27 messages in org.freebsd.freebsd-hackersRe: How does swap work address spacew...| From | Sent On | Attachments |
|---|---|---|
| Daniel Lang | Jul 5, 2002 4:35 am | |
| David Schultz | Jul 5, 2002 6:34 am | |
| David Schultz | Jul 5, 2002 6:38 am | |
| Terry Lambert | Jul 5, 2002 7:33 am | |
| Daniel Lang | Jul 5, 2002 4:41 pm | |
| Darren Pilgrim | Jul 5, 2002 5:57 pm | |
| Bernd Walter | Jul 5, 2002 7:06 pm | |
| Terry Lambert | Jul 5, 2002 11:12 pm | |
| Matthew Dillon | Jul 6, 2002 1:10 am | |
| Darren Pilgrim | Jul 6, 2002 2:36 pm | |
| Matthew D. Fuller | Jul 6, 2002 2:51 pm | |
| Bernd Walter | Jul 6, 2002 3:06 pm | |
| Darren Pilgrim | Jul 6, 2002 3:42 pm | |
| Terry Lambert | Jul 6, 2002 4:00 pm | |
| Bernd Walter | Jul 6, 2002 4:04 pm | |
| Bernd Walter | Jul 6, 2002 4:13 pm | |
| Matthew Dillon | Jul 6, 2002 4:33 pm | |
| Matthew Dillon | Jul 6, 2002 4:42 pm | |
| Bernd Walter | Jul 6, 2002 5:09 pm | |
| Matthew Dillon | Jul 6, 2002 5:33 pm | |
| Bernd Walter | Jul 6, 2002 5:42 pm | |
| Matthew Dillon | Jul 6, 2002 5:46 pm | |
| Ian Dowse | Jul 6, 2002 5:49 pm | |
| Bernd Walter | Jul 6, 2002 6:21 pm | |
| Darren Pilgrim | Jul 6, 2002 10:01 pm | |
| Matthew Dillon | Jul 6, 2002 10:09 pm | |
| Darren Pilgrim | Jul 6, 2002 10:43 pm |
| Subject: | Re: How does swap work address spacewise? | |
|---|---|---|
| From: | Ian Dowse (iedo...@maths.tcd.ie) | |
| Date: | Jul 6, 2002 5:49:45 pm | |
| List: | org.freebsd.freebsd-hackers | |
In message <2002...@cicely5.cicely.de>, Bernd Walter writes:
I never saw any negative block numbers in on-disc structures. Now I wonder if it was just hidden behind macros. What is the reason to handle it that way? Do you have some code reference for homework?
These logical block numbers are not stored on disk; they are just used by the filesystem code to refer to block numbers within a file relative to the start of the file. The on-disk format uses direct and indirect block pointers to refer to the actual filesystem blocks, and it is easy to get from a lbn to the sequence of indirection blocks necessary to find the on-disk data. See ufs_getlbns() in sys/ufs/ufs/ufs_bmap.c for details.
These are logical block numbers, which are fragment-sized (1K typically)
(lbns are actually in block-sized, not fragment-sized units, since a single file block is always contiguous on the disk even if it does not begin on a disk block boundary or is not a full block in size. Physical UFS block numbers (ufs_daddr_t in the code) are in fragment-sized units.)
Physical block numbers are 512-byte sized, with a range of 2^32 in -stable. This also winds up being 2TB. So increasing the fragment size does not help in -stable.
It's a proven fact that there is a 1T limit somewhere which was explained with physical block numbers beeing signed.
Yes, the daddr_t type is signed, so the real limit for filesystems is 1TB I think.
Ian
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