From 735236039d54a5a426e774ee275f9cb2585f30dc Mon Sep 17 00:00:00 2001 From: Daniel Rosenberg Date: Thu, 11 Feb 2016 16:44:15 -0800 Subject: [PATCH] vfs: add d_canonical_path for stacked filesystem support Inotify does not currently know when a filesystem is acting as a wrapper around another fs. This means that inotify watchers will miss any modifications to the base file, as well as any made in a separate stacked fs that points to the same file. d_canonical_path solves this problem by allowing the fs to map a dentry to a path in the lower fs. Inotify can use it to find the appropriate place to watch to be informed of all changes to a file. Change-Id: I09563baffad1711a045e45c1bd0bd8713c2cc0b6 Signed-off-by: Daniel Rosenberg --- fs/notify/inotify/inotify_user.c | 17 ++++++++++++++--- include/linux/dcache.h | 1 + 2 files changed, 15 insertions(+), 3 deletions(-) diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c index b8d08d0d0a4d..9a0cd02cf3dc 100644 --- a/fs/notify/inotify/inotify_user.c +++ b/fs/notify/inotify/inotify_user.c @@ -702,6 +702,8 @@ SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname, struct fsnotify_group *group; struct inode *inode; struct path path; + struct path alteredpath; + struct path *canonical_path = &path; struct fd f; int ret; unsigned flags = 0; @@ -741,13 +743,22 @@ SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname, if (ret) goto fput_and_out; + /* support stacked filesystems */ + if(path.dentry && path.dentry->d_op) { + if (path.dentry->d_op->d_canonical_path) { + path.dentry->d_op->d_canonical_path(path.dentry, &alteredpath); + canonical_path = &alteredpath; + path_put(&path); + } + } + /* inode held in place by reference to path; group by fget on fd */ - inode = path.dentry->d_inode; + inode = canonical_path->dentry->d_inode; group = f.file->private_data; /* create/update an inode mark */ ret = inotify_update_watch(group, inode, mask); - path_put(&path); + path_put(canonical_path); fput_and_out: fdput(f); return ret; @@ -814,7 +825,7 @@ static int __init inotify_user_setup(void) BUILD_BUG_ON(IN_ISDIR != FS_ISDIR); BUILD_BUG_ON(IN_ONESHOT != FS_IN_ONESHOT); - BUG_ON(hweight32(ALL_INOTIFY_BITS) != 21); + BUG_ON(hweight32(ALL_INOTIFY_BITS) != 22); inotify_inode_mark_cachep = KMEM_CACHE(inotify_inode_mark, SLAB_PANIC); diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 8a2e009c8a5a..e7041ec48af8 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -161,6 +161,7 @@ struct dentry_operations { struct vfsmount *(*d_automount)(struct path *); int (*d_manage)(struct dentry *, bool); struct inode *(*d_select_inode)(struct dentry *, unsigned); + void (*d_canonical_path)(const struct dentry *, struct path *); } ____cacheline_aligned; /* -- 2.34.1