* [patch 1/3] vfs, dcache: Introduce lighten r/o rename_lock lockers
2011-07-14 22:35 [patch 0/3] A few preparation patches for dcache further dcache shrinker rework Cyrill Gorcunov
@ 2011-07-14 22:35 ` Cyrill Gorcunov
2011-07-14 22:35 ` [patch 2/3] vfs, dcache: Factor out rename_lock locking Cyrill Gorcunov
2011-07-14 22:35 ` [patch 3/3] vfs: Make the rename_lock per-sb Cyrill Gorcunov
2 siblings, 0 replies; 5+ messages in thread
From: Cyrill Gorcunov @ 2011-07-14 22:35 UTC (permalink / raw)
To: linux-fsdevel; +Cc: akpm, xemul, Cyrill Gorcunov
[-- Attachment #1: dcache-1-13.patch --]
[-- Type: text/plain, Size: 5647 bytes --]
From: Pavel Emelyanov <xemul@openvz.org>
Subject: [patch 1/3] vfs, dcache: Introduce lighten r/o rename_lock lockers
There are some places, that need to _lock_ the rename_lock, but they
do it for reading the dentry tree. When doing the write_seqlock they
force the existing "willing to restart" readers do the restart, which
is not actually required.
Introduce two more seqlock helpers, that lock the lock, but do not
update the seq count.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---
fs/dcache.c | 40 ++++++++++++++++++++--------------------
include/linux/seqlock.h | 16 ++++++++++++++++
2 files changed, 36 insertions(+), 20 deletions(-)
Index: linux-2.6.git/fs/dcache.c
===================================================================
--- linux-2.6.git.orig/fs/dcache.c
+++ linux-2.6.git/fs/dcache.c
@@ -1089,18 +1089,18 @@ resume:
if (!locked && read_seqretry(&rename_lock, seq))
goto rename_retry;
if (locked)
- write_sequnlock(&rename_lock);
+ read_sequnlock(&rename_lock);
return 0; /* No mount points found in tree */
positive:
if (!locked && read_seqretry(&rename_lock, seq))
goto rename_retry;
if (locked)
- write_sequnlock(&rename_lock);
+ read_sequnlock(&rename_lock);
return 1;
rename_retry:
locked = 1;
- write_seqlock(&rename_lock);
+ read_seqlock(&rename_lock);
goto again;
}
EXPORT_SYMBOL(have_submounts);
@@ -1191,14 +1191,14 @@ out:
if (!locked && read_seqretry(&rename_lock, seq))
goto rename_retry;
if (locked)
- write_sequnlock(&rename_lock);
+ read_sequnlock(&rename_lock);
return found;
rename_retry:
if (found)
return found;
locked = 1;
- write_seqlock(&rename_lock);
+ read_seqlock(&rename_lock);
goto again;
}
@@ -2562,9 +2562,9 @@ char *__d_path(const struct path *path,
int error;
prepend(&res, &buflen, "\0", 1);
- write_seqlock(&rename_lock);
+ read_seqlock(&rename_lock);
error = prepend_path(path, root, &res, &buflen);
- write_sequnlock(&rename_lock);
+ read_sequnlock(&rename_lock);
if (error)
return ERR_PTR(error);
@@ -2626,12 +2626,12 @@ char *d_path(const struct path *path, ch
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
get_fs_root(current->fs, &root);
- write_seqlock(&rename_lock);
+ read_seqlock(&rename_lock);
tmp = root;
error = path_with_deleted(path, &tmp, &res, &buflen);
if (error)
res = ERR_PTR(error);
- write_sequnlock(&rename_lock);
+ read_sequnlock(&rename_lock);
path_put(&root);
return res;
}
@@ -2657,12 +2657,12 @@ char *d_path_with_unreachable(const stru
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
get_fs_root(current->fs, &root);
- write_seqlock(&rename_lock);
+ read_seqlock(&rename_lock);
tmp = root;
error = path_with_deleted(path, &tmp, &res, &buflen);
if (!error && !path_equal(&tmp, &root))
error = prepend_unreachable(&res, &buflen);
- write_sequnlock(&rename_lock);
+ read_sequnlock(&rename_lock);
path_put(&root);
if (error)
