The d_path() and related kernel functions currently take a writer
lock on rename_lock because they need to follow pointers. By changing
rename_lock to be the new sequence read/write lock, a reader lock
can be taken and multiple d_path() threads can proceed concurrently
without blocking each other.
It is unlikely that the frequency of filesystem changes and d_path()
name lookup will be high enough to cause writer starvation, the current
limitation of the read/write lock should be acceptable in that case.
All the sites where rename_lock is referenced were modified to use the
sequence read/write lock declaration and access functions.
When apply this patch to 3.8 or earlier releases, the unused function
d_path_with_unreachable() in fs/dcache.c should be removed to avoid
compilation warning.
Signed-off-by: Waiman Long <Waiman.Long@xxxxxx>
---
fs/autofs4/waitq.c | 6 ++--
fs/ceph/mds_client.c | 4 +-
fs/cifs/dir.c | 4 +-
fs/dcache.c | 83 ++++++++++++++++++++++++-----------------------
fs/nfs/namespace.c | 6 ++--
include/linux/dcache.h | 4 +-
kernel/auditsc.c | 4 +-
7 files changed, 56 insertions(+), 55 deletions(-)
diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
index 3db70da..3afc4db 100644
--- a/fs/autofs4/waitq.c
+++ b/fs/autofs4/waitq.c
@@ -197,7 +197,7 @@ rename_retry:
buf = *name;
len = 0;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqrwbegin(&rename_lock);
rcu_read_lock();
spin_lock(&sbi->fs_lock);
for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
@@ -206,7 +206,7 @@ rename_retry:
if (!len || --len > NAME_MAX) {
spin_unlock(&sbi->fs_lock);
rcu_read_unlock();
- if (read_seqretry(&rename_lock, seq))
+ if (read_seqrwretry(&rename_lock, seq))
goto rename_retry;
return 0;
}
@@ -222,7 +222,7 @@ rename_retry:
}
spin_unlock(&sbi->fs_lock);
rcu_read_unlock();
- if (read_seqretry(&rename_lock, seq))
+ if (read_seqrwretry(&rename_lock, seq))
goto rename_retry;
return len;
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 442880d..da565c4 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -1486,7 +1486,7 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *base,
retry:
len = 0;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqrwbegin(&rename_lock);
rcu_read_lock();
for (temp = dentry; !IS_ROOT(temp);) {
struct inode *inode = temp->d_inode;
@@ -1536,7 +1536,7 @@ retry:
temp = temp->d_parent;
}
rcu_read_unlock();
- if (pos != 0 || read_seqretry(&rename_lock, seq)) {
+ if (pos != 0 || read_seqrwretry(&rename_lock, seq)) {
pr_err("build_path did not end path lookup where "
"expected, namelen is %d, pos is %d\n", len, pos);
/* presumably this is only possible if racing with a
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 1cd0162..707d849 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -96,7 +96,7 @@ build_path_from_dentry(struct dentry *direntry)
dfsplen = 0;
cifs_bp_rename_retry:
namelen = dfsplen;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqrwbegin(&rename_lock);
rcu_read_lock();
for (temp = direntry; !IS_ROOT(temp);) {
namelen += (1 + temp->d_name.len);
@@ -136,7 +136,7 @@ cifs_bp_rename_retry:
}
}
rcu_read_unlock();
- if (namelen != dfsplen || read_seqretry(&rename_lock, seq)) {
+ if (namelen != dfsplen || read_seqrwretry(&rename_lock, seq)) {
cFYI(1, "did not end path lookup where expected. namelen=%d "
"dfsplen=%d", namelen, dfsplen);
/* presumably this is only possible if racing with a rename
diff --git a/fs/dcache.c b/fs/dcache.c
index 48c0680..9477d80 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -29,6 +29,7 @@
#include <asm/uaccess.h>
#include <linux/security.h>
#include <linux/seqlock.h>
+#include <linux/seqrwlock.h>
#include <linux/swap.h>
#include <linux/bootmem.h>
#include <linux/fs_struct.h>
@@ -82,7 +83,7 @@ int sysctl_vfs_cache_pressure __read_mostly = 100;
EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
-__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
+__cacheline_aligned_in_smp DEFINE_SEQRWLOCK(rename_lock);
EXPORT_SYMBOL(rename_lock);
@@ -1020,7 +1021,7 @@ static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq
*/
if (new != old->d_parent ||
(old->d_flags & DCACHE_DENTRY_KILLED) ||
- (!locked && read_seqretry(&rename_lock, seq))) {
+ (!locked && read_seqrwretry(&rename_lock, seq))) {
spin_unlock(&new->d_lock);
new = NULL;
}
@@ -1049,7 +1050,7 @@ int have_submounts(struct dentry *parent)
unsigned seq;
int locked = 0;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqrwbegin(&rename_lock);
again:
this_parent = parent;
@@ -1092,23 +1093,23 @@ resume:
goto resume;
}
spin_unlock(&this_parent->d_lock);
- if (!locked && read_seqretry(&rename_lock, seq))
+ if (!locked && read_seqrwretry(&rename_lock, seq))
goto rename_retry;
if (locked)
- write_sequnlock(&rename_lock);
+ write_seqrwunlock(&rename_lock);
return 0; /* No mount points found in tree */
positive:
- if (!locked && read_seqretry(&rename_lock, seq))
+ if (!locked && read_seqrwretry(&rename_lock, seq))
goto rename_retry;
if (locked)
- write_sequnlock(&rename_lock);
+ write_seqrwunlock(&rename_lock);
return 1;
rename_retry:
if (locked)
goto again;
locked = 1;
- write_seqlock(&rename_lock);
+ write_seqrwlock(&rename_lock);
goto again;
}
EXPORT_SYMBOL(have_submounts);
@@ -1135,7 +1136,7 @@ static int select_parent(struct dentry *parent, struct list_head *dispose)
int found = 0;
int locked = 0;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqrwbegin(&rename_lock);
again:
this_parent = parent;
spin_lock(&this_parent->d_lock);
@@ -1200,10 +1201,10 @@ resume:
}
out:
spin_unlock(&this_parent->d_lock);
- if (!locked && read_seqretry(&rename_lock, seq))
+ if (!locked && read_seqrwretry(&rename_lock, seq))
goto rename_retry;
if (locked)
- write_sequnlock(&rename_lock);
+ write_seqrwunlock(&rename_lock);
return found;
rename_retry:
@@ -1212,7 +1213,7 @@ rename_retry:
if (locked)
goto again;
locked = 1;
- write_seqlock(&rename_lock);
+ write_seqrwlock(&rename_lock);
goto again;
}
@@ -1825,7 +1826,7 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
* It is possible that concurrent renames can mess up our list
* walk here and result in missing our dentry, resulting in the
* false-negative result. d_lookup() protects against concurrent
- * renames using rename_lock seqlock.
+ * renames using rename_lock seqrwlock.
*
* See Documentation/filesystems/path-lookup.txt for more details.
*/
@@ -1893,11 +1894,11 @@ struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
unsigned seq;
do {
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqrwbegin(&rename_lock);
dentry = __d_lookup(parent, name);
if (dentry)
break;
- } while (read_seqretry(&rename_lock, seq));
+ } while (read_seqrwretry(&rename_lock, seq));
return dentry;
}
EXPORT_SYMBOL(d_lookup);
@@ -1911,7 +1912,7 @@ EXPORT_SYMBOL(d_lookup);
* __d_lookup is like d_lookup, however it may (rarely) return a
* false-negative result due to unrelated rename activity.
*
- * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
+ * __d_lookup is slightly faster by avoiding rename_lock read seqrwlock,
* however it must be used carefully, eg. with a following d_lookup in
* the case of failure.
*
@@ -1943,7 +1944,7 @@ struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
* It is possible that concurrent renames can mess up our list
* walk here and result in missing our dentry, resulting in the
* false-negative result. d_lookup() protects against concurrent
- * renames using rename_lock seqlock.
+ * renames using rename_lock seqrwlock.
*
* See Documentation/filesystems/path-lookup.txt for more details.
