[PATCH 02/63] vfs: add a FALLOC_FL_UNSHARE mode to fallocate to unshare a range of blocks
From: Darrick J. Wong <hidden>
Date: 2016-09-30 03:05:52
Also in:
linux-fsdevel
Subsystem:
filesystems (vfs and infrastructure), the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
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 <redacted> --- fs/open.c | 5 +++++ include/linux/falloc.h | 3 ++- include/uapi/linux/falloc.h | 18 ++++++++++++++++++ 3 files changed, 25 insertions(+), 1 deletion(-)
diff --git a/fs/open.c b/fs/open.c
index 4fd6e25..d58525d 100644
--- a/fs/open.c
+++ b/fs/open.c@@ -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;
diff --git a/include/linux/falloc.h b/include/linux/falloc.h
index 9961110..7494dc6 100644
--- a/include/linux/falloc.h
+++ b/include/linux/falloc.h@@ -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_ */
diff --git a/include/uapi/linux/falloc.h b/include/uapi/linux/falloc.h
index 3e445a7..b075f60 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_ */