Annotation of wikisrc/projects/project/ffs-discard.mdwn, revision 1.2

1.1       dholland    1: [[!template id=project
                      2: 
                      3: title="Discard for FFS"
                      4: 
                      5: contact="""
                      6: [tech-kern](mailto:tech-kern@NetBSD.org)
                      7: """
                      8: 
                      9: mentors="""
                     10: """
                     11: 
                     12: category="filesystems"
                     13: difficulty="medium"
                     14: duration="2-3 months"
                     15: 
                     16: description="""
1.2     ! dholland   17: The fdiscard system call, and the file-system-level VOP_DISCARD operation
1.1       dholland   18: backing it, allow dropping ranges of blocks from files to create
                     19: sparse files with holes.
                     20: This is a simple generalization of truncate.
                     21: 
                     22: Discard is not currently implemented for FFS; implement it.
                     23: (For regular files.)
                     24: It should be possible to do so by generalizing the existing truncate
                     25: code; this should be not super-difficult, but somewhat messy.
                     26: 
1.2     ! dholland   27: Note that it's important (for both the WAPBL and non-WAPBL cases) to
        !            28: preserve the on-disk invariants needed for successful crash recovery.
        !            29: 
1.1       dholland   30: """
                     31: 
                     32: ]]

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