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fs: dcache scale lru
Add a new lock, dcache_lru_lock, to protect the dcache LRU list from concurrent modification. d_lru is also protected by d_lock, which allows LRU lists to be accessed without the lru lock, using RCU in future patches. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin
parent
789680d1ee
commit
2304450783
114
fs/dcache.c
114
fs/dcache.c
@ -37,11 +37,19 @@
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/*
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* Usage:
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* dcache_hash_lock protects dcache hash table, s_anon lists
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* dcache_hash_lock protects:
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* - the dcache hash table, s_anon lists
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* dcache_lru_lock protects:
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* - the dcache lru lists and counters
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* d_lock protects:
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* - d_flags
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* - d_name
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* - d_lru
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*
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* Ordering:
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* dcache_lock
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* dentry->d_lock
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* dcache_lru_lock
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* dcache_hash_lock
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*
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* if (dentry1 < dentry2)
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@ -52,6 +60,7 @@ int sysctl_vfs_cache_pressure __read_mostly = 100;
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EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
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static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_hash_lock);
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static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
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__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
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__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
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@ -154,28 +163,38 @@ static void dentry_iput(struct dentry * dentry)
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}
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/*
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* dentry_lru_(add|del|move_tail) must be called with dcache_lock held.
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* dentry_lru_(add|del|move_tail) must be called with d_lock held.
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*/
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static void dentry_lru_add(struct dentry *dentry)
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{
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if (list_empty(&dentry->d_lru)) {
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spin_lock(&dcache_lru_lock);
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list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
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dentry->d_sb->s_nr_dentry_unused++;
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dentry_stat.nr_unused++;
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spin_unlock(&dcache_lru_lock);
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}
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}
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static void __dentry_lru_del(struct dentry *dentry)
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{
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list_del_init(&dentry->d_lru);
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dentry->d_sb->s_nr_dentry_unused--;
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dentry_stat.nr_unused--;
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}
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static void dentry_lru_del(struct dentry *dentry)
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{
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if (!list_empty(&dentry->d_lru)) {
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list_del_init(&dentry->d_lru);
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dentry->d_sb->s_nr_dentry_unused--;
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dentry_stat.nr_unused--;
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spin_lock(&dcache_lru_lock);
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__dentry_lru_del(dentry);
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spin_unlock(&dcache_lru_lock);
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}
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}
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static void dentry_lru_move_tail(struct dentry *dentry)
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{
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spin_lock(&dcache_lru_lock);
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if (list_empty(&dentry->d_lru)) {
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list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
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dentry->d_sb->s_nr_dentry_unused++;
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@ -183,6 +202,7 @@ static void dentry_lru_move_tail(struct dentry *dentry)
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} else {
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list_move_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
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}
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spin_unlock(&dcache_lru_lock);
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}
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/**
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@ -192,6 +212,8 @@ static void dentry_lru_move_tail(struct dentry *dentry)
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* The dentry must already be unhashed and removed from the LRU.
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*
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* If this is the root of the dentry tree, return NULL.
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*
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* dcache_lock and d_lock must be held by caller, are dropped by d_kill.
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*/
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static struct dentry *d_kill(struct dentry *dentry)
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__releases(dentry->d_lock)
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@ -383,13 +405,22 @@ int d_invalidate(struct dentry * dentry)
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EXPORT_SYMBOL(d_invalidate);
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/* This should be called _only_ with dcache_lock held */
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static inline struct dentry * __dget_locked(struct dentry *dentry)
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static inline struct dentry * __dget_locked_dlock(struct dentry *dentry)
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{
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atomic_inc(&dentry->d_count);
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dentry_lru_del(dentry);
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return dentry;
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}
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static inline struct dentry * __dget_locked(struct dentry *dentry)
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{
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atomic_inc(&dentry->d_count);
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spin_lock(&dentry->d_lock);
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dentry_lru_del(dentry);
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spin_unlock(&dentry->d_lock);
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return dentry;
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}
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struct dentry * dget_locked(struct dentry *dentry)
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{
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return __dget_locked(dentry);
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@ -465,7 +496,7 @@ restart:
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list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
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spin_lock(&dentry->d_lock);
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if (!atomic_read(&dentry->d_count)) {
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__dget_locked(dentry);
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__dget_locked_dlock(dentry);
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__d_drop(dentry);
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spin_unlock(&dentry->d_lock);
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spin_unlock(&dcache_lock);
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@ -489,7 +520,6 @@ EXPORT_SYMBOL(d_prune_aliases);
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static void prune_one_dentry(struct dentry * dentry)
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__releases(dentry->d_lock)
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__releases(dcache_lock)
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__acquires(dcache_lock)
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{
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__d_drop(dentry);
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dentry = d_kill(dentry);
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@ -498,15 +528,16 @@ static void prune_one_dentry(struct dentry * dentry)
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* Prune ancestors. Locking is simpler than in dput(),
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* because dcache_lock needs to be taken anyway.
