reserving contiguous files

["Rick Smith" <rgsmith72@xxxxxxxxxxx>]

Hello,
    I am trying to write sequences of contiguous files in XFS to minimize 
the drive head seeks that must occur during file reads. Using the 
XFS_RESVSP64 ioctl to reserve the set of files ahead of time, I am able to 
get individual files allocated with contiguous extents. However, the 
allocation of one file versus another (reserved immediately after each 
other) seems to be somewhat erratic. Is there a way to guarantee or further 
lock the allocation of one file with respect to another in a contiguous 
manner? Looking at xfs_vnodeops.c and xfs_bmap.c could this be possibly be 
achieved by initializing the firstfsb structure in xfs_alloc_file_space() 
only in the first reserve call for a group allocation? The value of this 
structure could be maintained for consecutive calls to allow the contiguous 
allocation of a group of files based on the preceeding reserve ioctl. This 
behavior could be added as an additional ioctl call (RESVSP64CONTIG?) to 
maintain the current working code.
    I am going to experiment with this, but I would appreciate 
suggestions/comments. Thanks.

Rick Smith

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