diff options
Diffstat (limited to 'fs/overlayfs/inode.c')
| -rw-r--r-- | fs/overlayfs/inode.c | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index bfebef7638ca..13981b0a8235 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -527,6 +527,27 @@ static const struct address_space_operations ovl_aops = { * [...] &ovl_i_mutex_dir_key[depth] (stack_depth=2) * [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1) * [...] &type->i_mutex_dir_key (stack_depth=0) + * + * Locking order w.r.t ovl_want_write() is important for nested overlayfs. + * + * This chain is valid: + * - inode->i_rwsem (inode_lock[2]) + * - upper_mnt->mnt_sb->s_writers (ovl_want_write[0]) + * - OVL_I(inode)->lock (ovl_inode_lock[2]) + * - OVL_I(lowerinode)->lock (ovl_inode_lock[1]) + * + * And this chain is valid: + * - inode->i_rwsem (inode_lock[2]) + * - OVL_I(inode)->lock (ovl_inode_lock[2]) + * - lowerinode->i_rwsem (inode_lock[1]) + * - OVL_I(lowerinode)->lock (ovl_inode_lock[1]) + * + * But lowerinode->i_rwsem SHOULD NOT be acquired while ovl_want_write() is + * held, because it is in reverse order of the non-nested case using the same + * upper fs: + * - inode->i_rwsem (inode_lock[1]) + * - upper_mnt->mnt_sb->s_writers (ovl_want_write[0]) + * - OVL_I(inode)->lock (ovl_inode_lock[1]) */ #define OVL_MAX_NESTING FILESYSTEM_MAX_STACK_DEPTH |