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Date: Mon, 04 Feb 2013 11:24:26 -0600
From: Dave Kleikamp <dave.kleikamp@...cle.com>
To: Hugh Dickins <hughd@...gle.com>
CC: Al Viro <viro@...iv.linux.org.uk>, Zach Brown <zab@...bo.net>,
"Maxim V. Patlasov" <mpatlasov@...allels.com>,
Jeff Moyer <jmoyer@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tmpfs: add support for read_iter and write_iter
On 02/04/2013 12:15 AM, Hugh Dickins wrote:
> 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@...gle.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.
Thanks!
> Hmm, I don't see an equivalent of the old fault_in_pages_writeable():
> have I missed it, or is that a problem?
That's a good question. I think adding back fault_in_pages_writeable()
and the surrounding logic into ii_iovec_copy_to_user() would be worthwhile.
> 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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