res = ERR_PTR(error);
@@ -2729,9 +2729,9 @@ char *dentry_path_raw(struct dentry *den
{
char *retval;
- write_seqlock(&rename_lock);
+ read_seqlock(&rename_lock);
retval = __dentry_path(dentry, buf, buflen);
- write_sequnlock(&rename_lock);
+ read_sequnlock(&rename_lock);
return retval;
}
@@ -2742,7 +2742,7 @@ char *dentry_path(struct dentry *dentry,
char *p = NULL;
char *retval;
- write_seqlock(&rename_lock);
+ read_seqlock(&rename_lock);
if (d_unlinked(dentry)) {
p = buf + buflen;
if (prepend(&p, &buflen, "//deleted", 10) != 0)
@@ -2750,7 +2750,7 @@ char *dentry_path(struct dentry *dentry,
buflen++;
}
retval = __dentry_path(dentry, buf, buflen);
- write_sequnlock(&rename_lock);
+ read_sequnlock(&rename_lock);
if (!IS_ERR(retval) && p)
*p = '/'; /* restore '/' overriden with '\0' */
return retval;
@@ -2788,7 +2788,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, b
get_fs_root_and_pwd(current->fs, &root, &pwd);
error = -ENOENT;
- write_seqlock(&rename_lock);
+ read_seqlock(&rename_lock);
if (!d_unlinked(pwd.dentry)) {
unsigned long len;
struct path tmp = root;
@@ -2797,7 +2797,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, b
prepend(&cwd, &buflen, "\0", 1);
error = prepend_path(&pwd, &tmp, &cwd, &buflen);
- write_sequnlock(&rename_lock);
+ read_sequnlock(&rename_lock);
if (error)
goto out;
@@ -2817,7 +2817,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, b
error = -EFAULT;
}
} else {
- write_sequnlock(&rename_lock);
+ read_sequnlock(&rename_lock);
}
out:
@@ -2947,12 +2947,12 @@ resume:
if (!locked && read_seqretry(&rename_lock, seq))
goto rename_retry;
if (locked)
- write_sequnlock(&rename_lock);
+ read_sequnlock(&rename_lock);
return;
rename_retry:
locked = 1;
- write_seqlock(&rename_lock);
+ read_seqlock(&rename_lock);
goto again;
}
Index: linux-2.6.git/include/linux/seqlock.h
===================================================================
--- linux-2.6.git.orig/include/linux/seqlock.h
+++ linux-2.6.git/include/linux/seqlock.h
@@ -108,6 +108,22 @@ static __always_inline int read_seqretry
return unlikely(sl->sequence != start);
}
+/*
+ * Lock/unlock the critical section against updates but
+ * no sequence counter altering, so the other lockless
+ * readers will not have to restart reading data if
+ * read-only-lock occured.
+ */
+
+static __always_inline void read_seqlock(seqlock_t *sl)
+{
+ spin_lock(&sl->lock);
+}
+
+static __always_inline void read_sequnlock(seqlock_t *sl)
+{
+ spin_unlock(&sl->lock);
+}
/*
* Version using sequence counter only.
^ permalink raw reply [flat|nested] 5+ messages in thread* [patch 2/3] vfs, dcache: Factor out rename_lock locking
2011-07-14 22:35 [patch 0/3] A few preparation patches for dcache further dcache shrinker rework Cyrill Gorcunov
2011-07-14 22:35 ` [patch 1/3] vfs, dcache: Introduce lighten r/o rename_lock lockers Cyrill Gorcunov
@ 2011-07-14 22:35 ` Cyrill Gorcunov
2011-07-14 22:35 ` [patch 3/3] vfs: Make the rename_lock per-sb Cyrill Gorcunov
2 siblings, 0 replies; 5+ messages in thread
From: Cyrill Gorcunov @ 2011-07-14 22:35 UTC (permalink / raw)
To: linux-fsdevel; +Cc: akpm, xemul, Cyrill Gorcunov
[-- Attachment #1: dcache-2-13.patch --]
[-- Type: text/plain, Size: 4183 bytes --]
From: Pavel Emelyanov <xemul@openvz.org>
Subject: [patch 2/3] vfs, dcache: Factor out rename_lock locking
The set of routnes that try to get the dentry path with various
flavours end up in two "core" routines -- the prepend_path and
the __dentry_path.
