[patch 13/52] fs: dcache scale d_unhashed

From: npiggin
Date: Wed Jun 23 2010 - 23:20:37 EST

Protect d_unhashed(dentry) condition with d_lock.

Signed-off-by: Nick Piggin <npiggin@xxxxxxx>
---
arch/powerpc/platforms/cell/spufs/inode.c | 3 +
fs/configfs/configfs_internal.h | 2 +
fs/dcache.c | 58 ++++++++++++++++++++++++------
fs/libfs.c | 29 ++++++++++-----
fs/ocfs2/dcache.c | 5 ++
fs/seq_file.c | 3 +
security/tomoyo/realpath.c | 2 +
7 files changed, 81 insertions(+), 21 deletions(-)

Index: linux-2.6/fs/libfs.c
===================================================================
--- linux-2.6.orig/fs/libfs.c
+++ linux-2.6/fs/libfs.c
@@ -16,6 +16,11 @@

#include <asm/uaccess.h>

+static inline int simple_positive(struct dentry *dentry)
+{
+ return dentry->d_inode && !d_unhashed(dentry);
+}
+
int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
struct kstat *stat)
{
@@ -100,8 +105,10 @@ loff_t dcache_dir_lseek(struct file *fil
while (n && p != &file->f_path.dentry->d_subdirs) {
struct dentry *next;
next = list_entry(p, struct dentry, d_u.d_child);
- if (!d_unhashed(next) && next->d_inode)
+ spin_lock(&next->d_lock);
+ if (simple_positive(next))
n--;
+ spin_unlock(&next->d_lock);
p = p->next;
}
list_add_tail(&cursor->d_u.d_child, p);
@@ -155,9 +162,13 @@ int dcache_readdir(struct file * filp, v
for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
struct dentry *next;
next = list_entry(p, struct dentry, d_u.d_child);
- if (d_unhashed(next) || !next->d_inode)
+ spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
+ if (!simple_positive(next)) {
+ spin_unlock(&next->d_lock);
continue;
+ }

+ spin_unlock(&next->d_lock);
spin_unlock(&dcache_lock);
if (filldir(dirent, next->d_name.name,
next->d_name.len, filp->f_pos,
@@ -262,20 +273,20 @@ int simple_link(struct dentry *old_dentr
return 0;
}

-static inline int simple_positive(struct dentry *dentry)
-{
- return dentry->d_inode && !d_unhashed(dentry);
-}
-
int simple_empty(struct dentry *dentry)
{
struct dentry *child;
int ret = 0;

spin_lock(&dcache_lock);
- list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
- if (simple_positive(child))
+ list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) {
+ spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
+ if (simple_positive(child)) {
+ spin_unlock(&child->d_lock);
goto out;
+ }
+ spin_unlock(&child->d_lock);
+ }
ret = 1;
out:
spin_unlock(&dcache_lock);
Index: linux-2.6/fs/seq_file.c
===================================================================
--- linux-2.6.orig/fs/seq_file.c
+++ linux-2.6/fs/seq_file.c
@@ -6,10 +6,13 @@
*/

#include <linux/fs.h>
+#include <linux/mount.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/slab.h>

+#include "internal.h"
+
#include <asm/uaccess.h>
#include <asm/page.h>

@@ -463,7 +466,9 @@ int seq_path_root(struct seq_file *m, st
char *p;

spin_lock(&dcache_lock);
+ br_read_lock(vfsmount_lock);
p = __d_path(path, root, buf, size);
+ br_read_unlock(vfsmount_lock);
spin_unlock(&dcache_lock);
res = PTR_ERR(p);
if (!IS_ERR(p)) {
Index: linux-2.6/fs/dcache.c
===================================================================
--- linux-2.6.orig/fs/dcache.c
+++ linux-2.6/fs/dcache.c
@@ -46,6 +46,7 @@
* - d_name
* - d_lru
* - d_count
+ * - d_unhashed()
*
* Ordering:
* dcache_lock
@@ -53,6 +54,13 @@
* dcache_lru_lock
* dcache_hash_lock
*
+ * If there is an ancestor relationship:
+ * dentry->d_parent->...->d_parent->d_lock
+ * ...
+ * dentry->d_parent->d_lock
+ * dentry->d_lock
+ *
+ * If no ancestor relationship:
* if (dentry1 < dentry2)
* dentry1->d_lock
* dentry2->d_lock
@@ -334,7 +342,9 @@ int d_invalidate(struct dentry * dentry)
* If it's already been dropped, return OK.
*/
spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
if (d_unhashed(dentry)) {
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
return 0;
}
@@ -343,9 +353,11 @@ int d_invalidate(struct dentry * dentry)
* to get rid of unused child entries.
*/
if (!list_empty(&dentry->d_subdirs)) {
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
shrink_dcache_parent(dentry);
spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
}

