Messages in this thread Patches in this message | | | Date | Mon, 03 May 2004 22:02:01 +1000 | From | Greg Banks <> | Subject | Re: d_splice_alias() problem. |
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Neil Brown wrote: > > This problem can be resolved by making sure that an inode never has > both a connected and a disconnected dentry. > > This is already the case for directories (as they must only have one > dentry), but it is not the case for non-directories. > > The following patch tries to address this. It is a "technology > preview" in that the only testing I have done is that it compiles OK. > > Please consider reviewing it to see if it makes sense.
It does, and it fixes one of the dcache bugs that was tripping my debug code. Here are a couple more.
* Logic bug in d_splice_alias() forgets to clear the DCACHE_DISCONNECTED flag when a lookup connects a disconnected dentry. Fix is (relative to Neil's patch):
--- linux.orig/fs/dcache.c Mon May 3 21:46:30 2004 +++ linux/fs/dcache.c Mon May 3 21:49:07 2004 @@ -894,6 +895,7 @@ new = __d_find_alias(inode, 1); if (new) { BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED)); + new->d_flags &= ~DCACHE_DISCONNECTED; spin_unlock(&dcache_lock); security_d_instantiate(new, inode); d_rehash(dentry);
* Dentry_stat.nr_unused can be be spuriously decremented when dput() races with __dget_unlocked(). Eventual result is nr_unused<0 and kswapd loops. This is the problem I mentioned earlier. Note that this is not an NFS-specific problem. Fix is:
--- linux.orig/fs/dcache.c Mon May 3 21:46:30 2004 +++ linux/fs/dcache.c Mon May 3 21:49:07 2004 @@ -255,8 +255,8 @@ static inline struct dentry * __dget_locked(struct dentry *dentry) { - atomic_inc(&dentry->d_count); - if (atomic_read(&dentry->d_count) == 1) { + if (atomic_inc(&dentry->d_count) == 1) { + BUG_ON(list_empty(&dentry->d_lru)); dentry_stat.nr_unused--; list_del_init(&dentry->d_lru); } @@ -663,6 +663,7 @@ if (gfp_mask & __GFP_FS) prune_dcache(nr); } + BUG_ON(dentry_stat.nr_unused < 0); return dentry_stat.nr_unused; } Greg. -- Greg Banks, R&D Software Engineer, SGI Australian Software Group. I don't speak for SGI. - 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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