Since the rename_lock only protects the path integrity, it's OK
to move the rename_lock locking inside these two.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---
fs/dcache.c | 27 ++++++---------------------
1 file changed, 6 insertions(+), 21 deletions(-)
Index: linux-2.6.git/fs/dcache.c
===================================================================
--- linux-2.6.git.orig/fs/dcache.c
+++ linux-2.6.git/fs/dcache.c
@@ -2489,6 +2489,7 @@ static int prepend_path(const struct pat
bool slash = false;
int error = 0;
+ read_seqlock(&rename_lock);
br_read_lock(vfsmount_lock);
while (dentry != root->dentry || vfsmnt != root->mnt) {
struct dentry * parent;
@@ -2521,6 +2522,7 @@ out:
error = prepend(buffer, buflen, "/", 1);
br_read_unlock(vfsmount_lock);
+ read_sequnlock(&rename_lock);
return error;
global_root:
@@ -2562,10 +2564,7 @@ char *__d_path(const struct path *path,
int error;
prepend(&res, &buflen, "\0", 1);
- read_seqlock(&rename_lock);
error = prepend_path(path, root, &res, &buflen);
- read_sequnlock(&rename_lock);
-
if (error)
return ERR_PTR(error);
return res;
@@ -2626,12 +2625,10 @@ char *d_path(const struct path *path, ch
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
get_fs_root(current->fs, &root);
- read_seqlock(&rename_lock);
tmp = root;
error = path_with_deleted(path, &tmp, &res, &buflen);
if (error)
res = ERR_PTR(error);
- read_sequnlock(&rename_lock);
path_put(&root);
return res;
}
@@ -2657,12 +2654,10 @@ char *d_path_with_unreachable(const stru
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
get_fs_root(current->fs, &root);
- read_seqlock(&rename_lock);
tmp = root;
error = path_with_deleted(path, &tmp, &res, &buflen);
if (!error && !path_equal(&tmp, &root))
error = prepend_unreachable(&res, &buflen);
- read_sequnlock(&rename_lock);
path_put(&root);
if (error)
res = ERR_PTR(error);
@@ -2706,6 +2701,7 @@ static char *__dentry_path(struct dentry
retval = end-1;
*retval = '/';
+ read_seqlock(&rename_lock);
while (!IS_ROOT(dentry)) {
struct dentry *parent = dentry->d_parent;
int error;
@@ -2720,20 +2716,16 @@ static char *__dentry_path(struct dentry
retval = end;
dentry = parent;
}
+ read_sequnlock(&rename_lock);
return retval;
Elong:
+ read_sequnlock(&rename_lock);
return ERR_PTR(-ENAMETOOLONG);
}
char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
{
- char *retval;
-
- read_seqlock(&rename_lock);
- retval = __dentry_path(dentry, buf, buflen);
- read_sequnlock(&rename_lock);
-
- return retval;
+ return __dentry_path(dentry, buf, buflen);
}
EXPORT_SYMBOL(dentry_path_raw);
@@ -2742,7 +2734,6 @@ char *dentry_path(struct dentry *dentry,
char *p = NULL;
char *retval;
- read_seqlock(&rename_lock);
if (d_unlinked(dentry)) {
p = buf + buflen;
if (prepend(&p, &buflen, "//deleted", 10) != 0)
@@ -2750,7 +2741,6 @@ char *dentry_path(struct dentry *dentry,
buflen++;
}
retval = __dentry_path(dentry, buf, buflen);
- read_sequnlock(&rename_lock);
if (!IS_ERR(retval) && p)
*p = '/'; /* restore '/' overriden with '\0' */
return retval;
@@ -2788,7 +2778,6 @@ SYSCALL_DEFINE2(getcwd, char __user *, b
get_fs_root_and_pwd(current->fs, &root, &pwd);
error = -ENOENT;
- read_seqlock(&rename_lock);
if (!d_unlinked(pwd.dentry)) {
unsigned long len;
struct path tmp = root;
@@ -2797,7 +2786,6 @@ SYSCALL_DEFINE2(getcwd, char __user *, b
prepend(&cwd, &buflen, "\0", 1);
error = prepend_path(&pwd, &tmp, &cwd, &buflen);
- read_sequnlock(&rename_lock);
if (error)
goto out;
@@ -2816,10 +2804,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, b
if (copy_to_user(buf, cwd, len))
error = -EFAULT;
}
- } else {
- read_sequnlock(&rename_lock);
}
-
out:
path_put(&pwd);
path_put(&root);
^ permalink raw reply [flat|nested] 5+ messages in thread* [patch 3/3] vfs: Make the rename_lock per-sb
2011-07-14 22:35 [patch 0/3] A few preparation patches for dcache further dcache shrinker rework Cyrill Gorcunov
2011-07-14 22:35 ` [patch 1/3] vfs, dcache: Introduce lighten r/o rename_lock lockers Cyrill Gorcunov
2011-07-14 22:35 ` [patch 2/3] vfs, dcache: Factor out rename_lock locking Cyrill Gorcunov
@ 2011-07-14 22:35 ` Cyrill Gorcunov
2 siblings, 0 replies; 5+ messages in thread
From: Cyrill Gorcunov @ 2011-07-14 22:35 UTC (permalink / raw)
To: linux-fsdevel; +Cc: akpm, xemul, Cyrill Gorcunov
[-- Attachment #1: dcache-3-13.patch --]
[-- Type: text/plain, Size: 12904 bytes --]
From: Pavel Emelyanov <xemul@openvz.org>
Subject: [patch 3/3] Make the rename_lock per-sb
There are two things I try to get with this patch.