/*
@@ -358,7 +370,6 @@ int d_invalidate(struct dentry * dentry)
* we might still populate it if it was a
* working directory or similar).
*/
- spin_lock(&dentry->d_lock);
if (dentry->d_count > 1) {
if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
spin_unlock(&dentry->d_lock);
@@ -457,15 +468,18 @@ static struct dentry * __d_find_alias(st
next = tmp->next;
prefetch(next);
alias = list_entry(tmp, struct dentry, d_alias);
+ spin_lock(&alias->d_lock);
if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
if (IS_ROOT(alias) &&
(alias->d_flags & DCACHE_DISCONNECTED))
discon_alias = alias;
else if (!want_discon) {
- __dget_locked(alias);
+ __dget_locked_dlock(alias);
+ spin_unlock(&alias->d_lock);
return alias;
}
}
+ spin_unlock(&alias->d_lock);
}
if (discon_alias)
__dget_locked(discon_alias);
@@ -750,8 +764,8 @@ static void shrink_dcache_for_umount_sub
spin_lock(&dcache_lock);
spin_lock(&dentry->d_lock);
dentry_lru_del_init(dentry);
- spin_unlock(&dentry->d_lock);
__d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);

for (;;) {
@@ -766,8 +780,8 @@ static void shrink_dcache_for_umount_sub
d_u.d_child) {
spin_lock(&loop->d_lock);
dentry_lru_del_init(loop);
- spin_unlock(&loop->d_lock);
__d_drop(loop);
+ spin_unlock(&loop->d_lock);
cond_resched_lock(&dcache_lock);
}
spin_unlock(&dcache_lock);
@@ -1788,7 +1802,10 @@ static void d_move_locked(struct dentry
/*
* XXXX: do we really need to take target->d_lock?
*/
- if (target < dentry) {
+ if (d_ancestor(dentry, target)) {
+ spin_lock(&dentry->d_lock);
+ spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
+ } else if (d_ancestor(target, dentry) || target < dentry) {
spin_lock(&target->d_lock);
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
} else {
@@ -2046,7 +2063,8 @@ static int prepend_name(char **buffer, i
* Returns a pointer into the buffer or an error code if the
* path was too long.
*
- * "buflen" should be positive. Caller holds the dcache_lock.
+ * "buflen" should be positive. Caller holds the dcache_lock and
+ * path->dentry->d_lock.
*
* If path is not reachable from the supplied root, then the value of
* root is changed (without modifying refcounts).
@@ -2059,8 +2077,9 @@ char *__d_path(const struct path *path,
char *end = buffer + buflen;
char *retval;

- br_read_lock(vfsmount_lock);
prepend(&end, &buflen, "\0", 1);
+ spin_lock(&dentry->d_lock);
+unlinked:
if (d_unlinked(dentry) &&
(prepend(&end, &buflen, " (deleted)", 10) != 0))
goto Elong;
@@ -2072,7 +2091,7 @@ char *__d_path(const struct path *path,
*retval = '/';

for (;;) {
- struct dentry * parent;
+ struct dentry *parent;

if (dentry == root->dentry && vfsmnt == root->mnt)
break;
@@ -2081,8 +2100,10 @@ char *__d_path(const struct path *path,
if (vfsmnt->mnt_parent == vfsmnt) {
goto global_root;
}
+ spin_unlock(&dentry->d_lock);
dentry = vfsmnt->mnt_mountpoint;
vfsmnt = vfsmnt->mnt_parent;
+ spin_lock(&dentry->d_lock); /* can't get unlinked because locked vfsmount */
continue;
}
parent = dentry->d_parent;
@@ -2091,11 +2112,14 @@ char *__d_path(const struct path *path,
(prepend(&end, &buflen, "/", 1) != 0))
goto Elong;
retval = end;
+ spin_unlock(&dentry->d_lock);
dentry = parent;
+ if (d_unlinked(dentry))
+ goto unlinked;
}

