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Preallocation of space

To: linux-xfs@xxxxxxxxxxx
Subject: Preallocation of space
From: monkeyiq <monkeyiq@xxxxxxxxxxxxxxxxxxxxx>
Date: Sun, 2 Sep 2001 04:53:39 +1000
Cc: monkeyiq@xxxxxxxxxxxxxxxxxxxxx
Sender: owner-linux-xfs@xxxxxxxxxxx
I was reading over this again:

And decided that the next feature for ferris to pick on was:

It's an extent-based filesystem, has features like delayed allocation, space 
preallocation and space coallescing on deletion, and goes to great lengths in 
attempting to layout files using the largest extents possible (an "extent" 
being an offset and a length within a file).

So I was reading xfs_mkfile.c line 188 of 277
          flck.l_whence = SEEK_SET;
          flck.l_start  = 0LL;
          flck.l_len    = size;
#if 0
          (void)ioctl(fd, XFS_IOC_RESVSP64, &flck);

I presume that this XFS_IOC_RESVSP64 tells XFS to reserve off a chunk of
space for future use by the file. Are the ioctl() calls for XFS documented
anywhere? /usr/include/xfs/xfs_fs.h and the tool src is all I am using at
the moment. It just struck me as odd that in xfsprogs-1.2.8 the call was
preprocessed out.


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