The first one -- renames on different sb-s will not depend on each other.
The second one -- I plan to factor out the dcache shrinking code (in
further patches). In order to make the srink_dcache_for_umount work OK
on a dying SB it's better to have this lock non-global.
There's some trickery in the prepend_path -- this one has to relock
the rename lock as it ascends the vfsmount tree. This relock seems OK,
as the dentry path of each mount renames solid, and even if we "race"
with the rename on some of the super blocks, the overall path we get
will be either the one we had before rename or them one we had after
one, i.e. -- some existing one.
v2: Use a pointer s_rename_lock in nfs_path() instead of
dereferences in cycle.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---
drivers/staging/pohmelfs/path_entry.c | 4 +-
fs/autofs4/waitq.c | 6 +--
fs/dcache.c | 60 +++++++++++++++++-----------------
fs/nfs/namespace.c | 7 ++-
fs/super.c | 1
include/linux/dcache.h | 2 -
include/linux/fs.h | 2 +
kernel/auditsc.c | 4 +-
8 files changed, 44 insertions(+), 42 deletions(-)
Index: linux-2.6.git/drivers/staging/pohmelfs/path_entry.c
===================================================================
--- linux-2.6.git.orig/drivers/staging/pohmelfs/path_entry.c
+++ linux-2.6.git/drivers/staging/pohmelfs/path_entry.c
@@ -99,7 +99,7 @@ int pohmelfs_path_length(struct pohmelfs
rename_retry:
len = 1; /* Root slash */
d = first;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqbegin(&root->d_sb->s_rename_lock);
rcu_read_lock();
if (!IS_ROOT(d) && d_unhashed(d))
@@ -110,7 +110,7 @@ rename_retry:
d = d->d_parent;
}
rcu_read_unlock();
- if (read_seqretry(&rename_lock, seq))
+ if (read_seqretry(&root->d_sb->s_rename_lock, seq))
goto rename_retry;
dput(root);
Index: linux-2.6.git/fs/autofs4/waitq.c
===================================================================
--- linux-2.6.git.orig/fs/autofs4/waitq.c
+++ linux-2.6.git/fs/autofs4/waitq.c
@@ -195,7 +195,7 @@ rename_retry:
buf = *name;
len = 0;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqbegin(&sbi->sb->s_rename_lock);
rcu_read_lock();
spin_lock(&sbi->fs_lock);
for (tmp = dentry ; tmp != root ; tmp = tmp->d_parent)
@@ -204,7 +204,7 @@ rename_retry:
if (!len || --len > NAME_MAX) {
spin_unlock(&sbi->fs_lock);
rcu_read_unlock();
- if (read_seqretry(&rename_lock, seq))
+ if (read_seqretry(&sbi->sb->s_rename_lock, seq))
goto rename_retry;
return 0;
}
@@ -220,7 +220,7 @@ rename_retry:
}
spin_unlock(&sbi->fs_lock);
rcu_read_unlock();
- if (read_seqretry(&rename_lock, seq))
+ if (read_seqretry(&sbi->sb->s_rename_lock, seq))
goto rename_retry;
return len;
Index: linux-2.6.git/fs/dcache.c
===================================================================
--- linux-2.6.git.orig/fs/dcache.c
+++ linux-2.6.git/fs/dcache.c
@@ -80,10 +80,6 @@ int sysctl_vfs_cache_pressure __read_mos
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);
-
-EXPORT_SYMBOL(rename_lock);
-
static struct kmem_cache *dentry_cache __read_mostly;
/*
@@ -1014,7 +1010,7 @@ static struct dentry *try_to_ascend(stru
*/
if (new != old->d_parent ||