*/
@@ -2318,9 +2319,9 @@ static void __d_move(struct dentry * dentry, struct dentry * target)
*/
void d_move(struct dentry *dentry, struct dentry *target)
{
- write_seqlock(&rename_lock);
+ write_seqrwlock(&rename_lock);
__d_move(dentry, target);
- write_sequnlock(&rename_lock);
+ write_seqrwunlock(&rename_lock);
}
EXPORT_SYMBOL(d_move);
@@ -2449,7 +2450,7 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
alias = __d_find_alias(inode, 0);
if (alias) {
actual = alias;
- write_seqlock(&rename_lock);
+ write_seqrwlock(&rename_lock);
if (d_ancestor(alias, dentry)) {
/* Check for loops */
@@ -2459,7 +2460,7 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
/* Is this an anonymous mountpoint that we
* could splice into our tree? */
__d_materialise_dentry(dentry, alias);
- write_sequnlock(&rename_lock);
+ write_seqrwunlock(&rename_lock);
__d_drop(alias);
goto found;
} else {
@@ -2467,7 +2468,7 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
* aliasing. This drops inode->i_lock */
actual = __d_unalias(inode, dentry, alias);
}
- write_sequnlock(&rename_lock);
+ write_seqrwunlock(&rename_lock);
if (IS_ERR(actual)) {
if (PTR_ERR(actual) == -ELOOP)
pr_warn_ratelimited(
@@ -2614,9 +2615,9 @@ char *__d_path(const struct path *path,
int error;
prepend(&res, &buflen, "\0", 1);
- write_seqlock(&rename_lock);
+ read_seqrwlock(&rename_lock);
error = prepend_path(path, root, &res, &buflen);
- write_sequnlock(&rename_lock);
+ read_seqrwunlock(&rename_lock);
if (error < 0)
return ERR_PTR(error);
@@ -2633,9 +2634,9 @@ char *d_absolute_path(const struct path *path,
int error;
prepend(&res, &buflen, "\0", 1);
- write_seqlock(&rename_lock);
+ read_seqrwlock(&rename_lock);
error = prepend_path(path, &root, &res, &buflen);
- write_sequnlock(&rename_lock);
+ read_seqrwunlock(&rename_lock);
if (error > 1)
error = -EINVAL;
@@ -2699,11 +2700,11 @@ char *d_path(const struct path *path, char *buf, int buflen)
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
get_fs_root(current->fs, &root);
- write_seqlock(&rename_lock);
+ read_seqrwlock(&rename_lock);
error = path_with_deleted(path, &root, &res, &buflen);
if (error < 0)
res = ERR_PTR(error);
- write_sequnlock(&rename_lock);
+ read_seqrwunlock(&rename_lock);
path_put(&root);
return res;
}
@@ -2768,9 +2769,9 @@ char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
{
char *retval;
- write_seqlock(&rename_lock);
+ read_seqrwlock(&rename_lock);
retval = __dentry_path(dentry, buf, buflen);
- write_sequnlock(&rename_lock);
+ read_seqrwunlock(&rename_lock);
return retval;
}
@@ -2781,7 +2782,7 @@ char *dentry_path(struct dentry *dentry, char *buf, int buflen)
char *p = NULL;
char *retval;
- write_seqlock(&rename_lock);
+ read_seqrwlock(&rename_lock);
if (d_unlinked(dentry)) {
p = buf + buflen;
if (prepend(&p, &buflen, "//deleted", 10) != 0)
@@ -2789,7 +2790,7 @@ char *dentry_path(struct dentry *dentry, char *buf, int buflen)
buflen++;
}
retval = __dentry_path(dentry, buf, buflen);
- write_sequnlock(&rename_lock);
+ read_seqrwunlock(&rename_lock);
if (!IS_ERR(retval) && p)
*p = '/'; /* restore '/' overriden with '\0' */
return retval;
@@ -2827,7 +2828,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
get_fs_root_and_pwd(current->fs, &root, &pwd);
error = -ENOENT;
- write_seqlock(&rename_lock);
+ read_seqrwlock(&rename_lock);
if (!d_unlinked(pwd.dentry)) {
unsigned long len;
char *cwd = page + PAGE_SIZE;
@@ -2835,7 +2836,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
prepend(&cwd, &buflen, "\0", 1);
