AuxXxilium/linux_dsm_epyc7002
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Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Browse Source 
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
This commit is contained in:
Linus Torvalds 2018-03-15 18:57:14 -07:00
commit df09348f78
4 changed files with 22 additions and 7 deletions
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21
fs/dcache.c
View File

@ -647,11 +647,16 @@ static inline struct dentry *lock_parent(struct dentry *dentry)
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 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
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;

5
fs/namei.c
View File

@ -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);

2
fs/nfs/super.c
View File

@ -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);

1
include/linux/fs.h
View File

@ -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 */