(old->d_flags & DCACHE_DISCONNECTED) ||
- (!locked && read_seqretry(&rename_lock, seq))) {
+ (!locked && read_seqretry(&old->d_sb->s_rename_lock, seq))) {
spin_unlock(&new->d_lock);
new = NULL;
}
@@ -1043,7 +1039,7 @@ int have_submounts(struct dentry *parent
unsigned seq;
int locked = 0;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqbegin(&parent->d_sb->s_rename_lock);
again:
this_parent = parent;
@@ -1086,21 +1082,21 @@ resume:
goto resume;
}
spin_unlock(&this_parent->d_lock);
- if (!locked && read_seqretry(&rename_lock, seq))
+ if (!locked && read_seqretry(&parent->d_sb->s_rename_lock, seq))
goto rename_retry;
if (locked)
- read_sequnlock(&rename_lock);
+ read_sequnlock(&parent->d_sb->s_rename_lock);
return 0; /* No mount points found in tree */
positive:
- if (!locked && read_seqretry(&rename_lock, seq))
+ if (!locked && read_seqretry(&parent->d_sb->s_rename_lock, seq))
goto rename_retry;
if (locked)
- read_sequnlock(&rename_lock);
+ read_sequnlock(&parent->d_sb->s_rename_lock);
return 1;
rename_retry:
locked = 1;
- read_seqlock(&rename_lock);
+ read_seqlock(&parent->d_sb->s_rename_lock);
goto again;
}
EXPORT_SYMBOL(have_submounts);
@@ -1127,7 +1123,7 @@ static int select_parent(struct dentry *
int found = 0;
int locked = 0;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqbegin(&parent->d_sb->s_rename_lock);
again:
this_parent = parent;
spin_lock(&this_parent->d_lock);
@@ -1188,17 +1184,17 @@ resume:
}
out:
spin_unlock(&this_parent->d_lock);
- if (!locked && read_seqretry(&rename_lock, seq))
+ if (!locked && read_seqretry(&parent->d_sb->s_rename_lock, seq))
goto rename_retry;
if (locked)
- read_sequnlock(&rename_lock);
+ read_sequnlock(&parent->d_sb->s_rename_lock);
return found;
rename_retry:
if (found)
return found;
locked = 1;
- read_seqlock(&rename_lock);
+ read_seqlock(&parent->d_sb->s_rename_lock);
goto again;
}
@@ -1861,11 +1857,11 @@ struct dentry *d_lookup(struct dentry *p
unsigned seq;
do {
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqbegin(&parent->d_sb->s_rename_lock);
dentry = __d_lookup(parent, name);
if (dentry)
break;
- } while (read_seqretry(&rename_lock, seq));
+ } while (read_seqretry(&parent->d_sb->s_rename_lock, seq));
return dentry;
}
EXPORT_SYMBOL(d_lookup);
@@ -2227,8 +2223,9 @@ void d_move(struct dentry * dentry, stru
BUG_ON(d_ancestor(dentry, target));
BUG_ON(d_ancestor(target, dentry));
+ BUG_ON(dentry->d_sb != target->d_sb);
- write_seqlock(&rename_lock);
+ write_seqlock(&dentry->d_sb->s_rename_lock);
dentry_lock_for_move(dentry, target);
@@ -2275,7 +2272,7 @@ void d_move(struct dentry * dentry, stru
spin_unlock(&target->d_lock);
fsnotify_d_move(dentry);
spin_unlock(&dentry->d_lock);
- write_sequnlock(&rename_lock);
+ write_sequnlock(&dentry->d_sb->s_rename_lock);
}
EXPORT_SYMBOL(d_move);
@@ -2489,8 +2486,8 @@ static int prepend_path(const struct pat
bool slash = false;
int error = 0;
- read_seqlock(&rename_lock);
br_read_lock(vfsmount_lock);
+ read_seqlock(&vfsmnt->mnt_sb->s_rename_lock);
while (dentry != root->dentry || vfsmnt != root->mnt) {
struct dentry * parent;
@@ -2500,7 +2497,9 @@ static int prepend_path(const struct pat
