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authorDarrick J. Wong <darrick.wong@oracle.com>2016-10-03 09:11:14 -0700
committerDarrick J. Wong <darrick.wong@oracle.com>2016-10-03 09:11:14 -0700
commit71be6b4942dd64bc17728f82f787be98fd8afed7 (patch)
treec5a219e8c9d574051b01551d6e24012519213a03 /include/uapi
parent0a6eab8bd4e0120d49511acbb294797d96ef9e4a (diff)
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: Darrick J. Wong <darrick.wong@oracle.com>
Diffstat (limited to 'include/uapi')
-rw-r--r--include/uapi/linux/falloc.h18
1 files changed, 18 insertions, 0 deletions
diff --git a/include/uapi/linux/falloc.h b/include/uapi/linux/falloc.h
index 3e445a760f14..b075f601919b 100644
--- a/include/uapi/linux/falloc.h
+++ b/include/uapi/linux/falloc.h
@@ -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_ */