CVS commit: src/sys/fs/puffs

[Antti Kantee <pooka%netbsd.org@localhost>]

Module Name:    src
Committed By:   pooka
Date:           Fri Jan 19 14:59:50 UTC 2007

Modified Files:
        src/sys/fs/puffs: puffs_vnops.c

Log Message:
In case the fs server is in the kernel doing an operation on a
completely different file system, we still might re-enter the same
puffs fs in case we execute something on the other file system,
which wants to get a new vnode and ends up recycling a puffs vnode
for the purpose.  In this case the fs server will sleep in the
kernel until it itself handles the operation .... which of course
is a slightly unlikely event.

After analyzing the path from getcleanvnode() to the vnode cemetary,
identify that fsync and putpages (strategy) are the ones in danger
of striking a deadlock deal.  Abuse the vnode flag VXLOCK to tell
them "this vnode is irreversably going to meet its maker, don't
care about user server return values" (failure is not acceptable
down the vgonel() path) and issue the respective operations as
Fire-And-Forget (FAF) operations.  no wait -> no deadlock.

This of course is a "fix" skating on thin ice.  A better, more
generic solution is already in sight, but will take more effort to
implement.


To generate a diff of this commit:
cvs rdiff -r1.34 -r1.35 src/sys/fs/puffs/puffs_vnops.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.