On Mon, Apr 18, 2005 at 04:31:06PM +0400, Artem B. Bityuckiy wrote: > On Mon, 2005-04-18 at 12:52 +0100, Christoph Hellwig wrote: > > Oh, I thought the problem is that JFFS2 thought an inode was freed when > > it still was in use. So you're problem is actually that it's no in the > > hash anymore but you don't know yet? > Yes, exactly. VFS developers may always say "it is your problem - > redesign JFFS2", but I think it is too late to redesign it.
I don't think it's too late ever ;-) > > Anyway, please explain in detail why you need all this information, what > > errors you see, etc so we can find a way to fix it properly. > Well, I suspect I explained why I need the mutex. If people will find > the explanation vague, I'll make another attempt. > > The error I see is: > > Eep. Trying to read_inode #15601 when it's already in state 2! > > I debugged this a lot before I've realized the reason. And I believe I > know JFFS2 very well to claim that redesigning it is very painful. > > The erroneous code flow is like this: > > kswapd: removes the inode 15601 from the inode hash (inode.c:478). > kswapd: is preempted at inode.c:485 > JFFS2 writer: awakes, runs GC to reclaim some space. > JFFS2 writer: picks a JFFS2 node belonging to the inode 15601 > JFFS2 writer: looks at the inode state, realizes it is in state PRESENT, > i.e. it is in the inode cache (which is wrong). > JFFS2 writer: runs iget() to acquire a pointer to the struct inode of > the inode 15601. > JFFS2 writer: iget() calls ->read_inode(), i.e., jffs2_read_inode(). Why doesn't __wait_on_freeing_inode get called? prune_icache sets I_FREEING before it's dropping the inode lock. Any, this sounds like you'd want to use ilookup because you don't want to read the inode in the cache anyway, right? > JFFS2 writed: JFFS2 is surprised why read_inode() is called for the > already built inode 15601. > > Or may be VFS is buggy, I'm not sure. May be it shouldn't remove inode > from the inode hash in that point (inode.c:487). It sets the I_FREENG > state to the inode being freed, and iget() may wait in find_inode_fast() > while the inode is actually destroyed (inode.c:562). The inode may be > removed from the inode hash later, in dispose_list() (inode.c:292). > > Or may be this isn't a bug but a feature to make the inode_lock less > contended. Not sure, I'm not a VFS guru. Yes, it's a feature. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
