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ANDROID: vfs: add d_canonical_path for stacked filesystem support

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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: 70706497
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>
This commit is contained in:
Daniel Rosenberg
2016-02-11 16:44:15 -08:00
committed by Alistair Delva
parent e2b3aa25c5
commit b05bef535d
3 changed files with 21 additions and 2 deletions
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15
fs/notify/inotify/inotify_user.c
View File

@@ -694,6 +694,8 @@ SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname,
struct fsnotify_group *group; struct fsnotify_group *group;
struct inode *inode; struct inode *inode;
struct path path; struct path path;
struct path alteredpath;
struct path *canonical_path = &path;
struct fd f; struct fd f;
int ret; int ret;
unsigned flags = 0; unsigned flags = 0;
@@ -739,13 +741,22 @@ SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname,
if (ret) if (ret)
goto fput_and_out; 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 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; group = f.file->private_data;
/* create/update an inode mark */ /* create/update an inode mark */
ret = inotify_update_watch(group, inode, mask); ret = inotify_update_watch(group, inode, mask);
path_put(&path); path_put(canonical_path);
fput_and_out: fput_and_out:
fdput(f); fdput(f);
return ret; return ret;

1
include/linux/dcache.h
View File

@@ -147,6 +147,7 @@ struct dentry_operations {
struct vfsmount *(*d_automount)(struct path *); struct vfsmount *(*d_automount)(struct path *);
int (*d_manage)(const struct path *, bool); int (*d_manage)(const struct path *, bool);
struct dentry *(*d_real)(struct dentry *, const struct inode *); struct dentry *(*d_real)(struct dentry *, const struct inode *);
void (*d_canonical_path)(const struct path *, struct path *);
} ____cacheline_aligned; } ____cacheline_aligned;
/* /*

7
include/linux/fsnotify.h
View File

@@ -236,6 +236,7 @@ static inline void fsnotify_modify(struct file *file)
static inline void fsnotify_open(struct file *file) static inline void fsnotify_open(struct file *file)
{ {
const struct path *path = &file->f_path; const struct path *path = &file->f_path;
struct path lower_path;
struct inode *inode = file_inode(file); struct inode *inode = file_inode(file);
__u32 mask = FS_OPEN; __u32 mask = FS_OPEN;
@@ -244,6 +245,12 @@ static inline void fsnotify_open(struct file *file)
if (file->f_flags & __FMODE_EXEC) if (file->f_flags & __FMODE_EXEC)
mask |= FS_OPEN_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); fsnotify_path(inode, path, mask);
} }