Messages in this thread Patch in this message | | | Date | Thu, 7 Jan 1999 16:12:04 -0500 (EST) | From | Alexander Viro <> | Subject | Re: dcache problems with vfat |
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[Sorry for reposting, but it looks like the first try didn't reach the l-k]
OK, I've found it. It's caused by changes in d_invalidate(). Details: After touch a ../b we have the following picture:
- P 3 b H P 0 foo H P 2 <-- cwd a H P 0
Now we are doing cd /tmp/foo/a
cached_lookup() on foo gives
- P 3 b H P 0 foo H P 3 <-- cwd a H P 0
d_invalidate() calls shrink_dcache_parent(). Result being
- P 3 b H P 0 foo H P 2 <-- cwd
Now, old d_invalidate() would decide that it can't do d_drop() since d_count is greater than 1. New one drops it. Rest is trivial. We end up with the following:
- P 4 b H P 0 foo - P 1 <-- cwd foo H P 1 a H P 0
Now we do rm a and shit finally hits the fan: lookup on a gives us
- P 4 b H P 0 foo - P 2 <-- cwd a H P 1 foo H P 1 a H P 0
... and drop_replace_inodes along with d_delete() results in
- P 4 b H P 0 foo - P 2 <-- cwd a H N 0 foo H P 1 a - P 0
i.e. it unhashes dentry with zero d_count _and_ leaves it positive and leaves a new dentry hashed but negative.
cd .. simply does dput() on the unhashed dentry of foo. Nothing interesting - d_count remains positive. Attempt of rmdir doesn't even touch the sucker - lookup gets hashed version.
Summary: changes in d_invalidate() made in 2.1.132 are incorrect; we can't unhash the sucker if it can get children in the future. drop_replace_inodes() is *badly* broken since it doesn't check d_count on aliases. Old d_invalidate() somewhat masked it, but attempt to open something via the short name followed by unlink via long one would leave us with the interesting situation on hands.
Fix: revert changes in d_invalidate(). I.e.
--- dcache.c Tue Jan 5 16:19:12 1999 +++ dcache.c.new Thu Jan 7 16:10:44 1999 @@ -169,7 +169,7 @@ /* Check whether to do a partial shrink_dcache */ if (!list_empty(&dentry->d_subdirs)) { shrink_dcache_parent(dentry); - if (!list_empty(&dentry->d_subdirs)) + if (dentry->d_count>1) return -EBUSY; }
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