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Update to comments describing block allocation policy.

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Submitted by: Bruce Evans
This commit is contained in:
Kirk McKusick 2013-07-14 18:44:33 +00:00
parent fc4153c26f
commit fdd9a6f478
1 changed files with 6 additions and 7 deletions
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13
sys/ufs/ffs/ffs_alloc.c
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@ -1196,7 +1196,8 @@ ffs_dirpref(pip)
/*
* Select the desired position for the next block in a file. The file is
* logically divided into sections. The first section is composed of the
* direct blocks. Each additional section contains fs_maxbpg blocks.
* direct blocks and the next fs_maxbpg blocks. Each additional section
* contains fs_maxbpg blocks.
*
* If no blocks have been allocated in the first section, the policy is to
* request a block in the same cylinder group as the inode that describes
@ -1214,14 +1215,12 @@ ffs_dirpref(pip)
* cylinder group from which the previous allocation was made. The sweep
* continues until a cylinder group with greater than the average number
* of free blocks is found. If the allocation is for the first block in an
* indirect block, the information on the previous allocation is unavailable;
* here a best guess is made based upon the logical block number being
* allocated.
* indirect block or the previous block is a hole, then the information on
* the previous allocation is unavailable; here a best guess is made based
* on the logical block number being allocated.
*
* If a section is already partially allocated, the policy is to
* contiguously allocate fs_maxcontig blocks. The end of one of these
* contiguous blocks and the beginning of the next is laid out
* contiguously if possible.
* allocate blocks contiguously within the section if possible.
*/
ufs2_daddr_t
ffs_blkpref_ufs1(ip, lbn, indx, bap)