Ping, Lukáš! On Fri, Apr 18, 2014 at 6:21 PM, Lukáš Czerner <lczerner@xxxxxxxxxx> wrote: > On Fri, 18 Apr 2014, Michael Kerrisk (man-pages) wrote: > >> Date: Fri, 18 Apr 2014 17:49:48 +0200 >> From: "Michael Kerrisk (man-pages)" <mtk.manpages@xxxxxxxxx> >> To: Lukas Czerner <lczerner@xxxxxxxxxx> >> Cc: mtk.manpages@xxxxxxxxx, linux-man@xxxxxxxxxxxxxxx, >> linux-fsdevel@xxxxxxxxxxxxxxx >> Subject: Re: [PATCH] fallocate.2: Document FALLOC_FL_ZERO_RANGE >> >> 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. > > It is saying that blocks are preallocated for the regions that span > holes in the file. And there isn't anything saying about punching a > hole into the file. But I guess I can be more clear about it. > >> * Some entries should probably be added to ERRORS. >> >> Could you fix both of those and resubmit? > > Sure I'll do that next week. > >> >> 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
