I would like to get the following 3 patches merged soon, because they touch a lot of filesystems but quite trivially. (this clashes trivially with rcu patches if taken out of order, but easily fixable). Where are we going? http://git.kernel.org/?p=linux/kernel/git/npiggin/linux-npiggin.git;a=blob;f=Documentation/filesystems/path-lookup.txt;h=5435c136d0307854761e9aaaa9886e282d67a881;hb=refs/heads/vfs-scale So please review that if you still have doubts about the overall design. I have been toying with pulling rcu-walk first, before dcache scaling. I'm not really happy with it, because the property that d_lock protects d_count and d_seq and all other elements of the dentry really help make it easy to see that concurrency isn't a problem when doing tricky things like converting rcu-and-seqlock based walking into lock-and-refcount based walking mid-way through a path lookup. So while it is _possible_ to use dcache_lock and careful use of atomic_inc_not_zero etc. for these things, that really sucks and is going in totally the wrong direction (rcu-walk dropping is not a completely rare event, so we could end up with more dcache_lock locking in path walk than we have now). -- Remove redundant (actually incorrect, since dcache RCU lookup) dentry locking documentation and point to the canonical document. Signed-off-by: Nick Piggin <npiggin@xxxxxxxxx> --- include/linux/dcache.h | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) Index: linux-2.6/include/linux/dcache.h =================================================================== --- linux-2.6.orig/include/linux/dcache.h 2010-11-09 22:11:00.000000000 +1100 +++ linux-2.6/include/linux/dcache.h 2010-11-09 23:22:52.000000000 +1100 @@ -141,22 +141,16 @@ struct dentry_operations { char *(*d_dname)(struct dentry *, char *, int); }; -/* the dentry parameter passed to d_hash and d_compare is the parent +/* + * Locking rules for dentry_operations callbacks are to be found in + * Documentation/filesystems/Locking. Keep it updated! + * + * the dentry parameter passed to d_hash and d_compare is the parent * directory of the entries to be compared. It is used in case these * functions need any directory specific information for determining * equivalency classes. Using the dentry itself might not work, as it * might be a negative dentry which has no information associated with - * it */ - -/* -locking rules: - big lock dcache_lock d_lock may block -d_revalidate: no no no yes -d_hash no no no yes -d_compare: no yes yes no -d_delete: no yes no no -d_release: no no no yes -d_iput: no no no yes + * it. */ /* d_flags entries */ -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