error = prepend_path(&pwd, &root, &cwd, &buflen);
- write_sequnlock(&rename_lock);
+ read_seqrwunlock(&rename_lock);
if (error < 0)
goto out;
@@ -2855,7 +2856,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
error = -EFAULT;
}
} else {
- write_sequnlock(&rename_lock);
+ read_seqrwunlock(&rename_lock);
}
out:
@@ -2891,7 +2892,7 @@ int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
do {
/* for restarting inner loop in case of seq retry */
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqrwbegin(&rename_lock);
/*
* Need rcu_readlock to protect against the d_parent trashing
* due to d_move
@@ -2902,7 +2903,7 @@ int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
else
result = 0;
rcu_read_unlock();
- } while (read_seqretry(&rename_lock, seq));
+ } while (read_seqrwretry(&rename_lock, seq));
return result;
}
@@ -2914,7 +2915,7 @@ void d_genocide(struct dentry *root)
unsigned seq;
int locked = 0;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqrwbegin(&rename_lock);
again:
this_parent = root;
spin_lock(&this_parent->d_lock);
@@ -2957,17 +2958,17 @@ resume:
goto resume;
}
spin_unlock(&this_parent->d_lock);
- if (!locked && read_seqretry(&rename_lock, seq))
+ if (!locked && read_seqrwretry(&rename_lock, seq))
goto rename_retry;
if (locked)
- write_sequnlock(&rename_lock);
+ write_seqrwunlock(&rename_lock);
return;
rename_retry:
if (locked)
goto again;
locked = 1;
- write_seqlock(&rename_lock);
+ write_seqrwlock(&rename_lock);
goto again;
}
diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index fc8dc20..0eca871 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -60,7 +60,7 @@ rename_retry:
*--end = '\0';
buflen--;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqrwbegin(&rename_lock);
rcu_read_lock();
while (1) {
spin_lock(&dentry->d_lock);
@@ -76,7 +76,7 @@ rename_retry:
spin_unlock(&dentry->d_lock);
dentry = dentry->d_parent;
}
- if (read_seqretry(&rename_lock, seq)) {
+ if (read_seqrwretry(&rename_lock, seq)) {
spin_unlock(&dentry->d_lock);
rcu_read_unlock();
goto rename_retry;
@@ -117,7 +117,7 @@ rename_retry:
Elong_unlock:
spin_unlock(&dentry->d_lock);
rcu_read_unlock();
- if (read_seqretry(&rename_lock, seq))
+ if (read_seqrwretry(&rename_lock, seq))
goto rename_retry;
Elong:
return ERR_PTR(-ENAMETOOLONG);
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 99da5e2..5f05815 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -6,7 +6,7 @@
#include <linux/rculist.h>
#include <linux/rculist_bl.h>
#include <linux/spinlock.h>
-#include <linux/seqlock.h>
+#include <linux/seqrwlock.h>
#include <linux/cache.h>
#include <linux/rcupdate.h>
@@ -210,7 +210,7 @@ struct dentry_operations {
#define DCACHE_DENTRY_KILLED 0x100000
-extern seqlock_t rename_lock;
+extern seqrwlock_t rename_lock;
static inline int dname_external(struct dentry *dentry)
{
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index a371f85..767421e 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1892,7 +1892,7 @@ retry:
drop = NULL;
d = dentry;
rcu_read_lock();
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqrwbegin(&rename_lock);
for(;;) {
struct inode *inode = d->d_inode;
if (inode && unlikely(!hlist_empty(&inode->i_fsnotify_marks))) {
@@ -1910,7 +1910,7 @@ retry:
break;
d = parent;
}
- if (unlikely(read_seqretry(&rename_lock, seq) || drop)) { /* in this order */
+ if (unlikely(read_seqrwretry(&rename_lock, seq) || drop)) { /* in this order */
rcu_read_unlock();
if (!drop) {
/* just a race with rename */
--
1.7.1
--
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