goto global_root;
}
dentry = vfsmnt->mnt_mountpoint;
+ read_sequnlock(&vfsmnt->mnt_sb->s_rename_lock);
vfsmnt = vfsmnt->mnt_parent;
+ read_seqlock(&vfsmnt->mnt_sb->s_rename_lock);
continue;
}
parent = dentry->d_parent;
@@ -2521,8 +2520,8 @@ out:
if (!error && !slash)
error = prepend(buffer, buflen, "/", 1);
+ read_sequnlock(&vfsmnt->mnt_sb->s_rename_lock);
br_read_unlock(vfsmount_lock);
- read_sequnlock(&rename_lock);
return error;
global_root:
@@ -2693,6 +2692,7 @@ static char *__dentry_path(struct dentry
{
char *end = buf + buflen;
char *retval;
+ struct super_block *sb = dentry->d_sb;
prepend(&end, &buflen, "\0", 1);
if (buflen < 1)
@@ -2701,7 +2701,7 @@ static char *__dentry_path(struct dentry
retval = end-1;
*retval = '/';
- read_seqlock(&rename_lock);
+ read_seqlock(&sb->s_rename_lock);
while (!IS_ROOT(dentry)) {
struct dentry *parent = dentry->d_parent;
int error;
@@ -2716,10 +2716,10 @@ static char *__dentry_path(struct dentry
retval = end;
dentry = parent;
}
- read_sequnlock(&rename_lock);
+ read_sequnlock(&sb->s_rename_lock);
return retval;
Elong:
- read_sequnlock(&rename_lock);
+ read_sequnlock(&sb->s_rename_lock);
return ERR_PTR(-ENAMETOOLONG);
}
@@ -2838,7 +2838,7 @@ int is_subdir(struct dentry *new_dentry,
do {
/* for restarting inner loop in case of seq retry */
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqbegin(&old_dentry->d_sb->s_rename_lock);
/*
* Need rcu_readlock to protect against the d_parent trashing
* due to d_move
@@ -2849,7 +2849,7 @@ int is_subdir(struct dentry *new_dentry,
else
result = 0;
rcu_read_unlock();
- } while (read_seqretry(&rename_lock, seq));
+ } while (read_seqretry(&old_dentry->d_sb->s_rename_lock, seq));
return result;
}
@@ -2886,7 +2886,7 @@ void d_genocide(struct dentry *root)
unsigned seq;
int locked = 0;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqbegin(&root->d_sb->s_rename_lock);
again:
this_parent = root;
spin_lock(&this_parent->d_lock);
@@ -2929,15 +2929,15 @@ resume:
goto resume;
}
spin_unlock(&this_parent->d_lock);
- if (!locked && read_seqretry(&rename_lock, seq))
+ if (!locked && read_seqretry(&root->d_sb->s_rename_lock, seq))
goto rename_retry;
if (locked)
- read_sequnlock(&rename_lock);
+ read_sequnlock(&root->d_sb->s_rename_lock);
return;
rename_retry:
locked = 1;
- read_seqlock(&rename_lock);
+ read_seqlock(&root->d_sb->s_rename_lock);
goto again;
}
Index: linux-2.6.git/fs/nfs/namespace.c
===================================================================
--- linux-2.6.git.orig/fs/nfs/namespace.c
+++ linux-2.6.git/fs/nfs/namespace.c
@@ -47,6 +47,7 @@ static struct vfsmount *nfs_do_submount(
*/
char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen)
{
+ seqlock_t *p_rename_lock = &dentry->d_sb->s_rename_lock;
char *end;
int namelen;
unsigned seq;
@@ -57,7 +58,7 @@ rename_retry:
*--end = '\0';
buflen--;
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqbegin(p_rename_lock);
rcu_read_lock();
while (1) {
spin_lock(&dentry->d_lock);
@@ -73,7 +74,7 @@ rename_retry:
spin_unlock(&dentry->d_lock);
dentry = dentry->d_parent;
}
- if (read_seqretry(&rename_lock, seq)) {
+ if (read_seqretry(p_rename_lock, seq)) {
