When redirect_fh is enabled, if overlay.origin xattr is found on a
non-dir upper inode, instead of lookup of the copy up origin in lower
layer by name, try to get it by calling exportfs_decode_fh().
On failure to lookup by file handle to lower layer or if redirect_fh is
disabled, do not lookup the copy up origin by name, because the lower
found by name could be another file in case the upper file was renamed.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/overlayfs/namei.c | 176 +++++++++++++++++++++++++++++++++++++++++++++--
fs/overlayfs/overlayfs.h | 1 +
fs/overlayfs/util.c | 14 ++++
3 files changed, 186 insertions(+), 5 deletions(-)
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 66072b0..695a78e 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -12,6 +12,8 @@
#include <linux/namei.h>
#include <linux/xattr.h>
#include <linux/ratelimit.h>
+#include <linux/mount.h>
+#include <linux/exportfs.h>
#include "overlayfs.h"
#include "ovl_entry.h"
@@ -22,7 +24,10 @@ struct ovl_lookup_data {
bool stop;
bool last;
int idx;
- char *redirect;
+ bool by_path; /* redirect by path: */
+ char *redirect; /* - path to follow */
+ bool by_fh; /* redirect by file handle: */
+ struct ovl_fh *fh; /* - file handle to follow */
};
static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d,
@@ -82,6 +87,51 @@ static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d,
goto err_free;
}
+static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name)
+{
+ int res;
+ void *buf = NULL;
+
+ res = vfs_getxattr(dentry, name, NULL, 0);
+ if (res <= 0) {
+ if (res == -ENODATA || res == -EOPNOTSUPP)
+ return 0;
+ goto fail;
+ }
+ buf = kzalloc(res, GFP_TEMPORARY);
+ if (!buf) {
+ res = -ENOMEM;
+ goto fail;
+ }
+
+ res = vfs_getxattr(dentry, name, buf, res);
+ if (res < 0 || !ovl_redirect_fh_ok(buf, res))
+ goto fail;
+
+ return (struct ovl_fh *)buf;
+
+err_free:
+ kfree(buf);
+ return NULL;
+fail:
+ pr_warn_ratelimited("overlayfs: failed to get %s (%i)\n",
+ name, res);
+ goto err_free;
+}
+
+static void ovl_check_redirect_fh(struct dentry *dentry,
+ struct ovl_lookup_data *d)
+{
+ kfree(d->fh);
+ d->fh = ovl_get_fh(dentry, OVL_XATTR_ORIGIN);
+}
+
+static void ovl_reset_redirect_fh(struct ovl_lookup_data *d)
+{
+ kfree(d->fh);
+ d->fh = NULL;
+}
+
static bool ovl_is_opaquedir(struct dentry *dentry)
{
int res;
@@ -149,9 +199,23 @@ static int ovl_lookup_data(struct dentry *this, struct ovl_lookup_data *d,
* Check redirect dir even if d->last, because with redirect_dir,
* a merge dir may have an opaque dir parent.
*/
- err = ovl_check_redirect(this, d, prelen, post);
- if (err)
- goto out_err;
+ if (d->by_path) {
+ err = ovl_check_redirect(this, d, prelen, post);
+ if (err)
+ goto out_err;
+ }
+ /*
+ * If non-dir has a valid origin file handle, it will be used to
+ * find the copy up origin in lower layers.
+ *
+ * Directory lookup by fh is not desired for all workloads, so it
+ * will be enabled by a future mount option.
+ */
+ if (d->by_fh && !d_is_dir(this)) {
+ ovl_check_redirect_fh(this, d);
+ d->stop = !d->fh;
+ }
+
out:
*ret = this;
return 0;
@@ -225,6 +289,76 @@ static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
return 0;
}
+static struct dentry *ovl_decode_fh(struct vfsmount *mnt,
+ const struct ovl_fh *fh,
+ int (*acceptable)(void *, struct dentry *))
+{
+ int bytes = (fh->len - offsetof(struct ovl_fh, fid));
+
+ /*
+ * When redirect_fh is disabled, 'invalid' file handles are stored
+ * to indicate that this entry has been copied up.
+ */
+ if (!bytes || (int)fh->type == FILEID_INVALID)
+ return ERR_PTR(-ESTALE);
+
+ /*
+ * Several layers can be on the same fs and decoded dentry may be in
+ * either one of those layers. We are looking for a match of dentry
+ * and mnt to find out to which layer the decoded dentry belongs to.
