Messages in this thread | | | From | Nikita Danilov <> | Date | Thu, 2 Oct 2003 14:51:10 +0400 | Subject | Re: 2.6.0-test6 crash while reading files in /proc/fs/reiserfs/sda1 |
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viro@parcelfarce.linux.theplanet.co.uk writes: > On Thu, Oct 02, 2003 at 02:08:26PM +0400, Nikita Danilov wrote: > > What about creating fake struct vfsmount for /proc/fs/reiserfs/<devname> > > and attaching it to the super block of /<mountpoint>? After all > > /proc/fs/reiserfs/<devname> is just a view into /<mountpoint>. This will > > automatically guarantee that /<mountpoint> cannot be unmounted while > > files in /proc/fs/reiserfs/<devname> are opened. Will this screw up > > dcache? > > I don't see what it would buy you - you get to revalidate the pointer to > vfsmount instead of revalidating pointer to superblock, which is not easier.
I thought that opening procfs file would do mntget() that will pin super block of host file system. Wouldn't it?
> sget()-based revalidation actually works OK - see previous reply for details. > With optimistic sget() (which we should've done a long time ago) it's > actually cheaper than your original "search by dev_t" - you are looking > only through reiserfs superblocks instead of all superblocks in system.
Yes, I agree.
> > > Yes, possible. I had similar problem in reiser4 also: for some seq_file, > > x_start() allocated some data structure (struct x_struct) that is used > > by x_next(), x_show(), and is deallocated in x_stop(). As x_struct is > > per read invocation rather than per file it cannot be stored in seq_file > > itself. I had to resort to returning x_struct from x_start() and passing > > it without change through x_next()'s. Thing actually changed by x_next() > > was embedded in x_struct. Last x_next() had to deallocate x_struct and > > to return NULL (much like your example above). > > Umm... And what's the problem with that? If your context is created by > ->start() and is needed by ->next() and ->stop(), the above is obvious > solution - you are already passing opaque pointer through that sequence, > so that's about as straightforward as it gets...
It looks unnatural to return constant from ->next(), hiding mutable part inside.
Also code duplication in ->next() and ->stop(). No objective reasons, but new interface will provide more clean (and intuitive to me) separation of error reporting, iteration context, and iteration cookie.
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