new helper: copy_page_from_iter()

parallel to copy_page_to_iter().  pipe_write() switched to it (and became
->write_iter()).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 99 insertions, 110 deletions

diff --git a/fs/pipe.c b/fs/pipe.c
index 05ccb00cb407..21981e58e2a6 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -116,50 +116,6 @@ void pipe_wait(struct pipe_inode_info *pipe)
         pipe_lock(pipe);
 }
 
-static int
-pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
-                        int atomic)
-{
-        unsigned long copy;
-
-        while (len > 0) {
-                while (!iov->iov_len)
-                        iov++;
-                copy = min_t(unsigned long, len, iov->iov_len);
-
-                if (atomic) {
-                        if (__copy_from_user_inatomic(to, iov->iov_base, copy))
-                                return -EFAULT;
-                } else {
-                        if (copy_from_user(to, iov->iov_base, copy))
-                                return -EFAULT;
-                }
-                to += copy;
-                len -= copy;
-                iov->iov_base += copy;
-                iov->iov_len -= copy;
-        }
-        return 0;
-}
-
-/*
- * Pre-fault in the user memory, so we can use atomic copies.
- */
-static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
-{
-        while (!iov->iov_len)
-                iov++;
-
-        while (len > 0) {
-                unsigned long this_len;
-
-                this_len = min_t(unsigned long, len, iov->iov_len);
-                fault_in_pages_readable(iov->iov_base, this_len);
-                len -= this_len;
-                iov++;
-        }
-}
-
 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
                                   struct pipe_buffer *buf)
 {
@@ -380,24 +336,19 @@ static inline int is_packetized(struct file *file)
 }
 
 static ssize_t
-pipe_write(struct kiocb *iocb, const struct iovec *_iov,
-            unsigned long nr_segs, loff_t ppos)
+pipe_write(struct kiocb *iocb, struct iov_iter *from)
 {
         struct file *filp = iocb->ki_filp;
         struct pipe_inode_info *pipe = filp->private_data;
-        ssize_t ret;
-        int do_wakeup;
-        struct iovec *iov = (struct iovec *)_iov;
-        size_t total_len;
+        ssize_t ret = 0;
+        int do_wakeup = 0;
+        size_t total_len = iov_iter_count(from);
         ssize_t chars;
 
-        total_len = iov_length(iov, nr_segs);
         /* Null write succeeds. */
         if (unlikely(total_len == 0))
                 return 0;
 
-        do_wakeup = 0;
-        ret = 0;
         __pipe_lock(pipe);
 
         if (!pipe->readers) {
@@ -416,38 +367,19 @@ pipe_write(struct kiocb *iocb, const struct iovec *_iov,
                 int offset = buf->offset + buf->len;
 
                 if (ops->can_merge && offset + chars <= PAGE_SIZE) {
-                        int error, atomic = 1;
-                        void *addr;
-
-                        error = ops->confirm(pipe, buf);
+                        int error = ops->confirm(pipe, buf);
                         if (error)
                                 goto out;
 
-                        iov_fault_in_pages_read(iov, chars);
-redo1:
-                        if (atomic)
-                                addr = kmap_atomic(buf->page);
-                        else
-                                addr = kmap(buf->page);
-                        error = pipe_iov_copy_from_user(offset + addr, iov,
-                                                        chars, atomic);
-                        if (atomic)
-                                kunmap_atomic(addr);
-                        else
-                                kunmap(buf->page);
-                        ret = error;
-                        do_wakeup = 1;
-                        if (error) {
-                                if (atomic) {
-                                        atomic = 0;
-                                        goto redo1;
-                                }
+                        ret = copy_page_from_iter(buf->page, offset, chars, from);
+                        if (unlikely(ret < chars)) {
+                                error = -EFAULT;
                                 goto out;
                         }
+                        do_wakeup = 1;
                         buf->len += chars;
-                        total_len -= chars;
                         ret = chars;
-                        if (!total_len)
+                        if (!iov_iter_count(from))
                                 goto out;
                 }
         }
@@ -466,8 +398,7 @@ redo1:
                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
                         struct pipe_buffer *buf = pipe->bufs + newbuf;
                         struct page *page = pipe->tmp_page;
-                        char *src;
-                        int error, atomic = 1;
+                        int copied;
 
                         if (!page) {
                                 page = alloc_page(GFP_HIGHUSER);
@@ -483,40 +414,19 @@ redo1:
                          * FIXME! Is this really true?
                          */
                         do_wakeup = 1;
-                        chars = PAGE_SIZE;
-                        if (chars > total_len)
-                                chars = total_len;
-
-                        iov_fault_in_pages_read(iov, chars);
-redo2:
-                        if (atomic)
-                                src = kmap_atomic(page);
-                        else
-                                src = kmap(page);
-
-                        error = pipe_iov_copy_from_user(src, iov, chars,
-                                                        atomic);
-                        if (atomic)
-                                kunmap_atomic(src);
-                        else
-                                kunmap(page);
-
-                        if (unlikely(error)) {
-                                if (atomic) {
-                                        atomic = 0;
-                                        goto redo2;
-                                }
+                        copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
+                        if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
                                 if (!ret)
-                                        ret = error;
+                                        ret = -EFAULT;
                                 break;
                         }
-                        ret += chars;
+                        ret += copied;
 