spin_unlock(&dentry->d_lock);
rcu_read_unlock();
goto rename_retry;
@@ -112,7 +113,7 @@ rename_retry:
Elong_unlock:
spin_unlock(&dentry->d_lock);
rcu_read_unlock();
- if (read_seqretry(&rename_lock, seq))
+ if (read_seqretry(p_rename_lock, seq))
goto rename_retry;
Elong:
return ERR_PTR(-ENAMETOOLONG);
Index: linux-2.6.git/fs/super.c
===================================================================
--- linux-2.6.git.orig/fs/super.c
+++ linux-2.6.git/fs/super.c
@@ -105,6 +105,7 @@ static struct super_block *alloc_super(s
s->s_count = 1;
atomic_set(&s->s_active, 1);
mutex_init(&s->s_vfs_rename_mutex);
+ seqlock_init(&s->s_rename_lock);
lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
mutex_init(&s->s_dquot.dqio_mutex);
mutex_init(&s->s_dquot.dqonoff_mutex);
Index: linux-2.6.git/include/linux/dcache.h
===================================================================
--- linux-2.6.git.orig/include/linux/dcache.h
+++ linux-2.6.git/include/linux/dcache.h
@@ -219,8 +219,6 @@ struct dentry_operations {
#define DCACHE_MANAGED_DENTRY \
(DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
-extern seqlock_t rename_lock;
-
static inline int dname_external(struct dentry *dentry)
{
return dentry->d_name.name != dentry->d_iname;
Index: linux-2.6.git/include/linux/fs.h
===================================================================
--- linux-2.6.git.orig/include/linux/fs.h
+++ linux-2.6.git/include/linux/fs.h
@@ -1421,6 +1421,8 @@ struct super_block {
*/
struct mutex s_vfs_rename_mutex; /* Kludge */
+ seqlock_t s_rename_lock;
+
/*
* Filesystem subtype. If non-empty the filesystem type field
* in /proc/mounts will be "type.subtype"
Index: linux-2.6.git/kernel/auditsc.c
===================================================================
--- linux-2.6.git.orig/kernel/auditsc.c
+++ linux-2.6.git/kernel/auditsc.c
@@ -1779,7 +1779,7 @@ retry:
drop = NULL;
d = dentry;
rcu_read_lock();
- seq = read_seqbegin(&rename_lock);
+ seq = read_seqbegin(&dentry->d_sb->s_rename_lock);
for(;;) {
struct inode *inode = d->d_inode;
if (inode && unlikely(!hlist_empty(&inode->i_fsnotify_marks))) {
@@ -1797,7 +1797,7 @@ retry:
break;
d = parent;
}
- if (unlikely(read_seqretry(&rename_lock, seq) || drop)) { /* in this order */
+ if (unlikely(read_seqretry(&dentry->d_sb->s_rename_lock, seq) || drop)) { /* in this order */
rcu_read_unlock();
if (!drop) {
/* just a race with rename */
^ permalink raw reply [flat|nested] 5+ messages in thread
* [patch 2/3] vfs, dcache: Factor out rename_lock locking
2011-07-28 13:12 [patch 0/3] A few patches for dcache Cyrill Gorcunov
@ 2011-07-28 13:12 ` Cyrill Gorcunov
0 siblings, 0 replies; 5+ messages in thread
From: Cyrill Gorcunov @ 2011-07-28 13:12 UTC (permalink / raw)
To: Al Viro, LINUXFS-ML
Cc: Andrew Morton, Christoph Hellwig, James Bottomley, xemul,
Cyrill Gorcunov
[-- Attachment #1: dcache-2-13.patch --]
[-- Type: text/plain, Size: 4118 bytes --]
From: Pavel Emelyanov <xemul@openvz.org>
The set of routnes that try to get the dentry path with various
flavours end up in two "core" routines -- the prepend_path and
the __dentry_path.