+ */
+ return exportfs_decode_fh(mnt, (struct fid *)fh->fid,
+ bytes >> 2, (int)fh->type,
+ acceptable, mnt);
+}
+
+static int ovl_acceptable(void *ctx, struct dentry *dentry)
+{
+ return 1;
+}
+
+/* Lookup by file handle in a lower layer mounted at @mnt */
+static int ovl_lookup_layer_fh(struct vfsmount *mnt, struct ovl_lookup_data *d,
+ struct dentry **ret)
+{
+ struct dentry *this = ovl_decode_fh(mnt, d->fh, ovl_acceptable);
+ int err;
+
+ if (IS_ERR(this)) {
+ err = PTR_ERR(this);
+ *ret = NULL;
+ if (err == -ESTALE)
+ return 0;
+ return err;
+ }
+
+ /* If found by file handle - don't follow that handle again */
+ ovl_reset_redirect_fh(d);
+ return ovl_lookup_data(this, d, 0, "", ret);
+}
+
+/* Find a lower layer where file handle should be decoded */
+static int ovl_find_layer_by_fh(struct dentry *dentry, int idx,
+ struct ovl_fh *fh)
+{
+ struct super_block *same_sb = ovl_same_sb(dentry->d_sb);
+
+ /* We only support redirect_fh when all layers are on the same fs */
+ if (!same_sb)
+ return -1;
+
+ /*
+ * Since all layers are on the same fs, we use the first layer for
+ * decoding the file handle. We may get a disconnected dentry,
+ * which is fine, because we only need to hold the origin inode in
+ * cache and use its inode number. We may even get a connected dentry,
+ * that is not under the first layer's root. That is also fine for
+ * using it's inode number - it's the same as if we held a reference
+ * to a dentry in first layer that was moved under us.
+ */
+ return 0;
+}
+
/*
* Returns next layer in stack starting from top.
* Returns -1 if this is the last layer.
@@ -270,7 +404,10 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
.stop = false,
.last = !poe->numlower,
.idx = 0,
+ .by_path = true,
.redirect = NULL,
+ .by_fh = ofs->redirect_fh,
+ .fh = NULL,
};
if (dentry->d_name.len > ofs->namelen)
@@ -299,7 +436,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
upperopaque = d.opaque;
}
- if (!d.stop && poe->numlower) {
+ if (!d.stop && (poe->numlower || d.fh)) {
err = -ENOMEM;
stack = kcalloc(ofs->numlower, sizeof(struct path),
GFP_TEMPORARY);
@@ -307,6 +444,33 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
goto out_put_upper;
}
+ /* Lookup non-dir copy up origin by file handle */
+ if (!d.stop && d.fh && !S_ISDIR(d.mode)) {
+ /* Find layer where file handle should be decoded */
+ i = ovl_find_layer_by_fh(dentry, 0, d.fh);
+ if (i < 0 || i > roe->numlower)
+ goto alloc_entry;
+
+ d.last = true;
+ d.by_path = false;
+ err = ovl_lookup_layer_fh(roe->lowerstack[i].mnt, &d, &this);
+ if (err)
+ goto out_put;
+
+ if (!this)
+ goto alloc_entry;
+
+ stack[ctr].dentry = this;
+ stack[ctr].mnt = roe->lowerstack[i].mnt;
+ ctr++;
+
+ /* Looked up by fh - do not lookup also by path */
+ goto alloc_entry;
+ }
+
+ /* Lookup lower layers by path */
+ d.by_path = true;
+ d.by_fh = false;
for (i = 0; !d.stop && i < poe->numlower; i++) {
struct path lowerpath = poe->lowerstack[i];
@@ -338,6 +502,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
}
}
+alloc_entry:
oe = ovl_alloc_entry(ctr);
err = -ENOMEM;
if (!oe)
@@ -386,6 +551,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
dput(upperdentry);
kfree(upperredirect);
out:
+ kfree(d.fh);
kfree(d.redirect);
revert_creds(old_cred);
return ERR_PTR(err);
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index da37aaf..90181e16 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -194,6 +194,7 @@ const char *ovl_dentry_get_redirect(struct dentry *dentry);
void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect);
bool ovl_redirect_fh(struct super_block *sb);
void ovl_clear_redirect_fh(struct super_block *sb);
+bool ovl_redirect_fh_ok(const char *redirect, size_t size);
void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry);
void ovl_inode_init(struct inode *inode, struct inode *realinode,
bool is_upper);
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 9db0588..08c55e6 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -236,6 +236,20 @@ void ovl_clear_redirect_fh(struct super_block *sb)
ofs->redirect_fh = false;
}
+bool ovl_redirect_fh_ok(const char *redirect, size_t size)
+{
+ struct ovl_fh *fh = (void *)redirect;
+
+ if (size < sizeof(struct ovl_fh) || size < fh->len)
+ return false;
+
+ if (fh->version > OVL_FH_VERSION ||
+ fh->magic != OVL_FH_MAGIC)
+ return false;
+
+ return true;
+}
+
void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
{
struct ovl_entry *oe = dentry->d_fsdata;
--
2.7.4
--
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