Evolution-X-Devices/kernel_nothing_sm7325
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

ANDROID: vfs: add d_canonical_path for stacked filesystem support

Browse Source 
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.

Test: HiKey/X15 + Pie + android-mainline,
      and HiKey + AOSP Maser + android-mainline,
      directories under /sdcard created,
      output of mount is right,
      CTS test collecting device infor works

Bug: 171780975
Change-Id: I09563baffad1711a045e45c1bd0bd8713c2cc0b6
Signed-off-by: Daniel Rosenberg <drosen@google.com>
[astrachan: Folded 34df4102216e ("ANDROID: fsnotify: Notify lower fs of
            open") into this patch]
Signed-off-by: Alistair Strachan <astrachan@google.com>
Signed-off-by: Yongqin Liu <yongqin.liu@linaro.org>
Signed-off-by: Alessio Balsini <balsini@google.com>
This commit is contained in:
Alessio Balsini
2020-10-27 13:24:03 +00:00
committed by Greg Kroah-Hartman
parent aa445f97a0
commit 854f380681
3 changed files with 22 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

16
fs/notify/inotify/inotify_user.c
View File

@@ -701,6 +701,8 @@ 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;
@@ -747,13 +749,23 @@ 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,
&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;

1
include/linux/dcache.h
View File

@@ -151,6 +151,7 @@ struct dentry_operations {
struct vfsmount *(*d_automount)(struct path *);
int (*d_manage)(const struct path *, bool);
struct dentry *(*d_real)(struct dentry *, const struct inode *);
void (*d_canonical_path)(const struct path *, struct path *);
ANDROID_KABI_RESERVE(1);
ANDROID_KABI_RESERVE(2);

7
include/linux/fsnotify.h
View File

@@ -262,6 +262,7 @@ static inline void fsnotify_modify(struct file *file)
static inline void fsnotify_open(struct file *file)
{
const struct path *path = &file->f_path;
struct path lower_path;
struct inode *inode = file_inode(file);
__u32 mask = FS_OPEN;
@@ -270,6 +271,12 @@ static inline void fsnotify_open(struct file *file)
if (file->f_flags & __FMODE_EXEC)
mask |= FS_OPEN_EXEC;
if (path->dentry->d_op && path->dentry->d_op->d_canonical_path) {
path->dentry->d_op->d_canonical_path(path, &lower_path);
fsnotify_parent(&lower_path, NULL, mask);
fsnotify(lower_path.dentry->d_inode, mask, &lower_path, FSNOTIFY_EVENT_PATH, NULL, 0);
path_put(&lower_path);
}
fsnotify_path(inode, path, mask);
}