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Date: Sun, 4 Oct 2020 22:24:01 +0300
From: Alexander Mikhalitsyn <alexander.mikhalitsyn@...tuozzo.com>
To: miklos@...redi.hu
Cc: Alexander Mikhalitsyn <alexander.mikhalitsyn@...tuozzo.com>,
Amir Goldstein <amir73il@...il.com>,
Andrei Vagin <avagin@...il.com>,
Pavel Tikhomirov <ptikhomirov@...tuozzo.com>,
David Howells <dhowells@...hat.com>,
linux-unionfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH 1/1] overlayfs: add ioctls that allows to get fhandle for layers dentries
Add several ioctls to ovl_dir_operations that allows to get file handles
for upperdir, workdir, lowerdir dentries. Special {s_dev; fhandle}
format used. (Ideally should be {mnt_id; fhandle} but this impossible
because overlayfs not keeps mounts refcnt for layers.)
Added ioctls list:
OVL_IOC_GETLWRFHNDLSNUM - get lowerdirs count
OVL_IOC_GETLWRFHNDL - get i-th lowerdir fhandle
OVL_IOC_GETUPPRFHNDL - get upperdir fhandle
OVL_IOC_GETWRKFHNDL - get workdir fhandle
Cc: Amir Goldstein <amir73il@...il.com>
Cc: Andrei Vagin <avagin@...il.com>
Cc: Pavel Tikhomirov <ptikhomirov@...tuozzo.com>
Cc: Miklos Szeredi <miklos@...redi.hu>
Cc: David Howells <dhowells@...hat.com>
Cc: linux-unionfs@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn@...tuozzo.com>
---
fs/overlayfs/readdir.c | 160 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 160 insertions(+)
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 596002054ac6..12ee043d2b3a 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -13,6 +13,7 @@
#include <linux/security.h>
#include <linux/cred.h>
#include <linux/ratelimit.h>
+#include <linux/exportfs.h>
#include "overlayfs.h"
struct ovl_cache_entry {
@@ -58,6 +59,20 @@ struct ovl_dir_file {
struct file *upperfile;
};
+struct ovl_mnt_opt_fh {
+ __u32 s_dev;
+ struct file_handle fh;
+ /* use f_handle field from struct file_handle */
+ __u8 __fhdata[MAX_HANDLE_SZ];
+};
+
+struct ovl_mnt_opt_fh_req {
+ union {
+ unsigned int lowernum;
+ struct ovl_mnt_opt_fh result;
+ };
+} __packed;
+
static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
{
return rb_entry(n, struct ovl_cache_entry, node);
@@ -942,6 +957,150 @@ static int ovl_dir_open(struct inode *inode, struct file *file)
return 0;
}
+static long ovl_ioctl_get_lowers_num(struct super_block *sb)
+{
+ struct ovl_entry *oe = sb->s_root->d_fsdata;
+ return oe->numlower;
+}
+
+static struct ovl_mnt_opt_fh *__ovl_encode_mnt_opt_fh(struct dentry *dentry)
+{
+ struct ovl_mnt_opt_fh *opt_fh;
+ int fh_type, dwords;
+ int buflen = MAX_HANDLE_SZ;
+ int err;
+
+ opt_fh = kzalloc(sizeof(struct ovl_mnt_opt_fh), GFP_KERNEL);
+ if (!opt_fh)
+ return ERR_PTR(-ENOMEM);
+
+ /* we ask for a non connected handle */
+ dwords = buflen >> 2;
+ fh_type = exportfs_encode_fh(dentry, (void *)opt_fh->fh.f_handle, &dwords, 0);
+ buflen = (dwords << 2);
+
+ err = -EIO;
+ if (WARN_ON(fh_type < 0) ||
+ WARN_ON(buflen > MAX_HANDLE_SZ) ||
+ WARN_ON(fh_type == FILEID_INVALID))
+ goto out_err;
+
+ opt_fh->fh.handle_type = fh_type;
+ opt_fh->fh.handle_bytes = buflen;
+
+ /*
+ * Ideally, we want to have mnt_id+fhandle, but overlayfs not
+ * keep refcnts on layers mounts and we couldn't determine
+ * mnt_ids for layers. So, let's give s_dev to CRIU.
