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author | mpp <mpp@FreeBSD.org> | 2002-01-09 11:43:48 +0000 |
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committer | mpp <mpp@FreeBSD.org> | 2002-01-09 11:43:48 +0000 |
commit | 52a504f88d0ffe375d2be6da101ccf6a08176b54 (patch) | |
tree | 3ce5e662efc4ab60de20e79ba7cd33a2a01b26e1 /share/man/man9/buf.9 | |
parent | ff2f125aa58758bad73ad0977bba4c53cddf1b3c (diff) | |
download | FreeBSD-src-52a504f88d0ffe375d2be6da101ccf6a08176b54.zip FreeBSD-src-52a504f88d0ffe375d2be6da101ccf6a08176b54.tar.gz |
ispell sweep of share/man/man9/*.
Diffstat (limited to 'share/man/man9/buf.9')
-rw-r--r-- | share/man/man9/buf.9 | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/share/man/man9/buf.9 b/share/man/man9/buf.9 index c68f7f9..9d8b643 100644 --- a/share/man/man9/buf.9 +++ b/share/man/man9/buf.9 @@ -80,11 +80,11 @@ they are no longer needed but often keeps the 'struct buf' structure instantiated and even bp->b_pages array instantiated despite having unmapped them from KVM. If a page making up a VM buffer is about to undergo I/O, the system typically unmaps it from KVM and replaces the page in the b_pages[] -array with a placemarker called bogus_page. The placemarker forces any kernel +array with a place-marker called bogus_page. The place-marker forces any kernel subsystems referencing the associated struct buf to re-lookup the associated -page. I believe the placemarker hack is used to allow sophisticated devices +page. I believe the place-marker hack is used to allow sophisticated devices such as filesystem devices to remap underlying pages in order to deal with, -for example, remapping a file fragment into a file block. +for example, re-mapping a file fragment into a file block. .Pp VM buffers are used to track I/O operations within the kernel. Unfortunately, the I/O implementation is also somewhat of a hack because the kernel wants @@ -94,7 +94,7 @@ can create confusion within filesystem devices that use delayed-writes because you wind up with pages marked clean that are actually still dirty. If not treated carefully, these pages could be thrown away! Indeed, a number of serious bugs related to this hack were not fixed until the 2.2.8/3.0 release. -The kernel uses an instantiated VM buffer (i.e. struct buf) to placemark pages +The kernel uses an instantiated VM buffer (i.e. struct buf) to place-mark pages in this special state. The buffer is typically flagged B_DELWRI. When a device no longer needs a buffer it typically flags it as B_RELBUF. Due to the underlying pages being marked clean, the B_DELWRI|B_RELBUF combination must |