Re: [PATCH] NFS - Fix for Infinite loop during syncing

[Steve Dickson <SteveD@redhat.com>]

Trond Myklebust wrote:

>m=E5 den 13.12.2004 Klokka 15:23 (-0500) skreiv Steve Dickson:
> =20
>
>>It was brought to my attention that following series of events
>>would cause an infinite loop in the 2.4 nfs kernels.
>>
>>1) Mount the fileystem with acregmin=3D1,acregmax=3D1 from two clients.
>>2) On client 1, create a process that continuously writes to a file.
>>3) On client 2, remove that file that is being written
>>4) On client 1, interrupted out of the writing process (which is failin=
g
>>     with ESTALEs) and type sync
>>
>>The sync process loops in wait_on_locked(), when called from
>>sync_inodes_sb(), since the "broken" inode can not be cleared
>>from the locked inode list.
>>   =20
>>
>
>Isn't this pretty much a generic problem of mmapped files? AFAICS, sync
>can loop here no matter what filesystem one is using.
> =20
>
maybe, but these were not mmapped files... here is perl script I used

open $file, "> filetje.$$" or die "Open failed: $!";
while ( 1 ) {
   print $file time(), " The quick brown fox jumps over the lazy dog,=20
1234567890\n"
}

>If you use ordinary writes, then all is well, since the
>nfs_revalidate_inode() in nfs_file_write() should set the NFS_INO_STALE
>flag for you.
> =20
>
Right... nfs_revalidate_inode() does "break" the inode only after a (in=20
this case)
seconded ESTALE  failure .... By setting NFS_INO_STALE in nfs_write_done(=
)
it breaks the inode earlier, which means the nfs_revalidate_inode() is=20
not even
tried.

Now that I think about it... probably makes sense to set NFS_INO_STALE in
nfs_commit_done() as well... From my debugging, it just seems the=20
earlier we
break the inode... the better....

steved.



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