out:
- br_read_unlock(vfsmount_lock);
+ spin_unlock(&dentry->d_lock);
return retval;

global_root:
@@ -2147,10 +2171,14 @@ char *d_path(const struct path *path, ch
root = current->fs->root;
path_get(&root);
spin_unlock(&current->fs->lock);
+
spin_lock(&dcache_lock);
+ br_read_lock(vfsmount_lock);
tmp = root;
res = __d_path(path, &tmp, buf, buflen);
+ br_read_unlock(vfsmount_lock);
spin_unlock(&dcache_lock);
+
path_put(&root);
return res;
}
@@ -2186,7 +2214,9 @@ char *dentry_path(struct dentry *dentry,
char *retval;

spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
prepend(&end, &buflen, "\0", 1);
+unlinked:
if (d_unlinked(dentry) &&
(prepend(&end, &buflen, "//deleted", 9) != 0))
goto Elong;
@@ -2205,11 +2235,17 @@ char *dentry_path(struct dentry *dentry,
goto Elong;

retval = end;
+ spin_unlock(&dentry->d_lock);
dentry = parent;
+ spin_lock(&dentry->d_lock);
+ if (d_unlinked(dentry))
+ goto unlinked;
}
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
return retval;
Elong:
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
return ERR_PTR(-ENAMETOOLONG);
}
@@ -2250,12 +2286,17 @@ SYSCALL_DEFINE2(getcwd, char __user *, b

error = -ENOENT;
spin_lock(&dcache_lock);
+ br_read_lock(vfsmount_lock);
+ spin_lock(&pwd.dentry->d_lock);
if (!d_unlinked(pwd.dentry)) {
unsigned long len;
struct path tmp = root;
char * cwd;

+ spin_unlock(&pwd.dentry->d_lock);
+ /* XXX: race here, have to close (eg. return unlinked from __d_path) */
cwd = __d_path(&pwd, &tmp, page, PAGE_SIZE);
+ br_read_unlock(vfsmount_lock);
spin_unlock(&dcache_lock);

error = PTR_ERR(cwd);
@@ -2269,8 +2310,11 @@ SYSCALL_DEFINE2(getcwd, char __user *, b
if (copy_to_user(buf, cwd, len))
error = -EFAULT;
}
- } else
+ } else {
+ spin_unlock(&pwd.dentry->d_lock);
+ br_read_unlock(vfsmount_lock);
spin_unlock(&dcache_lock);
+ }

out:
path_put(&pwd);
@@ -2359,13 +2403,16 @@ resume:
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
next = tmp->next;
- if (d_unhashed(dentry)||!dentry->d_inode)
+ spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+ if (d_unhashed(dentry) || !dentry->d_inode) {
+ spin_unlock(&dentry->d_lock);
continue;
+ }
if (!list_empty(&dentry->d_subdirs)) {
+ spin_unlock(&dentry->d_lock);
this_parent = dentry;
goto repeat;
}
- spin_lock(&dentry->d_lock);
dentry->d_count--;
spin_unlock(&dentry->d_lock);
}
Index: linux-2.6/arch/powerpc/platforms/cell/spufs/inode.c
===================================================================
--- linux-2.6.orig/arch/powerpc/platforms/cell/spufs/inode.c
+++ linux-2.6/arch/powerpc/platforms/cell/spufs/inode.c
@@ -165,6 +165,9 @@ static void spufs_prune_dir(struct dentr
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
simple_unlink(dir->d_inode, dentry);
+ /* XXX: what is dcache_lock protecting here? Other
+ * filesystems (IB, configfs) release dcache_lock
+ * before unlink */
spin_unlock(&dcache_lock);
dput(dentry);
} else {
Index: linux-2.6/fs/configfs/configfs_internal.h
===================================================================
--- linux-2.6.orig/fs/configfs/configfs_internal.h
+++ linux-2.6/fs/configfs/configfs_internal.h
@@ -121,6 +121,7 @@ static inline struct config_item *config
struct config_item * item = NULL;

spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
if (!d_unhashed(dentry)) {
struct configfs_dirent * sd = dentry->d_fsdata;
if (sd->s_type & CONFIGFS_ITEM_LINK) {
@@ -129,6 +130,7 @@ static inline struct config_item *config
} else
item = config_item_get(sd->s_element);
}
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);

return item;
Index: linux-2.6/fs/ocfs2/dcache.c
===================================================================
--- linux-2.6.orig/fs/ocfs2/dcache.c
+++ linux-2.6/fs/ocfs2/dcache.c
@@ -156,13 +156,16 @@ struct dentry *ocfs2_find_local_alias(st
list_for_each(p, &inode->i_dentry) {
dentry = list_entry(p, struct dentry, d_alias);

+ spin_lock(&dentry->d_lock);
if (ocfs2_match_dentry(dentry, parent_blkno, skip_unhashed)) {
mlog(0, "dentry found: %.*s\n",
dentry->d_name.len, dentry->d_name.name);

- dget_locked(dentry);
+ dget_locked_dlock(dentry);
+ spin_unlock(&dentry->d_lock);
break;
}
+ spin_unlock(&dentry->d_lock);

dentry = NULL;
}
Index: linux-2.6/security/tomoyo/realpath.c
===================================================================
--- linux-2.6.orig/security/tomoyo/realpath.c
+++ linux-2.6/security/tomoyo/realpath.c
@@ -17,6 +17,7 @@
#include <linux/magic.h>
#include <linux/slab.h>
#include "common.h"
+#include "../../fs/internal.h"

/**
* tomoyo_encode: Convert binary string to ascii string.
@@ -92,8 +93,10 @@ int tomoyo_realpath_from_path2(struct pa
struct path ns_root = {.mnt = NULL, .dentry = NULL};

spin_lock(&dcache_lock);
+ br_read_lock(vfsmount_lock);
/* go to whatever namespace root we are under */
sp = __d_path(path, &ns_root, newname, newname_len);
+ br_read_unlock(vfsmount_lock);
spin_unlock(&dcache_lock);
/* Prepend "/proc" prefix if using internal proc vfs mount. */
if (!IS_ERR(sp) && (path->mnt->mnt_flags & MNT_INTERNAL) &&
Index: linux-2.6/drivers/usb/core/inode.c
===================================================================
--- linux-2.6.orig/drivers/usb/core/inode.c
+++ linux-2.6/drivers/usb/core/inode.c
@@ -351,10 +351,13 @@ static int usbfs_empty (struct dentry *d

list_for_each(list, &dentry->d_subdirs) {
struct dentry *de = list_entry(list, struct dentry, d_u.d_child);
+ spin_lock(&de->d_lock);
if (usbfs_positive(de)) {
+ spin_unlock(&de->d_lock);
spin_unlock(&dcache_lock);
return 0;
}
+ spin_unlock(&de->d_lock);
}

spin_unlock(&dcache_lock);
Index: linux-2.6/fs/ceph/dir.c
===================================================================
--- linux-2.6.orig/fs/ceph/dir.c
+++ linux-2.6/fs/ceph/dir.c
@@ -135,6 +135,7 @@ more:
fi->at_end = 1;
goto out_unlock;
}
+ spin_lock(&dentry->d_lock);
if (!d_unhashed(dentry) && dentry->d_inode &&
ceph_snap(dentry->d_inode) != CEPH_SNAPDIR &&
ceph_ino(dentry->d_inode) != CEPH_INO_CEPH &&
@@ -144,13 +145,13 @@ more:
dentry->d_name.len, dentry->d_name.name, di->offset,
filp->f_pos, d_unhashed(dentry) ? " unhashed" : "",
!dentry->d_inode ? " null" : "");
+ spin_unlock(&dentry->d_lock);
p = p->prev;
dentry = list_entry(p, struct dentry, d_u.d_child);
di = ceph_dentry(dentry);
}

- spin_lock(&dentry->d_lock);
- dentry->d_count++;
+ dget_dlock(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
spin_unlock(&inode->i_lock);


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