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authorLinus Torvalds <torvalds@linux-foundation.org>2018-03-15 18:57:14 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-03-15 18:57:14 -0700
commitdf09348f78dc53a14faddca4414d66bea849a749 (patch)
tree79d0bda31965824ad7272118f432ddd67e4e5db5
parentcfb61b5e3e09f8b49bc4d685429df75f45127adc (diff)
parent95dd77580ccd66a0da96e6d4696945b8cea39431 (diff)
downloadlinux-sh-df09348f78dc53a14faddca4414d66bea849a749.tar.gz
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs fixes from Al Viro: - backport-friendly part of lock_parent() race fix - a fix for an assumption in the heurisic used by path_connected() that is not true on NFS - livelock fixes for d_alloc_parallel() * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: fs: Teach path_connected to handle nfs filesystems with multiple roots. fs: dcache: Use READ_ONCE when accessing i_dir_seq fs: dcache: Avoid livelock between d_alloc_parallel and __d_add lock_parent() needs to recheck if dentry got __dentry_kill'ed under it
-rw-r--r--fs/dcache.c21
-rw-r--r--fs/namei.c5
-rw-r--r--fs/nfs/super.c2
-rw-r--r--include/linux/fs.h1
4 files changed, 22 insertions, 7 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 7c38f39958bc..8945e6cabd93 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -647,11 +647,16 @@ again:
spin_unlock(&parent->d_lock);
goto again;
}
- rcu_read_unlock();
- if (parent != dentry)
+ if (parent != dentry) {
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
- else
+ if (unlikely(dentry->d_lockref.count < 0)) {
+ spin_unlock(&parent->d_lock);
+ parent = NULL;
+ }
+ } else {
parent = NULL;
+ }
+ rcu_read_unlock();
return parent;
}
@@ -2474,7 +2479,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
retry:
rcu_read_lock();
- seq = smp_load_acquire(&parent->d_inode->i_dir_seq) & ~1;
+ seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
r_seq = read_seqbegin(&rename_lock);
dentry = __d_lookup_rcu(parent, name, &d_seq);
if (unlikely(dentry)) {
@@ -2495,8 +2500,14 @@ retry:
rcu_read_unlock();
goto retry;
}
+
+ if (unlikely(seq & 1)) {
+ rcu_read_unlock();
+ goto retry;
+ }
+
hlist_bl_lock(b);
- if (unlikely(parent->d_inode->i_dir_seq != seq)) {
+ if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
hlist_bl_unlock(b);
rcu_read_unlock();
goto retry;
diff --git a/fs/namei.c b/fs/namei.c
index 921ae32dbc80..cafa365eeb70 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -559,9 +559,10 @@ static int __nd_alloc_stack(struct nameidata *nd)
static bool path_connected(const struct path *path)
{
struct vfsmount *mnt = path->mnt;
+ struct super_block *sb = mnt->mnt_sb;
- /* Only bind mounts can have disconnected paths */
- if (mnt->mnt_root == mnt->mnt_sb->s_root)
+ /* Bind mounts and multi-root filesystems can have disconnected paths */
+ if (!(sb->s_iflags & SB_I_MULTIROOT) && (mnt->mnt_root == sb->s_root))
return true;
return is_subdir(path->dentry, mnt->mnt_root);
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 29bacdc56f6a..5e470e233c83 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -2631,6 +2631,8 @@ struct dentry *nfs_fs_mount_common(struct nfs_server *server,
/* initial superblock/root creation */
mount_info->fill_super(s, mount_info);
nfs_get_cache_cookie(s, mount_info->parsed, mount_info->cloned);
+ if (!(server->flags & NFS_MOUNT_UNSHARED))
+ s->s_iflags |= SB_I_MULTIROOT;
}
mntroot = nfs_get_root(s, mount_info->mntfh, dev_name);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 79c413985305..c6baf767619e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1317,6 +1317,7 @@ extern int send_sigurg(struct fown_struct *fown);
#define SB_I_CGROUPWB 0x00000001 /* cgroup-aware writeback enabled */
#define SB_I_NOEXEC 0x00000002 /* Ignore executables on this fs */
#define SB_I_NODEV 0x00000004 /* Ignore devices on this fs */
+#define SB_I_MULTIROOT 0x00000008 /* Multiple roots to the dentry tree */
/* sb->s_iflags to limit user namespace mounts */
#define SB_I_USERNS_VISIBLE 0x00000010 /* fstype already mounted */