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

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From: Darrick J. Wong <djwong@xxxxxxxxxx>

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

Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
 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_ */




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