On Tue, Jul 31, 2018 at 02:10:42PM -0700, Mark Fasheh wrote:
> diff --git a/fs/stat.c b/fs/stat.c
> index f8e6fb2c3657..80ea42505219 100644
> --- a/fs/stat.c
> +++ b/fs/stat.c
> @@ -84,6 +84,29 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
> }
> EXPORT_SYMBOL(vfs_getattr_nosec);
>
> +void vfs_map_unique_ino_dev(struct dentry *dentry, u64 *ino, dev_t *dev)
> +{
> + int ret;
> + struct path path;
> + struct kstat stat;
> +
> + path.mnt = NULL;
> + path.dentry = dentry;
> + /* ->dev is always returned, so we only need to specify ino here */
> + ret = vfs_getattr_nosec(&path, &stat, STATX_INO, 0);
> + if (ret) {
> + struct inode *inode = d_inode(dentry);
> + /* Fallback to old behavior in case of getattr error */
> + *ino = inode->i_ino;
> + *dev = inode->i_sb->s_dev;
> + return ret;
Ooof, attached is a version of this patch which doesn't try to return a value
from a void function. Apologies for the extra e-mail.
>From Mark Fasheh <mfasheh@xxxxxxx>
[PATCH 1/4] vfs: introduce function to map unique ino/dev pairs
There are places in the VFS where we export an ino/dev pair to userspace.
/proc/PID/maps is a good example - we directly expose inode->i_ino and
inode->i_sb->s_dev to userspace there. Many filesystems don't put a unique
value in inode->i_ino and instead rely on ->getattr to provide the real
inode number to userspace. super->s_dev is similar - some filesystems
expose a difference device from what's put in super->s_dev when queried via
stat/statx.
Ultimately this makes it impossible for a user (or software) to match one of
those reported pairs to the right inode.
We can fix this by adding a helper function, vfs_map_unique_ino_dev(), which
will query the owning filesystem (via ->getattr) to get the correct ino/dev
pair. Later patches will update those places which simply dump inode->i_ino
and super->s_dev to use the helper.
Signed-off-by: Mark Fasheh <mfasheh@xxxxxxx>
---
fs/stat.c | 22 ++++++++++++++++++++++
include/linux/fs.h | 2 ++
2 files changed, 24 insertions(+)
diff --git a/fs/stat.c b/fs/stat.c
index f8e6fb2c3657..20c72d618ed5 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -84,6 +84,28 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat,
}
EXPORT_SYMBOL(vfs_getattr_nosec);
+void vfs_map_unique_ino_dev(struct dentry *dentry, u64 *ino, dev_t *dev)
+{
+ int ret;
+ struct path path;
+ struct kstat stat;
+
+ path.mnt = NULL;
+ path.dentry = dentry;
+ /* ->dev is always returned, so we only need to specify ino here */
+ ret = vfs_getattr_nosec(&path, &stat, STATX_INO, 0);
+ if (ret) {
+ struct inode *inode = d_inode(dentry);
+ /* Fallback to old behavior in case of getattr error */
+ *ino = inode->i_ino;
+ *dev = inode->i_sb->s_dev;
+ return;
+ }
+ *ino = stat.ino;
+ *dev = stat.dev;
+}
+EXPORT_SYMBOL(vfs_map_unique_ino_dev);
+
/*
* vfs_getattr - Get the enhanced basic attributes of a file
* @path: The file of interest
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d78d146a98da..b80789472438 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3077,6 +3077,8 @@ extern void kfree_link(void *);
extern void generic_fillattr(struct inode *, struct kstat *);
extern int vfs_getattr_nosec(const struct path *, struct kstat *, u32, unsigned int);
extern int vfs_getattr(const struct path *, struct kstat *, u32, unsigned int);
+extern void vfs_map_unique_ino_dev(struct dentry *dentry, u64 *ino, dev_t *dev);
+
void __inode_add_bytes(struct inode *inode, loff_t bytes);
void inode_add_bytes(struct inode *inode, loff_t bytes);
void __inode_sub_bytes(struct inode *inode, loff_t bytes);
--
2.15.1
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