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| author | Tejun Heo <htejun@gmail.com> | 2007-06-11 09:04:01 +0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2007-06-13 03:08:47 +0400 |
| commit | dd14cbc994709a1c5a64ed3621f583c49a27e521 (patch) | |
| tree | e48d38b7450661907c7b75490504c7f70b04d6cc /fs/sysfs/inode.c | |
| parent | 6aa054aadfea613a437ad0b15d38eca2b963fc0a (diff) | |
| download | linux-dd14cbc994709a1c5a64ed3621f583c49a27e521.tar.xz | |
sysfs: fix race condition around sd->s_dentry, take#2
Allowing attribute and symlink dentries to be reclaimed means
sd->s_dentry can change dynamically. However, updates to the field
are unsynchronized leading to race conditions. This patch adds
sysfs_lock and use it to synchronize updates to sd->s_dentry.
Due to the locking around ->d_iput, the check in sysfs_drop_dentry()
is complex. sysfs_lock only protect sd->s_dentry pointer itself. The
validity of the dentry is protected by dcache_lock, so whether dentry
is alive or not can only be tested while holding both locks.
This is minimal backport of sysfs_drop_dentry() rewrite in devel
branch.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'fs/sysfs/inode.c')
| -rw-r--r-- | fs/sysfs/inode.c | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/fs/sysfs/inode.c b/fs/sysfs/inode.c index 38bbe071cc15..5266eec15f6e 100644 --- a/fs/sysfs/inode.c +++ b/fs/sysfs/inode.c @@ -246,9 +246,23 @@ static inline void orphan_all_buffers(struct inode *node) */ void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent) { - struct dentry * dentry = sd->s_dentry; + struct dentry *dentry = NULL; struct inode *inode; + /* We're not holding a reference to ->s_dentry dentry but the + * field will stay valid as long as sysfs_lock is held. + */ + spin_lock(&sysfs_lock); + spin_lock(&dcache_lock); + + /* dget dentry if it's still alive */ + if (sd->s_dentry && sd->s_dentry->d_inode) + dentry = dget_locked(sd->s_dentry); + + spin_unlock(&dcache_lock); + spin_unlock(&sysfs_lock); + + /* drop dentry */ if (dentry) { spin_lock(&dcache_lock); spin_lock(&dentry->d_lock); @@ -268,6 +282,8 @@ void sysfs_drop_dentry(struct sysfs_dirent * sd, struct dentry * parent) spin_unlock(&dentry->d_lock); spin_unlock(&dcache_lock); } + + dput(dentry); } } |