FALLOC_FL_ZERO_RANGE was added in Linux 3.14, for zeroing ranges in the allocated space in a file. Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx> --- man2/fallocate.2 | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/man2/fallocate.2 b/man2/fallocate.2 index b31bbde..df31782 100644 --- a/man2/fallocate.2 +++ b/man2/fallocate.2 @@ -124,6 +124,45 @@ Btrfs (since Linux 3.7) .IP * tmpfs (since Linux 3.5) .\" commit 83e4fa9c16e4af7122e31be3eca5d57881d236fe +.SS Zeroing file space +Specifying +.BR FALLOC_FL_ZERO_RANGE +flag (available since Linux 3.14) in +.I mode +zeroes space in the byte range starting at +.I offset +and continuing for +.I len +bytes. +Within the specified range, blocks are preallocated for the regions +that span the holes in the file. After a successful call, +subsequent reads from this range will return zeroes. + +Zeroing is done within the file system preferably by converting range into +unwritten extents which requires very little IO to be issued. + +If the +.B FALLOC_FL_KEEP_SIZE +flag is specified in +.IR mode , +the behavior of the call is similar, +but the file size will not be changed even if +.IR offset + len +is greater than the file size. This behaviour is the same as when +preallocating space with +.B FALLOC_FL_KEEP_SIZE +specified. + +Not all filesystems support +.BR FALLOC_FL_ZERO_RANGE ; +if a filesystem doesn't support the operation, an error is returned. +The operation is supported on at least the following filesystems +.IP * 3 +XFS (since Linux 2.14) +.\" commit 376ba313147b4172f3e8cf620b9fb591f3e8cdfa +.IP * +ext4 (since Linux 3.14) +.\" commit b8a8684502a0fc852afa0056c6bb2a9273f6fcc0 .SH RETURN VALUE On success, .BR fallocate () @@ -193,6 +232,8 @@ Or: .I mode specifies .BR FALLOC_FL_PUNCH_HOLE +or +.BR FALLOC_FL_ZERO_RANGE and the file referred to by .I fd -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
