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Commit 4273b793 authored by Anand Avati's avatar Anand Avati Committed by Miklos Szeredi
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fuse: O_DIRECT support for files 



Implement ->direct_IO() method in aops. The ->direct_IO() method combines
the existing fuse_direct_read/fuse_direct_write methods to implement
O_DIRECT functionality.

Reaching ->direct_IO() in the read path via generic_file_aio_read ensures
proper synchronization with page cache with its existing framework.

Reaching ->direct_IO() in the write path via fuse_file_aio_write is made
to come via generic_file_direct_write() which makes it play nice with
the page cache w.r.t other mmap pages etc.

On files marked 'direct_io' by the filesystem server, IO always follows
the fuse_direct_read/write path. There is no effect of fcntl(O_DIRECT)
and it always succeeds.

On files not marked with 'direct_io' by the filesystem server, the IO
path depends on O_DIRECT flag by the application. This can be passed
at the time of open() as well as via fcntl().

Note that asynchronous O_DIRECT iocb jobs are completed synchronously
always (this has been the case with FUSE even before this patch)

Signed-off-by: default avatarAnand Avati <avati@redhat.com>
Reviewed-by: default avatarJeff Moyer <jmoyer@redhat.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent ac45d613

fs/fuse/dir.c

+0 −3
Original line number Diff line number Diff line
@@ -387,9 +387,6 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, 
	if (fc->no_create)

		return -ENOSYS;



	if (flags & O_DIRECT)

		return -EINVAL;



	forget = fuse_alloc_forget();

	if (!forget)

		return -ENOMEM;

fs/fuse/file.c

+112 −17
Original line number Diff line number Diff line
@@ -194,10 +194,6 @@ int fuse_open_common(struct inode *inode, struct file *file, bool isdir) 
	struct fuse_conn *fc = get_fuse_conn(inode);

	int err;



	/* VFS checks this, but only _after_ ->open() */

	if (file->f_flags & O_DIRECT)

		return -EINVAL;



	err = generic_file_open(inode, file);

	if (err)

		return err;
@@ -932,17 +928,23 @@ static ssize_t fuse_file_aio_write(struct kiocb *iocb, const struct iovec *iov, 
	struct file *file = iocb->ki_filp;

	struct address_space *mapping = file->f_mapping;

	size_t count = 0;

	size_t ocount = 0;

	ssize_t written = 0;

	ssize_t written_buffered = 0;

	struct inode *inode = mapping->host;

	ssize_t err;

	struct iov_iter i;

	loff_t endbyte = 0;



	WARN_ON(iocb->ki_pos != pos);



	err = generic_segment_checks(iov, &nr_segs, &count, VERIFY_READ);

	ocount = 0;

	err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);

	if (err)

		return err;



	count = ocount;



	mutex_lock(&inode->i_mutex);

	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
@@ -962,11 +964,41 @@ static ssize_t fuse_file_aio_write(struct kiocb *iocb, const struct iovec *iov, 


	file_update_time(file);



	if (file->f_flags & O_DIRECT) {

		written = generic_file_direct_write(iocb, iov, &nr_segs,

						    pos, &iocb->ki_pos,

						    count, ocount);

		if (written < 0 || written == count)

			goto out;



		pos += written;

		count -= written;



		iov_iter_init(&i, iov, nr_segs, count, written);

		written_buffered = fuse_perform_write(file, mapping, &i, pos);

		if (written_buffered < 0) {

			err = written_buffered;

			goto out;

		}

		endbyte = pos + written_buffered - 1;



		err = filemap_write_and_wait_range(file->f_mapping, pos,

						   endbyte);

		if (err)

			goto out;



		invalidate_mapping_pages(file->f_mapping,

					 pos >> PAGE_CACHE_SHIFT,

					 endbyte >> PAGE_CACHE_SHIFT);



		written += written_buffered;

		iocb->ki_pos = pos + written_buffered;

	} else {

		iov_iter_init(&i, iov, nr_segs, count, 0);

		written = fuse_perform_write(file, mapping, &i, pos);

		if (written >= 0)

			iocb->ki_pos = pos + written;



	}

out:

	current->backing_dev_info = NULL;

	mutex_unlock(&inode->i_mutex);
@@ -1101,30 +1133,41 @@ static ssize_t fuse_direct_read(struct file *file, char __user *buf, 
	return res;

}



static ssize_t fuse_direct_write(struct file *file, const char __user *buf,

static ssize_t __fuse_direct_write(struct file *file, const char __user *buf,

				   size_t count, loff_t *ppos)

{

	struct inode *inode = file->f_path.dentry->d_inode;

	ssize_t res;



	if (is_bad_inode(inode))

		return -EIO;



	/* Don't allow parallel writes to the same file */

	mutex_lock(&inode->i_mutex);

	res = generic_write_checks(file, ppos, &count, 0);

	if (!res) {

		res = fuse_direct_io(file, buf, count, ppos, 1);

		if (res > 0)

			fuse_write_update_size(inode, *ppos);

	}

	mutex_unlock(&inode->i_mutex);



	fuse_invalidate_attr(inode);



	return res;

}



static ssize_t fuse_direct_write(struct file *file, const char __user *buf,

				 size_t count, loff_t *ppos)

{

	struct inode *inode = file->f_path.dentry->d_inode;

	ssize_t res;



	if (is_bad_inode(inode))

		return -EIO;



	/* Don't allow parallel writes to the same file */

	mutex_lock(&inode->i_mutex);

	res = __fuse_direct_write(file, buf, count, ppos);

	mutex_unlock(&inode->i_mutex);



	return res;

}



static void fuse_writepage_free(struct fuse_conn *fc, struct fuse_req *req)

{

	__free_page(req->pages[0]);
@@ -2077,6 +2120,57 @@ int fuse_notify_poll_wakeup(struct fuse_conn *fc, 
	return 0;

}



static ssize_t fuse_loop_dio(struct file *filp, const struct iovec *iov,

			     unsigned long nr_segs, loff_t *ppos, int rw)

{

	const struct iovec *vector = iov;

	ssize_t ret = 0;



	while (nr_segs > 0) {

		void __user *base;

		size_t len;

		ssize_t nr;



		base = vector->iov_base;

		len = vector->iov_len;

		vector++;

		nr_segs--;



		if (rw == WRITE)

			nr = __fuse_direct_write(filp, base, len, ppos);

		else

			nr = fuse_direct_read(filp, base, len, ppos);



		if (nr < 0) {

			if (!ret)

				ret = nr;

			break;

		}

		ret += nr;

		if (nr != len)

			break;

	}



	return ret;

}





static ssize_t

fuse_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,

			loff_t offset, unsigned long nr_segs)

{

	ssize_t ret = 0;

	struct file *file = NULL;

	loff_t pos = 0;



	file = iocb->ki_filp;

	pos = offset;



	ret = fuse_loop_dio(file, iov, nr_segs, &pos, rw);



	return ret;

}



static const struct file_operations fuse_file_operations = {

	.llseek		= fuse_file_llseek,

	.read		= do_sync_read,
@@ -2120,6 +2214,7 @@ static const struct address_space_operations fuse_file_aops = { 
	.readpages	= fuse_readpages,

	.set_page_dirty	= __set_page_dirty_nobuffers,

	.bmap		= fuse_bmap,

	.direct_IO	= fuse_direct_IO,

};



void fuse_init_file_inode(struct inode *inode)