+ * It's better than nothing.
+ */
+ opt_fh->s_dev = dentry->d_sb->s_dev;
+
+ return opt_fh;
+
+out_err:
+ kfree(opt_fh);
+ return ERR_PTR(err);
+}
+
+static long __ovl_ioctl_get_fhandle(struct dentry *origin,
+ unsigned long arg)
+{
+ struct ovl_mnt_opt_fh *fh;
+ int ret = 0;
+
+ fh = __ovl_encode_mnt_opt_fh(origin);
+ if (IS_ERR(fh))
+ return PTR_ERR(fh);
+
+ if (copy_to_user((struct ovl_mnt_opt_fh __user *)arg,
+ fh, sizeof(*fh)))
+ ret = -EFAULT;
+
+ kfree(fh);
+ return ret;
+}
+
+static long ovl_ioctl_get_lower_fhandle(struct super_block *sb,
+ unsigned long arg)
+{
+ struct ovl_entry *oe = sb->s_root->d_fsdata;
+ struct dentry *origin;
+ struct ovl_mnt_opt_fh_req input;
+
+ BUILD_BUG_ON(sizeof(struct ovl_mnt_opt_fh_req) != sizeof(struct ovl_mnt_opt_fh));
+
+ if (copy_from_user(&input, (struct ovl_mnt_opt_fh_req __user *)arg,
+ sizeof(input)))
+ return -EFAULT;
+
+ if (input.lowernum >= oe->numlower)
+ return -EINVAL;
+
+ origin = oe->lowerstack[input.lowernum].dentry;
+
+ return __ovl_ioctl_get_fhandle(origin, arg);
+}
+
+static long ovl_ioctl_get_upper_fhandle(struct super_block *sb,
+ unsigned long arg)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+ struct dentry *origin;
+
+ if (!ofs->config.upperdir)
+ return -EINVAL;
+
+ origin = OVL_I(d_inode(sb->s_root))->__upperdentry;
+
+ return __ovl_ioctl_get_fhandle(origin, arg);
+}
+
+static long ovl_ioctl_get_work_fhandle(struct super_block *sb,
+ unsigned long arg)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+
+ if (!ofs->config.upperdir)
+ return -EINVAL;
+
+ return __ovl_ioctl_get_fhandle(ofs->workbasedir, arg);
+}
+
+#define OVL_IOC_GETLWRFHNDLSNUM _IO('o', 1)
+// DISCUSS: what if MAX_HANDLE_SZ will change?
+#define OVL_IOC_GETLWRFHNDL _IOR('o', 2, struct ovl_mnt_opt_fh)
+#define OVL_IOC_GETUPPRFHNDL _IOR('o', 3, struct ovl_mnt_opt_fh)
+#define OVL_IOC_GETWRKFHNDL _IOR('o', 4, struct ovl_mnt_opt_fh)
+
+static long ovl_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+ long ret;
+
+ switch (cmd) {
+ case OVL_IOC_GETLWRFHNDLSNUM:
+ ret = ovl_ioctl_get_lowers_num(file_inode(file)->i_sb);
+ break;
+
+ case OVL_IOC_GETLWRFHNDL:
+ ret = ovl_ioctl_get_lower_fhandle(file_inode(file)->i_sb, arg);
+ break;
+
+ case OVL_IOC_GETUPPRFHNDL:
+ ret = ovl_ioctl_get_upper_fhandle(file_inode(file)->i_sb, arg);
+ break;
+
+ case OVL_IOC_GETWRKFHNDL:
+ ret = ovl_ioctl_get_work_fhandle(file_inode(file)->i_sb, arg);
+ break;
+
+ default:
+ ret = -ENOTTY;
+ }
+
+ return ret;
+}
+
const struct file_operations ovl_dir_operations = {
.read = generic_read_dir,
.open = ovl_dir_open,
@@ -949,6 +1108,7 @@ const struct file_operations ovl_dir_operations = {
.llseek = ovl_dir_llseek,
.fsync = ovl_dir_fsync,
.release = ovl_dir_release,
+ .unlocked_ioctl = ovl_ioctl,
};
int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
--
2.25.1
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