[PATCH 3/5] vfs: add a zero-initialization mode to fallocate

Darrick J. Wong
2021-09-18T01:31:03Z

From: Darrick J. Wong <djwong@kernel.org>

Add a new mode to fallocate to zero-initialize all the storage backing a
file.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
fs/open.c | 5 +++++
include/linux/falloc.h | 1 +
include/uapi/linux/falloc.h | 9 +++++++++
3 files changed, 15 insertions(+)

diff --git a/fs/open.c b/fs/open.c
index daa324606a41..230220b8f67a 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;

+ /* Zeroinit should only be used by itself and keep size must be set. */
+ if ((mode & FALLOC_FL_ZEROINIT_RANGE) &&
+ (mode != (FALLOC_FL_ZEROINIT_RANGE | FALLOC_FL_KEEP_SIZE)))
+ 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)))
diff --git a/include/linux/falloc.h b/include/linux/falloc.h
index f3f0b97b1675..4597b416667b 100644
--- a/include/linux/falloc.h
+++ b/include/linux/falloc.h
@@ -29,6 +29,7 @@ struct space_resv {
FALLOC_FL_PUNCH_HOLE | \
FALLOC_FL_COLLAPSE_RANGE | \
FALLOC_FL_ZERO_RANGE | \
+ FALLOC_FL_ZEROINIT_RANGE | \
FALLOC_FL_INSERT_RANGE | \
FALLOC_FL_UNSHARE_RANGE)

diff --git a/include/uapi/linux/falloc.h b/include/uapi/linux/falloc.h
index 51398fa57f6c..8144403b6102 100644
--- a/include/uapi/linux/falloc.h
+++ b/include/uapi/linux/falloc.h
@@ -77,4 +77,13 @@
*/
#define FALLOC_FL_UNSHARE_RANGE 0x40

+/*
+ * FALLOC_FL_ZEROINIT_RANGE is used to reinitialize storage backing a file by
+ * writing zeros to it. Subsequent read and writes should not fail due to any
+ * previous media errors. Blocks must be not be shared or require copy on
+ * write. Holes and unwritten extents are left untouched. This mode must be
+ * used with FALLOC_FL_KEEP_SIZE.
+ */
+#define FALLOC_FL_ZEROINIT_RANGE 0x80
+
#endif /* _UAPI_FALLOC_H_ */