(implemented by ffs_reallocblks_ufs[12]) relocates the file's blocks so as to cluster them together into a contiguous set of blocks on the disk. When the cluster crosses the boundary into the first indirect block, the first indirect block is initially allocated in a position immediately following the last direct block. Block reallocation would usually destroy locality by moving the indirect block out of the way to keep the data blocks contiguous. This change compensates for this problem by noting that the first indirect block should be left immediately following the last direct block. It then tries to start a new cluster of contiguous blocks (referenced by the indirect block) immediately following the indirect block. We should also do this for other indirect block boundaries, but it is only important for the first one. Suggested by: Bruce Evans MFC: 2 weeks |
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