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ovl: implement lookup in data-only layers

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Lookup in data-only layers only for a lower metacopy with an absolute
redirect xattr.

The metacopy xattr is not checked on files found in the data-only layers
and redirect xattr are not followed in the data-only layers.

Reviewed-by: Alexander Larsson <alexl@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Amir Goldstein 2023-04-27 14:52:13 +03:00
parent 37ebf056d6
commit 5436ab0a86
1 changed files with 72 additions and 1 deletions
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73
fs/overlayfs/namei.c
View file

@ -14,6 +14,8 @@
#include <linux/exportfs.h>
#include "overlayfs.h"
#include "../internal.h" /* for vfs_path_lookup */
struct ovl_lookup_data {
struct super_block *sb;
struct vfsmount *mnt;
@ -24,6 +26,8 @@ struct ovl_lookup_data {
bool last;
char *redirect;
bool metacopy;
/* Referring to last redirect xattr */
bool absolute_redirect;
};
static int ovl_check_redirect(const struct path *path, struct ovl_lookup_data *d,
@ -33,11 +37,13 @@ static int ovl_check_redirect(const struct path *path, struct ovl_lookup_data *d
char *buf;
struct ovl_fs *ofs = OVL_FS(d->sb);
d->absolute_redirect = false;
buf = ovl_get_redirect_xattr(ofs, path, prelen + strlen(post));
if (IS_ERR_OR_NULL(buf))
return PTR_ERR(buf);
if (buf[0] == '/') {
d->absolute_redirect = true;
/*
* One of the ancestor path elements in an absolute path
* lookup in ovl_lookup_layer() could have been opaque and
@ -349,6 +355,61 @@ static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
return 0;
}
static int ovl_lookup_data_layer(struct dentry *dentry, const char *redirect,
const struct ovl_layer *layer,
struct path *datapath)
{
int err;
err = vfs_path_lookup(layer->mnt->mnt_root, layer->mnt, redirect,
LOOKUP_BENEATH | LOOKUP_NO_SYMLINKS | LOOKUP_NO_XDEV,
datapath);
pr_debug("lookup lowerdata (%pd2, redirect=\"%s\", layer=%d, err=%i)\n",
dentry, redirect, layer->idx, err);
if (err)
return err;
err = -EREMOTE;
if (ovl_dentry_weird(datapath->dentry))
goto out_path_put;
err = -ENOENT;
/* Only regular file is acceptable as lower data */
if (!d_is_reg(datapath->dentry))
goto out_path_put;
return 0;
out_path_put:
path_put(datapath);
return err;
}
/* Lookup in data-only layers by absolute redirect to layer root */
static int ovl_lookup_data_layers(struct dentry *dentry, const char *redirect,
struct ovl_path *lowerdata)
{
struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
const struct ovl_layer *layer;
struct path datapath;
int err = -ENOENT;
int i;
layer = &ofs->layers[ofs->numlayer - ofs->numdatalayer];
for (i = 0; i < ofs->numdatalayer; i++, layer++) {
err = ovl_lookup_data_layer(dentry, redirect, layer, &datapath);
if (!err) {
mntput(datapath.mnt);
lowerdata->dentry = datapath.dentry;
lowerdata->layer = layer;
return 0;
}
}
return err;
}
int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
struct dentry *upperdentry, struct ovl_path **stackp)
@ -917,7 +978,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
if (!ofs->config.redirect_follow)
d.last = i == ovl_numlower(poe) - 1;
else
else if (d.is_dir || !ofs->numdatalayer)
d.last = lower.layer->idx == ovl_numlower(roe);
d.mnt = lower.layer->mnt;
@ -1011,6 +1072,16 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
}
}
/* Lookup absolute redirect from lower metacopy in data-only layers */
if (d.metacopy && ctr && ofs->numdatalayer && d.absolute_redirect) {
err = ovl_lookup_data_layers(dentry, d.redirect,
&stack[ctr]);
if (!err) {
d.metacopy = false;
ctr++;
}
}
/*
* For regular non-metacopy upper dentries, there is no lower
* path based lookup, hence ctr will be zero. If a dentry is found