On an overlayfs instance having lower and upper dirs on the same
filesystem, stat(2) on a file residing on the lower dir will
provide st_dev corresponding to the lower filesystem's bdev. Later, After
the lower file is copied-up, stat(2) on the file provides st_dev
corresponding to the overlayfs' pseudo device. Hence we have a mismatch
in the st_dev value that is provided to the userspace.
This commit allocates pseudo bdevs for each of the lowerdirs and
provides the value of such a pseudo bdev for stat(2) on files that
either reside only on the lower dir or have been copied up from a
file that was originally present on the lowedir.
Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
---
fs/overlayfs/inode.c | 24 ++++++++++++++++++++++--
fs/overlayfs/ovl_entry.h | 9 ++++++++-
fs/overlayfs/super.c | 34 ++++++++++++++++++++++++++--------
3 files changed, 56 insertions(+), 11 deletions(-)
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index d613e2c..8f6d66c 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -8,11 +8,28 @@
*/
#include <linux/fs.h>
+#include <linux/mount.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/xattr.h>
#include <linux/posix_acl.h>
#include "overlayfs.h"
+#include "ovl_entry.h"
+
+static dev_t ovl_get_pseudo_dev(struct ovl_fs *ofs, dev_t dev)
+{
+ int i;
+
+ if (ofs->upper_mnt && ofs->upper_mnt->mnt_sb->s_dev == dev)
+ return ofs->ovl_sb->s_dev;
+
+ for (i = 0; i < ofs->numlower; i++) {
+ if (ofs->lower_mnt[i].real_dev == dev)
+ return ofs->lower_mnt[i].pseudo_dev;
+ }
+
+ return dev;
+}
int ovl_setattr(struct dentry *dentry, struct iattr *attr)
{
@@ -100,10 +117,13 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
* upper files, so we cannot use the lower origin st_ino
* for those different files, even for the same fs case.
*/
- if (is_dir || lowerstat.nlink == 1)
+ if (is_dir || lowerstat.nlink == 1) {
stat->ino = lowerstat.ino;
+ stat->dev = lowerstat.dev;
+ }
}
- stat->dev = dentry->d_sb->s_dev;
+ stat->dev = ovl_get_pseudo_dev(dentry->d_sb->s_fs_info,
+ stat->dev);
} else if (is_dir) {
/*
* If not all layers are on the same fs the pair {real st_ino;
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 34bc4a9..f15900a 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -16,11 +16,17 @@ struct ovl_config {
bool redirect_dir;
};
+struct ovl_lower_mnt {
+ struct vfsmount *mnt;
+ dev_t real_dev;
+ dev_t pseudo_dev;
+};
+
/* private information held for overlayfs's superblock */
struct ovl_fs {
struct vfsmount *upper_mnt;
unsigned numlower;
- struct vfsmount **lower_mnt;
+ struct ovl_lower_mnt *lower_mnt;
struct dentry *workdir;
long namelen;
/* pathnames of lower and upper dirs, for show_options */
@@ -30,6 +36,7 @@ struct ovl_fs {
bool tmpfile;
bool noxattr;
wait_queue_head_t copyup_wq;
+ struct super_block *ovl_sb;
/* sb common to all layers */
struct super_block *same_sb;
};
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 4882ffb..26d3d2d 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -172,8 +172,10 @@ static void ovl_put_super(struct super_block *sb)
dput(ufs->workdir);
mntput(ufs->upper_mnt);
- for (i = 0; i < ufs->numlower; i++)
- mntput(ufs->lower_mnt[i]);
+ for (i = 0; i < ufs->numlower; i++) {
+ mntput(ufs->lower_mnt[i].mnt);
+ free_anon_bdev(ufs->lower_mnt[i].pseudo_dev);
+ }
kfree(ufs->lower_mnt);
kfree(ufs->config.lowerdir);
@@ -908,15 +910,25 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
}
err = -ENOMEM;
- ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
+ ufs->lower_mnt = kcalloc(numlower, sizeof(struct ovl_lower_mnt),
+ GFP_KERNEL);
if (ufs->lower_mnt == NULL)
goto out_put_workdir;
for (i = 0; i < numlower; i++) {
- struct vfsmount *mnt = clone_private_mount(&stack[i]);
+ struct vfsmount *mnt;
+ dev_t dev;
+ err = get_anon_bdev(&dev);
+ if (err) {
+ pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
+ goto out_put_lower_mnt;
+ }
+
+ mnt = clone_private_mount(&stack[i]);
err = PTR_ERR(mnt);
if (IS_ERR(mnt)) {
pr_err("overlayfs: failed to clone lowerpath\n");
+ free_anon_bdev(dev);
goto out_put_lower_mnt;
}
/*
@@ -925,7 +937,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
*/
mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
- ufs->lower_mnt[ufs->numlower] = mnt;
+ ufs->lower_mnt[ufs->numlower].mnt = mnt;
+ ufs->lower_mnt[ufs->numlower].real_dev = mnt->mnt_sb->s_dev;
+ ufs->lower_mnt[ufs->numlower].pseudo_dev = dev;
ufs->numlower++;
/* Check if all lower layers are on same sb */
@@ -980,7 +994,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
}
for (i = 0; i < numlower; i++) {
oe->lowerstack[i].dentry = stack[i].dentry;
- oe->lowerstack[i].mnt = ufs->lower_mnt[i];
+ oe->lowerstack[i].mnt = ufs->lower_mnt[i].mnt;
}
kfree(stack);
@@ -991,6 +1005,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
ovl_copyattr(realinode, d_inode(root_dentry));
sb->s_root = root_dentry;
+ ufs->ovl_sb = sb;
return 0;
@@ -999,8 +1014,11 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
out_put_cred:
put_cred(ufs->creator_cred);
out_put_lower_mnt:
- for (i = 0; i < ufs->numlower; i++)
- mntput(ufs->lower_mnt[i]);
+ for (i = 0; i < ufs->numlower; i++) {
+ if (ufs->lower_mnt[i].mnt)
+ free_anon_bdev(ufs->lower_mnt[i].pseudo_dev);
+ mntput(ufs->lower_mnt[i].mnt);
+ }
kfree(ufs->lower_mnt);
out_put_workdir:
dput(ufs->workdir);
--
2.9.4
--
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