introduce copy_page_to_iter, kill loop over iovec in generic_file_aio_read()
generic_file_aio_read() was looping over the target iovec, with loop over
(source) pages nested inside that. Just set an iov_iter up and pass *that*
to do_generic_file_aio_read(). With copy_page_to_iter() doing all work
of mapping and copying a page to iovec and advancing iov_iter.
Switch shmem_file_aio_read() to the same and kill file_read_actor(), while
we are at it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/mm/shmem.c b/mm/shmem.c
index 9398e6c..17d3799d 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1462,13 +1462,25 @@
return copied;
}
-static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc)
+static ssize_t shmem_file_aio_read(struct kiocb *iocb,
+ const struct iovec *iov, unsigned long nr_segs, loff_t pos)
{
- struct inode *inode = file_inode(filp);
+ struct file *file = iocb->ki_filp;
+ struct inode *inode = file_inode(file);
struct address_space *mapping = inode->i_mapping;
pgoff_t index;
unsigned long offset;
enum sgp_type sgp = SGP_READ;
+ int error;
+ ssize_t retval;
+ size_t count;
+ loff_t *ppos = &iocb->ki_pos;
+ struct iov_iter iter;
+
+ retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
+ if (retval)
+ return retval;
+ iov_iter_init(&iter, iov, nr_segs, count, 0);
/*
* Might this read be for a stacking filesystem? Then when reading
@@ -1496,10 +1508,10 @@
break;
}
- desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
- if (desc->error) {
- if (desc->error == -EINVAL)
- desc->error = 0;
+ error = shmem_getpage(inode, index, &page, sgp, NULL);
+ if (error) {
+ if (error == -EINVAL)
+ error = 0;
break;
}
if (page)
@@ -1543,61 +1555,26 @@
/*
* Ok, we have the page, and it's up-to-date, so
* now we can copy it to user space...
- *
- * The actor routine returns how many bytes were actually used..
- * NOTE! This may not be the same as how much of a user buffer
- * we filled up (we may be padding etc), so we can only update
- * "pos" here (the actor routine has to update the user buffer
- * pointers and the remaining count).
*/
- ret = file_read_actor(desc, page, offset, nr);
+ ret = copy_page_to_iter(page, offset, nr, &iter);
+ retval += ret;
offset += ret;
index += offset >> PAGE_CACHE_SHIFT;
offset &= ~PAGE_CACHE_MASK;
page_cache_release(page);
- if (ret != nr || !desc->count)
+ if (!iov_iter_count(&iter))
break;
-
+ if (ret < nr) {
+ error = -EFAULT;
+ break;
+ }
cond_resched();
}
*ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset;
- file_accessed(filp);
-}
-
-static ssize_t shmem_file_aio_read(struct kiocb *iocb,
- const struct iovec *iov, unsigned long nr_segs, loff_t pos)
-{
- struct file *filp = iocb->ki_filp;
- ssize_t retval;
- unsigned long seg;
- size_t count;
- loff_t *ppos = &iocb->ki_pos;
-
- retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
- if (retval)
- return retval;
-
- for (seg = 0; seg < nr_segs; seg++) {
- read_descriptor_t desc;
-
- desc.written = 0;
- desc.arg.buf = iov[seg].iov_base;
- desc.count = iov[seg].iov_len;
- if (desc.count == 0)
- continue;
- desc.error = 0;
- do_shmem_file_read(filp, ppos, &desc);
- retval += desc.written;
- if (desc.error) {
- retval = retval ?: desc.error;
- break;
- }
- if (desc.count > 0)
- break;
- }
- return retval;
+ file_accessed(file);
+ return retval ? retval : error;
}
static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,