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author | Al Viro <viro@zeniv.linux.org.uk> | 2016-04-14 19:52:13 -0400 |
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committer | Al Viro <viro@zeniv.linux.org.uk> | 2016-05-02 19:47:51 -0400 |
commit | 85c7f81041d57cfe9dc97f4680d5586b54534a39 (patch) | |
tree | 16415f1241c9fdc7b279d860d53e60c9c8a9e3fb /include | |
parent | 0568d705b0087751f0c085c0a665aa3e954c810d (diff) | |
download | linux-stable-85c7f81041d57cfe9dc97f4680d5586b54534a39.tar.gz linux-stable-85c7f81041d57cfe9dc97f4680d5586b54534a39.tar.bz2 linux-stable-85c7f81041d57cfe9dc97f4680d5586b54534a39.zip |
beginning of transition to parallel lookups - marking in-lookup dentries
marked as such when (would be) parallel lookup is about to pass them
to actual ->lookup(); unmarked when
* __d_add() is about to make it hashed, positive or not.
* __d_move() (from d_splice_alias(), directly or via
__d_unalias()) puts a preexisting dentry in its place
* in caller of ->lookup() if it has escaped all of the
above. Bug (WARN_ON, actually) if it reaches the final dput()
or d_instantiate() while still marked such.
As the result, we are guaranteed that for as long as the flag is
set, dentry will
* remain negative unhashed with positive refcount
* never have its ->d_alias looked at
* never have its ->d_lru looked at
* never have its ->d_parent and ->d_name changed
Right now we have at most one such for any given parent directory.
With parallel lookups that restriction will weaken to
* only exist when parent is locked shared
* at most one with given (parent,name) pair (comparison of
names is according to ->d_compare())
* only exist when there's no hashed dentry with the same
(parent,name)
Transition will take the next several commits; unfortunately, we'll
only be able to switch to rwsem at the end of this series. The
reason for not making it a single patch is to simplify review.
New primitives: d_in_lookup() (a predicate checking if dentry is in
the in-lookup state) and d_lookup_done() (tells the system that
we are done with lookup and if it's still marked as in-lookup, it
should cease to be such).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/dcache.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 4bb4de8d95ea..9a7aa890b642 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -232,6 +232,8 @@ struct dentry_operations { #define DCACHE_ENCRYPTED_WITH_KEY 0x04000000 /* dir is encrypted with a valid key */ #define DCACHE_OP_REAL 0x08000000 +#define DCACHE_PAR_LOOKUP 0x10000000 /* being looked up (with parent locked shared) */ + extern seqlock_t rename_lock; /* @@ -367,6 +369,22 @@ static inline void dont_mount(struct dentry *dentry) spin_unlock(&dentry->d_lock); } +extern void __d_lookup_done(struct dentry *); + +static inline int d_in_lookup(struct dentry *dentry) +{ + return dentry->d_flags & DCACHE_PAR_LOOKUP; +} + +static inline void d_lookup_done(struct dentry *dentry) +{ + if (unlikely(d_in_lookup(dentry))) { + spin_lock(&dentry->d_lock); + __d_lookup_done(dentry); + spin_unlock(&dentry->d_lock); + } +} + extern void dput(struct dentry *); static inline bool d_managed(const struct dentry *dentry) |