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Commit 0b5da8db authored by Ravishankar N's avatar Ravishankar N Committed by Miklos Szeredi
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fuse: add support for SEEK_HOLE and SEEK_DATA in lseek 

A useful performance improvement for accessing virtual machine images
via FUSE mount.

See https://bugzilla.redhat.com/show_bug.cgi?id=1220173

 for a use-case
for glusterFS.

Signed-off-by: default avatarRavishankar N <ravishankar@redhat.com>
Signed-off-by: default avatarMiklos Szeredi <miklos@szeredi.hu>
parent 3ca8138f

fs/fuse/file.c

+65 −8
Original line number Diff line number Diff line
@@ -2231,20 +2231,77 @@ static sector_t fuse_bmap(struct address_space *mapping, sector_t block) 
	return err ? 0 : outarg.block;

}



static loff_t fuse_lseek(struct file *file, loff_t offset, int whence)

{

	struct inode *inode = file->f_mapping->host;

	struct fuse_conn *fc = get_fuse_conn(inode);

	struct fuse_file *ff = file->private_data;

	FUSE_ARGS(args);

	struct fuse_lseek_in inarg = {

		.fh = ff->fh,

		.offset = offset,

		.whence = whence

	};

	struct fuse_lseek_out outarg;

	int err;



	if (fc->no_lseek)

		goto fallback;



	args.in.h.opcode = FUSE_LSEEK;

	args.in.h.nodeid = ff->nodeid;

	args.in.numargs = 1;

	args.in.args[0].size = sizeof(inarg);

	args.in.args[0].value = &inarg;

	args.out.numargs = 1;

	args.out.args[0].size = sizeof(outarg);

	args.out.args[0].value = &outarg;

	err = fuse_simple_request(fc, &args);

	if (err) {

		if (err == -ENOSYS) {

			fc->no_lseek = 1;

			goto fallback;

		}

		return err;

	}



	return vfs_setpos(file, outarg.offset, inode->i_sb->s_maxbytes);



fallback:

	err = fuse_update_attributes(inode, NULL, file, NULL);

	if (!err)

		return generic_file_llseek(file, offset, whence);

	else

		return err;

}



static loff_t fuse_file_llseek(struct file *file, loff_t offset, int whence)

{

	loff_t retval;

	struct inode *inode = file_inode(file);



	switch (whence) {

	case SEEK_SET:

	case SEEK_CUR:

		 /* No i_mutex protection necessary for SEEK_CUR and SEEK_SET */

	if (whence == SEEK_CUR || whence == SEEK_SET)

		return generic_file_llseek(file, offset, whence);



		retval = generic_file_llseek(file, offset, whence);

		break;

	case SEEK_END:

		mutex_lock(&inode->i_mutex);

		retval = fuse_update_attributes(inode, NULL, file, NULL);

		if (!retval)

			retval = generic_file_llseek(file, offset, whence);

		mutex_unlock(&inode->i_mutex);

		break;

	case SEEK_HOLE:

	case SEEK_DATA:

		mutex_lock(&inode->i_mutex);

		retval = fuse_lseek(file, offset, whence);

		mutex_unlock(&inode->i_mutex);

		break;

	default:

		retval = -EINVAL;

	}



	return retval;

}

fs/fuse/fuse_i.h

+3 −0
Original line number Diff line number Diff line
@@ -605,6 +605,9 @@ struct fuse_conn { 
	/** Does the filesystem support asynchronous direct-IO submission? */

	unsigned async_dio:1;



	/** Is lseek not implemented by fs? */

	unsigned no_lseek:1;



	/** The number of requests waiting for completion */

	atomic_t num_waiting;

include/uapi/linux/fuse.h

+16 −1
Original line number Diff line number Diff line
@@ -102,6 +102,9 @@ 
 *  - add ctime and ctimensec to fuse_setattr_in

 *  - add FUSE_RENAME2 request

 *  - add FUSE_NO_OPEN_SUPPORT flag

 *

 *  7.24

 *  - add FUSE_LSEEK for SEEK_HOLE and SEEK_DATA support

 */



#ifndef _LINUX_FUSE_H
@@ -137,7 +140,7 @@ 
#define FUSE_KERNEL_VERSION 7



/** Minor version number of this interface */

#define FUSE_KERNEL_MINOR_VERSION 23

#define FUSE_KERNEL_MINOR_VERSION 24



/** The node ID of the root inode */

#define FUSE_ROOT_ID 1
@@ -358,6 +361,7 @@ enum fuse_opcode { 
	FUSE_FALLOCATE     = 43,

	FUSE_READDIRPLUS   = 44,

	FUSE_RENAME2       = 45,

	FUSE_LSEEK         = 46,



	/* CUSE specific operations */

	CUSE_INIT          = 4096,
@@ -758,4 +762,15 @@ struct fuse_notify_retrieve_in { 
/* Device ioctls: */

#define FUSE_DEV_IOC_CLONE	_IOR(229, 0, uint32_t)



struct fuse_lseek_in {

	uint64_t	fh;

	uint64_t	offset;

	uint32_t	whence;

	uint32_t	padding;

};



struct fuse_lseek_out {

	uint64_t	offset;

};



#endif /* _LINUX_FUSE_H */