Since the rename_lock only protects the path integrity, it's OK
to move the rename_lock locking inside these two.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
---
fs/dcache.c | 27 ++++++---------------------
1 file changed, 6 insertions(+), 21 deletions(-)
Index: linux-2.6.git/fs/dcache.c
===================================================================
--- linux-2.6.git.orig/fs/dcache.c
+++ linux-2.6.git/fs/dcache.c
@@ -2504,6 +2504,7 @@ static int prepend_path(const struct pat
bool slash = false;
int error = 0;
+ read_seqlock(&rename_lock);
br_read_lock(vfsmount_lock);
while (dentry != root->dentry || vfsmnt != root->mnt) {
struct dentry * parent;
@@ -2536,6 +2537,7 @@ out:
error = prepend(buffer, buflen, "/", 1);
br_read_unlock(vfsmount_lock);
+ read_sequnlock(&rename_lock);
return error;
global_root:
@@ -2577,10 +2579,7 @@ char *__d_path(const struct path *path,
int error;
prepend(&res, &buflen, "\0", 1);
- read_seqlock(&rename_lock);
error = prepend_path(path, root, &res, &buflen);
- read_sequnlock(&rename_lock);
-
if (error)
return ERR_PTR(error);
return res;
@@ -2641,12 +2640,10 @@ char *d_path(const struct path *path, ch
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
get_fs_root(current->fs, &root);
- read_seqlock(&rename_lock);
tmp = root;
error = path_with_deleted(path, &tmp, &res, &buflen);
if (error)
res = ERR_PTR(error);
- read_sequnlock(&rename_lock);
path_put(&root);
return res;
}
@@ -2672,12 +2669,10 @@ char *d_path_with_unreachable(const stru
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
get_fs_root(current->fs, &root);
- read_seqlock(&rename_lock);
tmp = root;
error = path_with_deleted(path, &tmp, &res, &buflen);
if (!error && !path_equal(&tmp, &root))
error = prepend_unreachable(&res, &buflen);
- read_sequnlock(&rename_lock);
path_put(&root);
if (error)
res = ERR_PTR(error);
@@ -2721,6 +2716,7 @@ static char *__dentry_path(struct dentry
retval = end-1;
*retval = '/';
+ read_seqlock(&rename_lock);
while (!IS_ROOT(dentry)) {
struct dentry *parent = dentry->d_parent;
int error;
@@ -2735,20 +2731,16 @@ static char *__dentry_path(struct dentry
retval = end;
dentry = parent;
}
+ read_sequnlock(&rename_lock);
return retval;
Elong:
+ read_sequnlock(&rename_lock);
return ERR_PTR(-ENAMETOOLONG);
}
char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
{
- char *retval;
-
- read_seqlock(&rename_lock);
- retval = __dentry_path(dentry, buf, buflen);
- read_sequnlock(&rename_lock);
-
- return retval;
+ return __dentry_path(dentry, buf, buflen);
}
EXPORT_SYMBOL(dentry_path_raw);
@@ -2757,7 +2749,6 @@ char *dentry_path(struct dentry *dentry,
char *p = NULL;
char *retval;
- read_seqlock(&rename_lock);
if (d_unlinked(dentry)) {
p = buf + buflen;
if (prepend(&p, &buflen, "//deleted", 10) != 0)
@@ -2765,7 +2756,6 @@ char *dentry_path(struct dentry *dentry,
buflen++;
}
retval = __dentry_path(dentry, buf, buflen);
- read_sequnlock(&rename_lock);
if (!IS_ERR(retval) && p)
*p = '/'; /* restore '/' overriden with '\0' */
return retval;
@@ -2803,7 +2793,6 @@ SYSCALL_DEFINE2(getcwd, char __user *, b
get_fs_root_and_pwd(current->fs, &root, &pwd);
error = -ENOENT;
- read_seqlock(&rename_lock);
if (!d_unlinked(pwd.dentry)) {
unsigned long len;
struct path tmp = root;
@@ -2812,7 +2801,6 @@ SYSCALL_DEFINE2(getcwd, char __user *, b
prepend(&cwd, &buflen, "\0", 1);
error = prepend_path(&pwd, &tmp, &cwd, &buflen);
- read_sequnlock(&rename_lock);
if (error)
goto out;
@@ -2831,10 +2819,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, b
if (copy_to_user(buf, cwd, len))
error = -EFAULT;
}
- } else {
- read_sequnlock(&rename_lock);
}
-
out:
path_put(&pwd);
path_put(&root);
^ permalink raw reply [flat|nested] 5+ messages in thread