Commit 71be6b49 authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

vfs: add a FALLOC_FL_UNSHARE mode to fallocate to unshare a range of blocks 



Add a new fallocate mode flag that explicitly unshares blocks on
filesystems that support such features.  The new flag can only
be used with an allocate-mode fallocate call.

Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
parent 0a6eab8b

fs/open.c

+5 −0
Original line number Diff line number Diff line
@@ -256,6 +256,11 @@ int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len) 
	    (mode & ~FALLOC_FL_INSERT_RANGE))

		return -EINVAL;



	/* Unshare range should only be used with allocate mode. */

	if ((mode & FALLOC_FL_UNSHARE_RANGE) &&

	    (mode & ~(FALLOC_FL_UNSHARE_RANGE | FALLOC_FL_KEEP_SIZE)))

		return -EINVAL;



	if (!(file->f_mode & FMODE_WRITE))

		return -EBADF;

include/linux/falloc.h

+2 −1
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ struct space_resv { 
					 FALLOC_FL_PUNCH_HOLE |		\

					 FALLOC_FL_COLLAPSE_RANGE |	\

					 FALLOC_FL_ZERO_RANGE |		\

					 FALLOC_FL_INSERT_RANGE)

					 FALLOC_FL_INSERT_RANGE |	\

					 FALLOC_FL_UNSHARE_RANGE)



#endif /* _FALLOC_H_ */

include/uapi/linux/falloc.h

+18 −0
Original line number Diff line number Diff line
@@ -58,4 +58,22 @@ 
 */

#define FALLOC_FL_INSERT_RANGE		0x20



/*

 * FALLOC_FL_UNSHARE_RANGE is used to unshare shared blocks within the

 * file size without overwriting any existing data. The purpose of this

 * call is to preemptively reallocate any blocks that are subject to

 * copy-on-write.

 *

 * Different filesystems may implement different limitations on the

 * granularity of the operation. Most will limit operations to filesystem

 * block size boundaries, but this boundary may be larger or smaller

 * depending on the filesystem and/or the configuration of the filesystem

 * or file.

 *

 * This flag can only be used with allocate-mode fallocate, which is

 * to say that it cannot be used with the punch, zero, collapse, or

 * insert range modes.

 */

#define FALLOC_FL_UNSHARE_RANGE		0x40



#endif /* _UAPI_FALLOC_H_ */