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*/
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spin_lock(&dcache_lock);
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while (dentry) {
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if (!atomic_dec_and_lock(&dentry->d_count, &dentry->d_lock))
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spin_lock(&dcache_lock);
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if (!atomic_dec_and_lock(&dentry->d_count, &dentry->d_lock)) {
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spin_unlock(&dcache_lock);
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return;
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}
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dentry_lru_del(dentry);
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__d_drop(dentry);
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dentry = d_kill(dentry);
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spin_lock(&dcache_lock);
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}
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}
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@ -516,21 +547,31 @@ static void shrink_dentry_list(struct list_head *list)
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while (!list_empty(list)) {
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dentry = list_entry(list->prev, struct dentry, d_lru);
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dentry_lru_del(dentry);
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if (!spin_trylock(&dentry->d_lock)) {
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spin_unlock(&dcache_lru_lock);
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cpu_relax();
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spin_lock(&dcache_lru_lock);
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continue;
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}
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__dentry_lru_del(dentry);
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/*
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* We found an inuse dentry which was not removed from
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* the LRU because of laziness during lookup. Do not free
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* it - just keep it off the LRU list.
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*/
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spin_lock(&dentry->d_lock);
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if (atomic_read(&dentry->d_count)) {
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spin_unlock(&dentry->d_lock);
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continue;
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}
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spin_unlock(&dcache_lru_lock);
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prune_one_dentry(dentry);
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/* dentry->d_lock was dropped in prune_one_dentry() */
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cond_resched_lock(&dcache_lock);
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/* dcache_lock and dentry->d_lock dropped */
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spin_lock(&dcache_lock);
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spin_lock(&dcache_lru_lock);
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}
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}
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@ -551,32 +592,36 @@ static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
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int cnt = *count;
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spin_lock(&dcache_lock);
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relock:
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spin_lock(&dcache_lru_lock);
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while (!list_empty(&sb->s_dentry_lru)) {
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dentry = list_entry(sb->s_dentry_lru.prev,
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struct dentry, d_lru);
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BUG_ON(dentry->d_sb != sb);
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if (!spin_trylock(&dentry->d_lock)) {
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spin_unlock(&dcache_lru_lock);
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cpu_relax();
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goto relock;
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}
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/*
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* If we are honouring the DCACHE_REFERENCED flag and the
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* dentry has this flag set, don't free it. Clear the flag
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* and put it back on the LRU.
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*/
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if (flags & DCACHE_REFERENCED) {
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spin_lock(&dentry->d_lock);
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if (dentry->d_flags & DCACHE_REFERENCED) {
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dentry->d_flags &= ~DCACHE_REFERENCED;
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list_move(&dentry->d_lru, &referenced);
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spin_unlock(&dentry->d_lock);
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cond_resched_lock(&dcache_lock);
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continue;
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}
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if (flags & DCACHE_REFERENCED &&
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dentry->d_flags & DCACHE_REFERENCED) {
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dentry->d_flags &= ~DCACHE_REFERENCED;
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list_move(&dentry->d_lru, &referenced);
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spin_unlock(&dentry->d_lock);
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} else {
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list_move_tail(&dentry->d_lru, &tmp);
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spin_unlock(&dentry->d_lock);
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if (!--cnt)
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break;
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}
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list_move_tail(&dentry->d_lru, &tmp);
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if (!--cnt)
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break;
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cond_resched_lock(&dcache_lock);
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/* XXX: re-add cond_resched_lock when dcache_lock goes away */
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}
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*count = cnt;
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@ -584,6 +629,7 @@ static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
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if (!list_empty(&referenced))
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list_splice(&referenced, &sb->s_dentry_lru);
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spin_unlock(&dcache_lru_lock);
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spin_unlock(&dcache_lock);
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}
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@ -679,10 +725,12 @@ void shrink_dcache_sb(struct super_block *sb)
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LIST_HEAD(tmp);
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spin_lock(&dcache_lock);
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spin_lock(&dcache_lru_lock);
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while (!list_empty(&sb->s_dentry_lru)) {
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list_splice_init(&sb->s_dentry_lru, &tmp);
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shrink_dentry_list(&tmp);
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}
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spin_unlock(&dcache_lru_lock);
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spin_unlock(&dcache_lock);
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}
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EXPORT_SYMBOL(shrink_dcache_sb);
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@ -701,7 +749,9 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
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/* detach this root from the system */
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spin_lock(&dcache_lock);
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spin_lock(&dentry->d_lock);
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dentry_lru_del(dentry);
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spin_unlock(&dentry->d_lock);
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__d_drop(dentry);
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spin_unlock(&dcache_lock);
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@ -715,7 +765,9 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
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spin_lock(&dcache_lock);
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list_for_each_entry(loop, &dentry->d_subdirs,
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d_u.d_child) {
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spin_lock(&loop->d_lock);
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dentry_lru_del(loop);
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spin_unlock(&loop->d_lock);
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__d_drop(loop);
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cond_resched_lock(&dcache_lock);
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}
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@ -892,6 +944,8 @@ resume:
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struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
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next = tmp->next;
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spin_lock(&dentry->d_lock);
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/*
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* move only zero ref count dentries to the end
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* of the unused list for prune_dcache
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@ -903,6 +957,8 @@ resume:
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dentry_lru_del(dentry);
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}
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spin_unlock(&dentry->d_lock);
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/*
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* We can return to the caller if we have found some (this
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* ensures forward progress). We'll be coming back to find
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