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Re: Preallocation and Ferris

To: linux-xfs@xxxxxxxxxxx
Subject: Re: Preallocation and Ferris
From: monkeyiq <monkeyiq@xxxxxxxxxxxxxxxxxxxxx>
Date: Mon, 4 Feb 2002 20:55:05 +1000
Cc: monkeyiq <monkeyiq@xxxxxxxxxxxxxxxxxxxxx>
Sender: owner-linux-xfs@xxxxxxxxxxx
  After looking at the xfs_bmap code a little and working out my
next move I noticed in xfs_fs.h

struct getbmapx {
        __s64           bmv_offset;     /* file offset of segment in blocks */
        __s64           bmv_block;      /* starting block (64-bit daddr_t)  */
        __s64           bmv_length;     /* length of segment, blocks        */
        __s32           bmv_count;      /* # of entries in array incl. 1st  */
        __s32           bmv_entries;    /* # of entries filled in (output). */
        __s32           bmv_iflags;     /* input flags (1st structure)      */
        __s32           bmv_oflags;     /* output flags (after 1st structure)*/
        __s32           bmv_unused1;    /* future use                       */
        __s32           bmv_unused2;    /* future use                       */

/*      bmv_iflags values - set by XFS_IOC_GETBMAPX caller.     */
#define BMV_IF_ATTRFORK         0x1     /* return attr fork rather than data */
#define BMV_IF_NO_DMAPI_READ    0x2     /* Do not generate DMAPI read event  */
#define BMV_IF_PREALLOC         0x4     /* rtn status BMV_OF_PREALLOC if req */
#ifdef __KERNEL__
#define BMV_IF_EXTENDED 0x40000000      /* getpmapx if set */

/*      bmv_oflags values - returned for for each non-header segment */
#define BMV_OF_PREALLOC         0x1     /* segment = unwritten pre-allocation */

I have tried using BMV_IF_PREALLOC and just dumping out 
for each extent listed though its *always* 0. This is 
using the official 1.0.2 (IIRC) 2.4.14 kernel stuff and

I suspect that maybe the prealloc stuff is not being sent to 
userland and I can not work out how to get xfs_bmap to
show me a flag for an extent that is preallocation.

BTW I now have preallocation switch working for file creation
in ferris :) it shows a 0 byte file with an extent that is 
the preallocation size rounded up to next block.

How "experimental" is the real time file support? I am wondering
if there are other sweet xfs features that I should make available
in ferris :) The interface to make preallocated files uses the
ferriscreate GUI, http://witme.sourceforge.net/ferriscreate.paper2001/
I will make new screenshots of that soon using preallocation and 
anything else I throw in there for my xfs and other enjoyment.

Though I would like to expose the final preallocation extent as 
fake EA in ferris to allow a easy interface to expand/reduce 
preallocation from a cute GUI ;)

BTW what is the mood on acceptance of a patch for xfs_bmap to have
an --xml option to dump the same info from -v as an XML 1.0 document?
this would make it nice and easy to make an extent viewer as either
a gtk+ app or a php4 app.


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