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authorLinus Torvalds <torvalds@linux-foundation.org>2016-07-28 12:59:05 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-07-28 12:59:05 -0700
commit6784725ab0b9473ce44bfad91a256bd72b5cddc1 (patch)
treef31e2bfc4795c2ee490b0eb9fb752be58060568f /fs/dcache.c
parent554828ee0db41618d101d9549db8808af9fd9d65 (diff)
parent47be61845c775643f1aa4d2a54343549f943c94c (diff)
Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs updates from Al Viro: "Assorted cleanups and fixes. Probably the most interesting part long-term is ->d_init() - that will have a bunch of followups in (at least) ceph and lustre, but we'll need to sort the barrier-related rules before it can get used for really non-trivial stuff. Another fun thing is the merge of ->d_iput() callers (dentry_iput() and dentry_unlink_inode()) and a bunch of ->d_compare() ones (all except the one in __d_lookup_lru())" * 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (26 commits) fs/dcache.c: avoid soft-lockup in dput() vfs: new d_init method vfs: Update lookup_dcache() comment bdev: get rid of ->bd_inodes Remove last traces of ->sync_page new helper: d_same_name() dentry_cmp(): use lockless_dereference() instead of smp_read_barrier_depends() vfs: clean up documentation vfs: document ->d_real() vfs: merge .d_select_inode() into .d_real() unify dentry_iput() and dentry_unlink_inode() binfmt_misc: ->s_root is not going anywhere drop redundant ->owner initializations ufs: get rid of redundant checks orangefs: constify inode_operations missed comment updates from ->direct_IO() prototype change file_inode(f)->i_mapping is f->f_mapping trim fsnotify hooks a bit 9p: new helper - v9fs_parent_fid() debugfs: ->d_parent is never NULL or negative ...
Diffstat (limited to 'fs/dcache.c')
-rw-r--r--fs/dcache.c208
1 files changed, 69 insertions, 139 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 24bf27d66f6e..b90cf8e09d5b 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -224,10 +224,9 @@ static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char
static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
{
- const unsigned char *cs;
/*
* Be careful about RCU walk racing with rename:
- * use ACCESS_ONCE to fetch the name pointer.
+ * use 'lockless_dereference' to fetch the name pointer.
*
* NOTE! Even if a rename will mean that the length
* was not loaded atomically, we don't care. The
@@ -241,8 +240,8 @@ static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *c
* early because the data cannot match (there can
* be no NUL in the ct/tcount data)
*/
- cs = ACCESS_ONCE(dentry->d_name.name);
- smp_read_barrier_depends();
+ const unsigned char *cs = lockless_dereference(dentry->d_name.name);
+
return dentry_string_cmp(cs, ct, tcount);
}
@@ -333,44 +332,21 @@ static inline void dentry_rcuwalk_invalidate(struct dentry *dentry)
/*
* Release the dentry's inode, using the filesystem
- * d_iput() operation if defined. Dentry has no refcount
- * and is unhashed.
- */
-static void dentry_iput(struct dentry * dentry)
- __releases(dentry->d_lock)
- __releases(dentry->d_inode->i_lock)
-{
- struct inode *inode = dentry->d_inode;
- if (inode) {
- __d_clear_type_and_inode(dentry);
- hlist_del_init(&dentry->d_u.d_alias);
- spin_unlock(&dentry->d_lock);
- spin_unlock(&inode->i_lock);
- if (!inode->i_nlink)
- fsnotify_inoderemove(inode);
- if (dentry->d_op && dentry->d_op->d_iput)
- dentry->d_op->d_iput(dentry, inode);
- else
- iput(inode);
- } else {
- spin_unlock(&dentry->d_lock);
- }
-}
-
-/*
- * Release the dentry's inode, using the filesystem
- * d_iput() operation if defined. dentry remains in-use.
+ * d_iput() operation if defined.
*/
static void dentry_unlink_inode(struct dentry * dentry)
__releases(dentry->d_lock)
__releases(dentry->d_inode->i_lock)
{
struct inode *inode = dentry->d_inode;
+ bool hashed = !d_unhashed(dentry);
- raw_write_seqcount_begin(&dentry->d_seq);
+ if (hashed)
+ raw_write_seqcount_begin(&dentry->d_seq);
__d_clear_type_and_inode(dentry);
hlist_del_init(&dentry->d_u.d_alias);
- raw_write_seqcount_end(&dentry->d_seq);
+ if (hashed)
+ raw_write_seqcount_end(&dentry->d_seq);
spin_unlock(&dentry->d_lock);
spin_unlock(&inode->i_lock);
if (!inode->i_nlink)
@@ -571,12 +547,10 @@ static void __dentry_kill(struct dentry *dentry)
dentry_unlist(dentry, parent);
if (parent)
spin_unlock(&parent->d_lock);
- dentry_iput(dentry);
- /*
- * dentry_iput drops the locks, at which point nobody (except
- * transient RCU lookups) can reach this dentry.
