Messages in this thread | | | Date | Sat, 1 Jun 2002 13:04:14 -0700 | From | William Lee Irwin III <> | Subject | Re: [patch 12/16] fix race between writeback and unlink |
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Linus Torvalds wrote: >> The general VFS layer really shouldn't have assigned that strogn a meaning >> to "i_nlink" anyway, it's not for the VFS layer to decide (and it only >> causes problems for any non-UNIX-on-a-disk filesystems).
On Sat, Jun 01, 2002 at 12:19:36PM -0700, Andrew Morton wrote: > Yes, I suspect all the inode refcounting, locking, I_FREEING, I_LOCK, etc > could do with a spring clean. Make it a bit more conventional. I'll > discuss with Al when he resurfaces.
I'm somewhat concerned about the protection of ->i_size, since that appears to be accessed in generic_file_read() without any protection against writers to the field. From a quick glance at current 2.5 (it looks like 2.4 has this too) it looks like it's written to by vmtruncate() through notify_change() with the ->i_sem and BKL held at the moment, but generic_file_read() doesn't take either before reading it, and there may be still other writers. I also don't see the anything like read_barrier_depends() for lockless algorithms or any atomic reads. Even on machines with extremely strong memory consistency models like i386, as loff_t is long long, it would seem possible to catch a partial update and see an entirely bogus ->i_size value. It also appears ->i_size is used to provide some protection against reads of truncated pages, which may be unreliable without some protection of ->i_size.
If these issues are not what I believe them to be I would be more than happy to have these impressions corrected.
Cheers, Bill - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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