Messages in this thread Patch in this message | | | Date | Tue, 04 May 2004 17:00:15 +1000 | From | Greg Banks <> | Subject | Re: d_splice_alias() problem. |
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Neil Brown wrote: > > > * 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) { > > One problem with this is that (in include/asm-i386/atomic.h at least): > static __inline__ void atomic_inc(atomic_t *v)
Ok, how about this...it's portable, and not racy, but may perturb the logic slightly by also taking dentries off the unused list in the case where they already had d_count>=1. I'm not sure how significant that is. In any case this also passes my tests.
--- linux.orig/fs/dcache.c Mon May 3 21:46:30 2004 +++ linux/fs/dcache.c Tue May 4 14:34:44 2004 @@ -256,7 +256,7 @@ static inline struct dentry * __dget_locked(struct dentry *dentry) { atomic_inc(&dentry->d_count); - if (atomic_read(&dentry->d_count) == 1) { + if (!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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