- */
- BUG_ON(dentry->d_lockref.count > 0);
+ if (dentry->d_inode)
+ dentry_unlink_inode(dentry);
+ else
+ spin_unlock(&dentry->d_lock);
this_cpu_dec(nr_dentry);
if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry);
@@ -620,7 +594,6 @@ static struct dentry *dentry_kill(struct dentry *dentry)
failed:
spin_unlock(&dentry->d_lock);
- cpu_relax();
return dentry; /* try again with same dentry */
}
@@ -794,6 +767,8 @@ void dput(struct dentry *dentry)
return;
repeat:
+ might_sleep();
+
rcu_read_lock();
if (likely(fast_dput(dentry))) {
rcu_read_unlock();
@@ -827,8 +802,10 @@ repeat:
kill_it:
dentry = dentry_kill(dentry);
- if (dentry)
+ if (dentry) {
+ cond_resched();
goto repeat;
+ }
}
EXPORT_SYMBOL(dput);
@@ -1593,6 +1570,7 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
{
struct dentry *dentry;
char *dname;
+ int err;
dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
if (!dentry)
@@ -1651,6 +1629,16 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
INIT_LIST_HEAD(&dentry->d_child);
d_set_d_op(dentry, dentry->d_sb->s_d_op);
+ if (dentry->d_op && dentry->d_op->d_init) {
+ err = dentry->d_op->d_init(dentry);
+ if (err) {
+ if (dname_external(dentry))
+ kfree(external_name(dentry));
+ kmem_cache_free(dentry_cache, dentry);
+ return NULL;
+ }
+ }
+
this_cpu_inc(nr_dentry);
return dentry;
@@ -1727,7 +1715,6 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
DCACHE_OP_REVALIDATE |
DCACHE_OP_WEAK_REVALIDATE |
DCACHE_OP_DELETE |
- DCACHE_OP_SELECT_INODE |
DCACHE_OP_REAL));
dentry->d_op = op;
if (!op)
@@ -1744,8 +1731,6 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
dentry->d_flags |= DCACHE_OP_DELETE;
if (op->d_prune)
dentry->d_flags |= DCACHE_OP_PRUNE;
- if (op->d_select_inode)
- dentry->d_flags |= DCACHE_OP_SELECT_INODE;
if (op->d_real)
dentry->d_flags |= DCACHE_OP_REAL;
@@ -1813,7 +1798,7 @@ static void __d_instantiate(struct dentry *dentry, struct inode *inode)
raw_write_seqcount_begin(&dentry->d_seq);
__d_set_inode_and_type(dentry, inode, add_flags);
raw_write_seqcount_end(&dentry->d_seq);
- __fsnotify_d_instantiate(dentry);
+ fsnotify_update_flags(dentry);
spin_unlock(&dentry->d_lock);
}
@@ -2065,42 +2050,19 @@ struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
}
EXPORT_SYMBOL(d_add_ci);
-/*
- * Do the slow-case of the dentry name compare.
- *
- * Unlike the dentry_cmp() function, we need to atomically
- * load the name and length information, so that the
- * filesystem can rely on them, and can use the 'name' and
- * 'len' information without worrying about walking off the
- * end of memory etc.
- *
- * Thus the read_seqcount_retry() and the "duplicate" info
- * in arguments (the low-level filesystem should not look
- * at the dentry inode or name contents directly, since
- * rename can change them while we're in RCU mode).
- */
-enum slow_d_compare {
- D_COMP_OK,
- D_COMP_NOMATCH,
- D_COMP_SEQRETRY,
-};
-static noinline enum slow_d_compare slow_dentry_cmp(
- const struct dentry *parent,
- struct dentry *dentry,
- unsigned int seq,
- const struct qstr *name)
+static inline bool d_same_name(const struct dentry *dentry,
+ const struct dentry *parent,
+ const struct qstr *name)
{
- int tlen = dentry->d_name.len;
- const char *tname = dentry->d_name.name;
-
- if (read_seqcount_retry(&dentry->d_seq, seq)) {
- cpu_relax();
- return D_COMP_SEQRETRY;
+ if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
+ if (dentry->d_name.len != name->len)
+ return false;
+ return dentry_cmp(dentry, name->name, name->len) == 0;
}
- if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
- return D_COMP_NOMATCH;
- return D_COMP_OK;
+ return parent->d_op->d_compare(parent, dentry,
+ dentry->d_name.len, dentry->d_name.name,
+ name) == 0;
}
/**
@@ -2179,6 +2141,9 @@ seqretry:
* dentry compare, we will do seqretries until it is stable,
* and if we end up with a successful lookup, we actually
* want to exit RCU lookup anyway.
+ *
+ * Note that raw_seqcount_begin still *does* smp_rmb(), so
+ * we are still guaranteed NUL-termination of ->d_name.name.
