This is a re-submission of the patch I sent about a month ago.
While working on my code I realized that d_drop() might race against __d_lookup(). __d_drop() (which is called by d_drop() after acquiring the dcache_lock) is accessing dentry->d_flags to set the DCACHE_UNHASHED flag. This shouldn't be done without holding dentry->d_lock, like stated in dcache.h:
struct dentry {
...
unsigned int d_flags; /* protected by d_lock */
...
};Therefore d_drop() must acquire the dentry->d_lock. Likewise every use of __d_drop() must acquire that lock.
This patch fixes d_drop() and every grep'able __d_drop() use. This patch is against today's http://linux.bkbits.net/linux-2.5.
Comments please, Jan
Signed-off-by: Jan Blunck <[EMAIL PROTECTED]>
fs/autofs4/root.c | 2 ++
fs/dcache.c | 3 +++
fs/namei.c | 14 +++++---------
fs/proc/base.c | 6 +++++-
fs/sysfs/inode.c | 6 +++++-
include/linux/dcache.h | 2 ++
6 files changed, 22 insertions(+), 11 deletions(-)
Index: testing-um/include/linux/dcache.h
===================================================================
--- testing-um.orig/include/linux/dcache.h
+++ testing-um/include/linux/dcache.h
@@ -186,7 +186,9 @@ static inline void __d_drop(struct dentr
static inline void d_drop(struct dentry *dentry)
{
spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
__d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
}
Index: testing-um/fs/namei.c
===================================================================
--- testing-um.orig/fs/namei.c
+++ testing-um/fs/namei.c
@@ -1685,17 +1685,13 @@ out:
void dentry_unhash(struct dentry *dentry)
{
dget(dentry);
- spin_lock(&dcache_lock);
- switch (atomic_read(&dentry->d_count)) {
- default:
- spin_unlock(&dcache_lock);
+ if (atomic_read(&dentry->d_count))
shrink_dcache_parent(dentry);
- spin_lock(&dcache_lock);
- if (atomic_read(&dentry->d_count) != 2)
- break;
- case 2:
+ spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
+ if (atomic_read(&dentry->d_count) == 2)
__d_drop(dentry);
- }
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
}
Index: testing-um/fs/sysfs/inode.c
===================================================================
--- testing-um.orig/fs/sysfs/inode.c
+++ testing-um/fs/sysfs/inode.c
@@ -129,13 +129,17 @@ void sysfs_drop_dentry(struct sysfs_dire
if (dentry) {
spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
if (!(d_unhashed(dentry) && dentry->d_inode)) {
dget_locked(dentry);
__d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
simple_unlink(parent->d_inode, dentry);
- } else
+ } else {
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
+ }
}
}
Index: testing-um/fs/dcache.c
===================================================================
--- testing-um.orig/fs/dcache.c
+++ testing-um/fs/dcache.c
@@ -340,13 +340,16 @@ restart:
tmp = head;
while ((tmp = tmp->next) != head) {
struct dentry *dentry = list_entry(tmp, struct dentry, d_alias);
+ spin_lock(&dentry->d_lock);
if (!atomic_read(&dentry->d_count)) {
__dget_locked(dentry);
__d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
dput(dentry);
goto restart;
}
+ spin_unlock(&dentry->d_lock);
}
spin_unlock(&dcache_lock);
}
Index: testing-um/fs/autofs4/root.c
===================================================================
--- testing-um.orig/fs/autofs4/root.c
+++ testing-um/fs/autofs4/root.c
@@ -605,7 +605,9 @@ static int autofs4_dir_rmdir(struct inod
spin_unlock(&dcache_lock);
return -ENOTEMPTY;
}
+ spin_lock(&dentry->d_lock);
__d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
dput(ino->dentry);
Index: testing-um/fs/proc/base.c
===================================================================
--- testing-um.orig/fs/proc/base.c
+++ testing-um/fs/proc/base.c
@@ -1630,11 +1630,15 @@ struct dentry *proc_pid_unhash(struct ta
if (proc_dentry != NULL) {
spin_lock(&dcache_lock);
+ spin_lock(&proc_dentry->d_lock);
if (!d_unhashed(proc_dentry)) {
dget_locked(proc_dentry);
__d_drop(proc_dentry);
- } else
+ spin_unlock(&proc_dentry->d_lock);
+ } else {
+ spin_unlock(&proc_dentry->d_lock);
proc_dentry = NULL;
+ }
spin_unlock(&dcache_lock);
}
return proc_dentry;
