DragonFly kernel List (threaded) for 2005-03
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vfs_journal.c code questions
I was reading through the vfs_journal.c code and was confused by some
of the code:
/usr/src/sys/kern/vfs_journal.c
In function journal_install_vfs_journal()
. ..
jrecord_init(jo, &jrec, JREC_STREAMID_DISCONT);
jrecord_write(&jrec, JTYPE_ASSOCIATE, 0);
. ..
1) the `streamid' parameter for jrecord_init() is set to
JREC_STREAMID_DISCONT which is defined as 0x0002.
While in function jrecord_init():
...
if (streamid < 0) {
streamid = sid++; /* XXX need to track stream ids! */
if (sid == JREC_STREAMID_JMAX)
sid = JREC_STREAMID_JMIN;
}
jrec->streamid = streamid;
...
So now jrec->streamid is JREC_STREAMID_DISCONT (0x0002).
Shouldn't streamid be some number between JREC_STREAMID_JMIN and
JREC_STREAMID_JMAX?
#define JREC_STREAMID_JMIN 0x0100 /* lowest allowed general id */
#define JREC_STREAMID_JMAX 0x2000 /* (one past the highest allowed id) */
2) then jrecord_write() comes right after jrecord_init() (also in
function journal_install_vfs_journal()):
jrecord_write(&jrec, JTYPE_ASSOCIATE, 0);
In function jrecord_write():
/*
* Try to catch some obvious errors. Nesting records must specify a
* size of 0, and there should be no left-overs from previous operations
* (such as incomplete data writeouts).
*/
KKASSERT(bytes == 0 || (rectype & JMASK_NESTED) == 0);
KKASSERT(jrec->residual == 0);
Then the kernel is going to panic? Actually it's not in practice, so
I am a bit confused :(
Thanks,
Rongsheng
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