*/
seq = raw_seqcount_begin(&dentry->d_seq);
if (dentry->d_parent != parent)
@@ -2187,24 +2152,28 @@ seqretry:
continue;
if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
+ int tlen;
+ const char *tname;
if (dentry->d_name.hash != hashlen_hash(hashlen))
continue;
- *seqp = seq;
- switch (slow_dentry_cmp(parent, dentry, seq, name)) {
- case D_COMP_OK:
- return dentry;
- case D_COMP_NOMATCH:
- continue;
- default:
+ tlen = dentry->d_name.len;
+ tname = dentry->d_name.name;
+ /* we want a consistent (name,len) pair */
+ if (read_seqcount_retry(&dentry->d_seq, seq)) {
+ cpu_relax();
goto seqretry;
}
+ if (parent->d_op->d_compare(parent, dentry,
+ tlen, tname, name) != 0)
+ continue;
+ } else {
+ if (dentry->d_name.hash_len != hashlen)
+ continue;
+ if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
+ continue;
}
-
- if (dentry->d_name.hash_len != hashlen)
- continue;
*seqp = seq;
- if (!dentry_cmp(dentry, str, hashlen_len(hashlen)))
- return dentry;
+ return dentry;
}
return NULL;
}
@@ -2252,9 +2221,7 @@ EXPORT_SYMBOL(d_lookup);
*/
struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
{
- unsigned int len = name->len;
unsigned int hash = name->hash;
- const unsigned char *str = name->name;
struct hlist_bl_head *b = d_hash(hash);
struct hlist_bl_node *node;
struct dentry *found = NULL;
@@ -2293,21 +2260,8 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
if (d_unhashed(dentry))
goto next;
- /*
- * It is safe to compare names since d_move() cannot
- * change the qstr (protected by d_lock).
- */
- if (parent->d_flags & DCACHE_OP_COMPARE) {
- int tlen = dentry->d_name.len;
- const char *tname = dentry->d_name.name;
- if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
- goto next;
- } else {
- if (dentry->d_name.len != len)
- goto next;
- if (dentry_cmp(dentry, str, len))
- goto next;
- }
+ if (!d_same_name(dentry, parent, name))
+ goto next;
dentry->d_lockref.count++;
found = dentry;
@@ -2460,9 +2414,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
const struct qstr *name,
wait_queue_head_t *wq)
{
- unsigned int len = name->len;
unsigned int hash = name->hash;
- const unsigned char *str = name->name;
struct hlist_bl_head *b = in_lookup_hash(parent, hash);
struct hlist_bl_node *node;
struct dentry *new = d_alloc(parent, name);
@@ -2513,17 +2465,8 @@ retry:
continue;
if (dentry->d_parent != parent)
continue;
- if (parent->d_flags & DCACHE_OP_COMPARE) {
- int tlen = dentry->d_name.len;
- const char *tname = dentry->d_name.name;
- if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
- continue;
- } else {
- if (dentry->d_name.len != len)
- continue;
- if (dentry_cmp(dentry, str, len))
- continue;
- }
+ if (!d_same_name(dentry, parent, name))
+ continue;
hlist_bl_unlock(b);
/* now we can try to grab a reference */
if (!lockref_get_not_dead(&dentry->d_lockref)) {
@@ -2550,17 +2493,8 @@ retry:
goto mismatch;
if (unlikely(d_unhashed(dentry)))
goto mismatch;
- if (parent->d_flags & DCACHE_OP_COMPARE) {
- int tlen = dentry->d_name.len;
- const char *tname = dentry->d_name.name;
- if (parent->d_op->d_compare(parent, dentry, tlen, tname, name))
- goto mismatch;
- } else {
- if (unlikely(dentry->d_name.len != len))
- goto mismatch;
- if (unlikely(dentry_cmp(dentry, str, len)))
- goto mismatch;
- }
+ if (unlikely(!d_same_name(dentry, parent, name)))
+ goto mismatch;
/* OK, it *is* a hashed match; return it */
spin_unlock(&dentry->d_lock);
dput(new);
@@ -2613,7 +2547,7 @@ static inline void __d_add(struct dentry *dentry, struct inode *inode)
raw_write_seqcount_begin(&dentry->d_seq);
__d_set_inode_and_type(dentry, inode, add_flags);
raw_write_seqcount_end(&dentry->d_seq);
- __fsnotify_d_instantiate(dentry);
+ fsnotify_update_flags(dentry);
}
_d_rehash(dentry);
if (dir)
@@ -2656,8 +2590,6 @@ EXPORT_SYMBOL(d_add);
struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
{
struct dentry *alias;
- int len = entry->d_name.len;
- const char *name = entry->d_name.name;
unsigned int hash = entry->d_name.hash;
spin_lock(&inode->i_lock);
@@ -2671,9 +2603,7 @@ struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
continue;
if (alias->d_parent != entry->d_parent)
continue;
- if (alias->d_name.len != len)
- continue;
- if (dentry_cmp(alias, name, len))
+ if (!d_same_name(alias, entry->d_parent, &entry->d_name))
continue;
spin_lock(&alias->d_lock);
if (!d_unhashed(alias)) {
@@ -2903,8 +2833,8 @@ static void __d_move(struct dentry *dentry, struct dentry *target,
list_move(&target->d_child, &target->d_parent->d_subdirs);
list_move(&dentry->d_child, &dentry->d_parent->d_subdirs);
if (exchange)
- fsnotify_d_move(target);
- fsnotify_d_move(dentry);
+ fsnotify_update_flags(target);
+ fsnotify_update_flags(dentry);
}
write_seqcount_end(&target->d_seq);