                         /* Insert it into the buffer array */
                         buf->page = page;
                         buf->ops = &anon_pipe_buf_ops;
                         buf->offset = 0;
-                        buf->len = chars;
+                        buf->len = copied;
                         buf->flags = 0;
                         if (is_packetized(filp)) {
                                 buf->ops = &packet_pipe_buf_ops;
@@ -525,8 +435,7 @@ redo2:
                         pipe->nrbufs = ++bufs;
                         pipe->tmp_page = NULL;
 
-                        total_len -= chars;
-                        if (!total_len)
+                        if (!iov_iter_count(from))
                                 break;
                 }
                 if (bufs < pipe->buffers)
@@ -1040,8 +949,8 @@ const struct file_operations pipefifo_fops = {
         .llseek         = no_llseek,
         .read           = new_sync_read,
         .read_iter      = pipe_read,
-        .write          = do_sync_write,
-        .aio_write      = pipe_write,
+        .write          = new_sync_write,
+        .write_iter     = pipe_write,
         .poll           = pipe_poll,
         .unlocked_ioctl = pipe_ioctl,
         .release        = pipe_release,
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 532f59d0adbb..66012352d333 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -68,6 +68,8 @@ int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
 size_t iov_iter_single_seg_count(const struct iov_iter *i);
 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
                          struct iov_iter *i);
+size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
+                         struct iov_iter *i);
 unsigned long iov_iter_alignment(const struct iov_iter *i);
 void iov_iter_init(struct iov_iter *i, int direction, const struct iovec *iov,
                         unsigned long nr_segs, size_t count);
diff --git a/mm/iov_iter.c b/mm/iov_iter.c
index a5c691c1a283..081e3273085b 100644
--- a/mm/iov_iter.c
+++ b/mm/iov_iter.c
@@ -82,6 +82,84 @@ done:
 }
 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)
+{
+        size_t skip, copy, left, wanted;
+        const struct iovec *iov;
+        char __user *buf;
+        void *kaddr, *to;
+
+        if (unlikely(bytes > i->count))
+                bytes = i->count;
+
+        if (unlikely(!bytes))
+                return 0;
+
+        wanted = bytes;
+        iov = i->iov;
+        skip = i->iov_offset;
+        buf = iov->iov_base + skip;
+        copy = min(bytes, iov->iov_len - skip);
+
+        if (!fault_in_pages_readable(buf, copy)) {
+                kaddr = kmap_atomic(page);
+                to = kaddr + offset;
+
+                /* first chunk, usually the only one */
+                left = __copy_from_user_inatomic(to, buf, copy);
+                copy -= left;
+                skip += copy;
+                to += copy;
+                bytes -= copy;
+
+                while (unlikely(!left && bytes)) {
+                        iov++;
+                        buf = iov->iov_base;
+                        copy = min(bytes, iov->iov_len);
+                        left = __copy_from_user_inatomic(to, buf, copy);
+                        copy -= left;
+                        skip = copy;
+                        to += copy;
+                        bytes -= copy;
+                }
+                if (likely(!bytes)) {
+                        kunmap_atomic(kaddr);
+                        goto done;
+                }
+                offset = to - kaddr;
+                buf += copy;
+                kunmap_atomic(kaddr);
+                copy = min(bytes, iov->iov_len - skip);
+        }
+        /* Too bad - revert to non-atomic kmap */
+        kaddr = kmap(page);
+        to = kaddr + offset;
+        left = __copy_from_user(to, buf, copy);
+        copy -= left;
+        skip += copy;
+        to += copy;
+        bytes -= copy;
+        while (unlikely(!left && bytes)) {
+                iov++;
+                buf = iov->iov_base;
+                copy = min(bytes, iov->iov_len);
+                left = __copy_from_user(to, buf, copy);
+                copy -= left;
+                skip = copy;
+                to += copy;
+                bytes -= copy;
+        }
+        kunmap(page);
+done:
+        i->count -= wanted - bytes;
+        i->nr_segs -= iov - i->iov;
+        i->iov = iov;
+        i->iov_offset = skip;
+        return wanted - bytes;
+}
+EXPORT_SYMBOL(copy_page_from_iter);
+
 static size_t __iovec_copy_from_user_inatomic(char *vaddr,
                         const struct iovec *iov, size_t base, size_t bytes)
 {