (unlikely(iov_iter_is_pipe(i))) {
- struct pipe_inode_info *pipe = i->pipe;
+ 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;
+ /* 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_pipe(i)) {
unsigned int iter_head;
+ int npages;
size_t off;
if (!sanity(i))
@@ -1884,11 +1921,13 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages)
data_start(i, &iter_head, &off);
/* some of this one + all after this one */
- npages = pipe_space_for_user(iter_head, pipe->tail, pipe);
- if (npages >= maxpages)
- return maxpages;
- } else if (unlikely(iov_iter_is_xarray(i))) {
+ npages = pipe_space_for_user(iter_head, i->pipe->tail, i->pipe);
+ return min(npages, maxpages);
+ }
+ if (iov_iter_is_xarray(i)) {
+ size_t size = i->count;
unsigned offset;
+ int npages;
offset = (i->xarray_start + i->iov_offset) & ~PAGE_MASK;
@@ -1900,28 +1939,9 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages)
if (size)
npages++;
}
- if (npages >= maxpages)
- return maxpages;
- } else iterate_all_kinds(i, size, v, ({
- unsigned long p = (unsigned long)v.iov_base;
- npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
- - p / PAGE_SIZE;
- if (npages >= maxpages)
- return maxpages;
- 0;}),({
- npages++;
- if (npages >= maxpages)
- return maxpages;
- }),({
- unsigned long p = (unsigned long)v.iov_base;
- npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE)
- - p / PAGE_SIZE;
- if (npages >= maxpages)
- return maxpages;
- }),
- 0
- )
- return npages;
+ return min(npages, maxpages);
+ }
+ return 0;
}
EXPORT_SYMBOL(iov_iter_npages);