New helper: append_pipe(). Extends the last buffer if possible,
allocates a new one otherwise. Returns page and offset in it
on success, NULL on failure. iov_iter is advanced past the
data we've got.
Use that instead of push_pipe() in copy-to-pipe primitives;
they get simpler that way. Handling of short copy (in "mc" one)
is done simply by iov_iter_revert() - iov_iter is in consistent
state after that one, so we can use that.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
lib/iov_iter.c | 159 +++++++++++++++++++++++++++++--------------------
1 file changed, 93 insertions(+), 66 deletions(-)
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 924854c2a7ce..d23e4ccd0564 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -259,6 +259,44 @@ static void push_page(struct pipe_inode_info *pipe, struct page *page,
get_page(page);
}
+static inline bool allocated(struct pipe_buffer *buf)
+{
+ return buf->ops == &default_pipe_buf_ops;
+}
+
+static struct page *append_pipe(struct iov_iter *i, size_t size, size_t *off)
+{
+ struct pipe_inode_info *pipe = i->pipe;
+ size_t offset = i->iov_offset;
+ struct pipe_buffer *buf;
+ struct page *page;
+
+ if (offset && offset < PAGE_SIZE) {
+ // some space in the last buffer; can we add to it?
+ buf = pipe_buf(pipe, pipe->head - 1);
+ if (allocated(buf)) {
+ size = min_t(size_t, size, PAGE_SIZE - offset);
+ buf->len += size;
+ i->iov_offset += size;
+ i->count -= size;
+ *off = offset;
+ return buf->page;
+ }
+ }
+ // OK, we need a new buffer
+ *off = 0;
+ size = min_t(size_t, size, PAGE_SIZE);
+ if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
+ return NULL;
+ page = push_anon(pipe, size);
+ if (!page)
+ return NULL;
+ i->head = pipe->head - 1;
+ i->iov_offset = size;
+ i->count -= size;
+ return page;
+}
+
static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
@@ -396,11 +434,6 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
}
EXPORT_SYMBOL(iov_iter_init);
-static inline bool allocated(struct pipe_buffer *buf)
-{
- return buf->ops == &default_pipe_buf_ops;
-}
-
static inline void data_start(const struct iov_iter *i,
unsigned int *iter_headp, size_t *offp)
{
@@ -459,28 +492,26 @@ static size_t push_pipe(struct iov_iter *i, size_t size,
static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
struct iov_iter *i)
{
- struct pipe_inode_info *pipe = i->pipe;
- unsigned int p_mask = pipe->ring_size - 1;
- unsigned int i_head;
size_t n, off;
- if (!sanity(i))
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+ if (unlikely(!bytes))
return 0;
- bytes = n = push_pipe(i, bytes, &i_head, &off);
- if (unlikely(!n))
+ if (!sanity(i))
return 0;
- do {
+
+ n = bytes;
+ while (n) {
+ struct page *page = append_pipe(i, n, &off);
size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
- memcpy_to_page(pipe->bufs[i_head & p_mask].page, off, addr, chunk);
- i->head = i_head;
- i->iov_offset = off + chunk;
- n -= chunk;
+ if (!page)
+ break;
+ memcpy_to_page(page, off, addr, chunk);
addr += chunk;
- off = 0;
- i_head++;
- } while (n);
- i->count -= bytes;
+ n -= chunk;
+ }
return bytes;
}
@@ -494,31 +525,32 @@ static __wsum csum_and_memcpy(void *to, const void *from, size_t len,
static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
struct iov_iter *i, __wsum *sump)
{
- struct pipe_inode_info *pipe = i->pipe;
- unsigned int p_mask = pipe->ring_size - 1;
__wsum sum = *sump;
size_t off = 0;
- unsigned int i_head;
size_t r;
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+ if (unlikely(!bytes))
+ return 0;
+
if (!sanity(i))
return 0;
- bytes = push_pipe(i, bytes, &i_head, &r);
while (bytes) {
+ struct page *page = append_pipe(i, bytes, &r);
size_t chunk = min_t(size_t, bytes, PAGE_SIZE - r);
- char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
+ char *p;
+
+ if (!page)
+ break;
+ p = kmap_local_page(page);
sum = csum_and_memcpy(p + r, addr + off, chunk, sum, off);
kunmap_local(p);
- i->head = i_head;
- i->iov_offset = r + chunk;
- bytes -= chunk;
off += chunk;
- r = 0;
- i_head++;
+ bytes -= chunk;
}
*sump = sum;
- i->count -= off;
return off;
}
@@ -550,39 +582,35 @@ static int copyout_mc(void __user *to, const void *from, size_t n)
static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
struct iov_iter *i)
{
- struct pipe_inode_info *pipe = i->pipe;
- unsigned int p_mask = pipe->ring_size - 1;
- unsigned int i_head;
- unsigned int valid = pipe->head;
- size_t n, off, xfer = 0;
+ size_t off, xfer = 0;
+
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+ if (unlikely(!bytes))
+ return 0;
if (!sanity(i))
return 0;
- n = push_pipe(i, bytes, &i_head, &off);
- while (n) {
- size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
- char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
+ while (bytes) {
+ struct page *page = append_pipe(i, bytes, &off);
+ size_t chunk = min_t(size_t, bytes, PAGE_SIZE - off);
unsigned long rem;
+ char *p;
+
+ if (!page)
+ break;
+ p = kmap_local_page(page);
rem = copy_mc_to_kernel(p + off, addr + xfer, chunk);
chunk -= rem;
kunmap_local(p);
- if (chunk) {
- i->head = i_head;
- i->iov_offset = off + chunk;
- xfer += chunk;
- valid = i_head + 1;
- }
+ xfer += chunk;
+ bytes -= chunk;
if (rem) {
- pipe->bufs[i_head & p_mask].len -= rem;
- pipe_discard_from(pipe, valid);
+ iov_iter_revert(i, rem);
break;
}
- n -= chunk;
- off = 0;
- i_head++;
}
- i->count -= xfer;
return xfer;
}
@@ -769,30 +797,29 @@ EXPORT_SYMBOL(copy_page_from_iter);
static size_t pipe_zero(size_t bytes, struct iov_iter *i)
{
- struct pipe_inode_info *pipe = i->pipe;
- unsigned int p_mask = pipe->ring_size - 1;
- unsigned int i_head;
size_t n, off;
- if (!sanity(i))
+ if (unlikely(bytes > i->count))
+ bytes = i->count;
+ if (unlikely(!bytes))
return 0;
- bytes = n = push_pipe(i, bytes, &i_head, &off);
- if (unlikely(!n))
+ if (!sanity(i))
return 0;
- do {
+ n = bytes;
+ while (n) {
+ struct page *page = append_pipe(i, n, &off);
size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
- char *p = kmap_local_page(pipe->bufs[i_head & p_mask].page);
+ char *p;
+
+ if (page)
+ break;
+ p = kmap_local_page(page);
memset(p + off, 0, chunk);
kunmap_local(p);
- i->head = i_head;
- i->iov_offset = off + chunk;
n -= chunk;
- off = 0;
- i_head++;
- } while (n);
- i->count -= bytes;
+ }
return bytes;
}
--
2.30.2
