Lukas, Thanks for the patch. Two general comments: * The text does not explain what zeroing file space is about and why one would do it. For example, I'm a little unclear after reading it whether FALLOC_FL_ZERO_RANGE will create a hole in a file. * Some entries should probably be added to ERRORS. Could you fix both of those and resubmit? Note that I've just pushed some changes to the page for FALLOC_FL_COLLAPSE_RANGE, so you may want to pull the latest version to ensure there are no conflicts. Cheers, Michael On 04/17/2014 03:30 PM, Lukas Czerner wrote: > 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 > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
