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Subject[PATCH] tmpfs: add support for read_iter and write_iter
Convert tmpfs do_shmem_file_read() to shmem_file_read_iter().
Make file_read_iter_actor() global so tmpfs can use it too: delete
file_read_actor(), which was made global in 2.4.4 for use by tmpfs.
Replace tmpfs generic_file_aio_write() by generic_file_write_iter().

Signed-off-by: Hugh Dickins <hughd@google.com>
---
Please add this to the end of your loop O_DIRECT series. I tested loop
on tmpfs successfully with .direct_IO = shmem_direct_IO() { return 0; }
but that's better left as a patch for separate discussion.

Hmm, I don't see an equivalent of the old fault_in_pages_writeable():
have I missed it, or is that a problem?

include/linux/fs.h | 5 ++-
mm/filemap.c | 42 +----------------------------
mm/shmem.c | 61 +++++++++++++------------------------------
3 files changed, 24 insertions(+), 84 deletions(-)

--- 3.8-dk/include/linux/fs.h 2013-01-29 14:40:40.272041622 -0800
+++ linux/include/linux/fs.h 2013-02-02 20:40:07.316296654 -0800
@@ -2458,8 +2458,9 @@ extern int sb_min_blocksize(struct super
extern int generic_file_mmap(struct file *, struct vm_area_struct *);
extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);
extern int generic_file_remap_pages(struct vm_area_struct *, unsigned long addr,
- unsigned long size, pgoff_t pgoff);
-extern int file_read_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size);
+ unsigned long size, pgoff_t pgoff);
+extern int file_read_iter_actor(read_descriptor_t *desc, struct page *page,
+ unsigned long offset, unsigned long size);
int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk);
extern ssize_t generic_file_aio_read(struct kiocb *, const struct iovec *, unsigned long, loff_t);
extern ssize_t generic_file_read_iter(struct kiocb *, struct iov_iter *,
--- 3.8-dk/mm/filemap.c 2013-01-29 14:40:12.520040962 -0800
+++ linux/mm/filemap.c 2013-02-02 20:40:17.728296902 -0800
@@ -1295,44 +1295,6 @@ out:
file_accessed(filp);
}

-int file_read_actor(read_descriptor_t *desc, struct page *page,
- unsigned long offset, unsigned long size)
-{
- char *kaddr;
- unsigned long left, count = desc->count;
-
- if (size > count)
- size = count;
-
- /*
- * Faults on the destination of a read are common, so do it before
- * taking the kmap.
- */
- if (!fault_in_pages_writeable(desc->arg.buf, size)) {
- kaddr = kmap_atomic(page);
- left = __copy_to_user_inatomic(desc->arg.buf,
- kaddr + offset, size);
- kunmap_atomic(kaddr);
- if (left == 0)
- goto success;
- }
-
- /* Do it the slow way */
- kaddr = kmap(page);
- left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
- kunmap(page);
-
- if (left) {
- size -= left;
- desc->error = -EFAULT;
- }
-success:
- desc->count = count - size;
- desc->written += size;
- desc->arg.buf += size;
- return size;
-}
-
/*
* Performs necessary checks before doing a write
* @iov: io vector request
@@ -1372,8 +1334,8 @@ int generic_segment_checks(const struct
}
EXPORT_SYMBOL(generic_segment_checks);

-static int file_read_iter_actor(read_descriptor_t *desc, struct page *page,
- unsigned long offset, unsigned long size)
+int file_read_iter_actor(read_descriptor_t *desc, struct page *page,
+ unsigned long offset, unsigned long size)
{
struct iov_iter *iter = desc->arg.data;
unsigned long copied = 0;
--- 3.8-dk/mm/shmem.c 2013-01-02 20:27:10.956550061 -0800
+++ linux/mm/shmem.c 2013-02-03 21:21:17.332510148 -0800
@@ -1463,14 +1463,23 @@ shmem_write_end(struct file *file, struc
return copied;
}

-static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor)
+static ssize_t shmem_file_read_iter(struct kiocb *iocb,
+ struct iov_iter *iter, loff_t pos)
{
+ read_descriptor_t desc;
+ loff_t *ppos = &iocb->ki_pos;
+ struct file *filp = iocb->ki_filp;
struct inode *inode = filp->f_path.dentry->d_inode;
struct address_space *mapping = inode->i_mapping;
pgoff_t index;
unsigned long offset;
enum sgp_type sgp = SGP_READ;

+ desc.written = 0;
+ desc.count = iov_iter_count(iter);
+ desc.arg.data = iter;
+ desc.error = 0;
+
/*
* Might this read be for a stacking filesystem? Then when reading
* holes of a sparse file, we actually need to allocate those pages,
@@ -1497,10 +1506,10 @@ static void do_shmem_file_read(struct fi
break;
}

- desc->error = shmem_getpage(inode, index, &page, sgp, NULL);
- if (desc->error) {
- if (desc->error == -EINVAL)
- desc->error = 0;
+ desc.error = shmem_getpage(inode, index, &page, sgp, NULL);
+ if (desc.error) {
+ if (desc.error == -EINVAL)
+ desc.error = 0;
break;
}
if (page)
@@ -1551,13 +1560,13 @@ static void do_shmem_file_read(struct fi
* "pos" here (the actor routine has to update the user buffer
* pointers and the remaining count).
*/
- ret = actor(desc, page, offset, nr);
+ ret = file_read_iter_actor(&desc, page, offset, nr);
offset += ret;
index += offset >> PAGE_CACHE_SHIFT;
offset &= ~PAGE_CACHE_MASK;

page_cache_release(page);
- if (ret != nr || !desc->count)
+ if (ret != nr || !desc.count)
break;

cond_resched();
@@ -1565,40 +1574,8 @@ static void do_shmem_file_read(struct fi

*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, file_read_actor);
- retval += desc.written;
- if (desc.error) {
- retval = retval ?: desc.error;
- break;
- }
- if (desc.count > 0)
- break;
- }
- return retval;
+ return desc.written ? desc.written : desc.error;
}

static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
@@ -2679,8 +2656,8 @@ static const struct file_operations shme
.llseek = shmem_file_llseek,
.read = do_sync_read,
.write = do_sync_write,
- .aio_read = shmem_file_aio_read,
- .aio_write = generic_file_aio_write,
+ .read_iter = shmem_file_read_iter,
+ .write_iter = generic_file_write_iter,
.fsync = noop_fsync,
.splice_read = shmem_file_splice_read,
.splice_write = generic_file_splice_write,

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