v4.19.13 snapshot.
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
new file mode 100644
index 0000000..54e5d17
--- /dev/null
+++ b/fs/overlayfs/export.c
@@ -0,0 +1,851 @@
+/*
+ * Overlayfs NFS export support.
+ *
+ * Amir Goldstein <amir73il@gmail.com>
+ *
+ * Copyright (C) 2017-2018 CTERA Networks. All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/cred.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/xattr.h>
+#include <linux/exportfs.h>
+#include <linux/ratelimit.h>
+#include "overlayfs.h"
+
+static int ovl_encode_maybe_copy_up(struct dentry *dentry)
+{
+ int err;
+
+ if (ovl_dentry_upper(dentry))
+ return 0;
+
+ err = ovl_want_write(dentry);
+ if (!err) {
+ err = ovl_copy_up(dentry);
+ ovl_drop_write(dentry);
+ }
+
+ if (err) {
+ pr_warn_ratelimited("overlayfs: failed to copy up on encode (%pd2, err=%i)\n",
+ dentry, err);
+ }
+
+ return err;
+}
+
+/*
+ * Before encoding a non-upper directory file handle from real layer N, we need
+ * to check if it will be possible to reconnect an overlay dentry from the real
+ * lower decoded dentry. This is done by following the overlay ancestry up to a
+ * "layer N connected" ancestor and verifying that all parents along the way are
+ * "layer N connectable". If an ancestor that is NOT "layer N connectable" is
+ * found, we need to copy up an ancestor, which is "layer N connectable", thus
+ * making that ancestor "layer N connected". For example:
+ *
+ * layer 1: /a
+ * layer 2: /a/b/c
+ *
+ * The overlay dentry /a is NOT "layer 2 connectable", because if dir /a is
+ * copied up and renamed, upper dir /a will be indexed by lower dir /a from
+ * layer 1. The dir /a from layer 2 will never be indexed, so the algorithm (*)
+ * in ovl_lookup_real_ancestor() will not be able to lookup a connected overlay
+ * dentry from the connected lower dentry /a/b/c.
+ *
+ * To avoid this problem on decode time, we need to copy up an ancestor of
+ * /a/b/c, which is "layer 2 connectable", on encode time. That ancestor is
+ * /a/b. After copy up (and index) of /a/b, it will become "layer 2 connected"
+ * and when the time comes to decode the file handle from lower dentry /a/b/c,
+ * ovl_lookup_real_ancestor() will find the indexed ancestor /a/b and decoding
+ * a connected overlay dentry will be accomplished.
+ *
+ * (*) the algorithm in ovl_lookup_real_ancestor() can be improved to lookup an
+ * entry /a in the lower layers above layer N and find the indexed dir /a from
+ * layer 1. If that improvement is made, then the check for "layer N connected"
+ * will need to verify there are no redirects in lower layers above N. In the
+ * example above, /a will be "layer 2 connectable". However, if layer 2 dir /a
+ * is a target of a layer 1 redirect, then /a will NOT be "layer 2 connectable":
+ *
+ * layer 1: /A (redirect = /a)
+ * layer 2: /a/b/c
+ */
+
+/* Return the lowest layer for encoding a connectable file handle */
+static int ovl_connectable_layer(struct dentry *dentry)
+{
+ struct ovl_entry *oe = OVL_E(dentry);
+
+ /* We can get overlay root from root of any layer */
+ if (dentry == dentry->d_sb->s_root)
+ return oe->numlower;
+
+ /*
+ * If it's an unindexed merge dir, then it's not connectable with any
+ * lower layer
+ */
+ if (ovl_dentry_upper(dentry) &&
+ !ovl_test_flag(OVL_INDEX, d_inode(dentry)))
+ return 0;
+
+ /* We can get upper/overlay path from indexed/lower dentry */
+ return oe->lowerstack[0].layer->idx;
+}
+
+/*
+ * @dentry is "connected" if all ancestors up to root or a "connected" ancestor
+ * have the same uppermost lower layer as the origin's layer. We may need to
+ * copy up a "connectable" ancestor to make it "connected". A "connected" dentry
+ * cannot become non "connected", so cache positive result in dentry flags.
+ *
+ * Return the connected origin layer or < 0 on error.
+ */
+static int ovl_connect_layer(struct dentry *dentry)
+{
+ struct dentry *next, *parent = NULL;
+ int origin_layer;
+ int err = 0;
+
+ if (WARN_ON(dentry == dentry->d_sb->s_root) ||
+ WARN_ON(!ovl_dentry_lower(dentry)))
+ return -EIO;
+
+ origin_layer = OVL_E(dentry)->lowerstack[0].layer->idx;
+ if (ovl_dentry_test_flag(OVL_E_CONNECTED, dentry))
+ return origin_layer;
+
+ /* Find the topmost origin layer connectable ancestor of @dentry */
+ next = dget(dentry);
+ for (;;) {
+ parent = dget_parent(next);
+ if (WARN_ON(parent == next)) {
+ err = -EIO;
+ break;
+ }
+
+ /*
+ * If @parent is not origin layer connectable, then copy up
+ * @next which is origin layer connectable and we are done.
+ */
+ if (ovl_connectable_layer(parent) < origin_layer) {
+ err = ovl_encode_maybe_copy_up(next);
+ break;
+ }
+
+ /* If @parent is connected or indexed we are done */
+ if (ovl_dentry_test_flag(OVL_E_CONNECTED, parent) ||
+ ovl_test_flag(OVL_INDEX, d_inode(parent)))
+ break;
+
+ dput(next);
+ next = parent;
+ }
+
+ dput(parent);
+ dput(next);
+
+ if (!err)
+ ovl_dentry_set_flag(OVL_E_CONNECTED, dentry);
+
+ return err ?: origin_layer;
+}
+
+/*
+ * We only need to encode origin if there is a chance that the same object was
+ * encoded pre copy up and then we need to stay consistent with the same
+ * encoding also after copy up. If non-pure upper is not indexed, then it was
+ * copied up before NFS export was enabled. In that case we don't need to worry
+ * about staying consistent with pre copy up encoding and we encode an upper
+ * file handle. Overlay root dentry is a private case of non-indexed upper.
+ *
+ * The following table summarizes the different file handle encodings used for
+ * different overlay object types:
+ *
+ * Object type | Encoding
+ * --------------------------------
+ * Pure upper | U
+ * Non-indexed upper | U
+ * Indexed upper | L (*)
+ * Non-upper | L (*)
+ *
+ * U = upper file handle
+ * L = lower file handle
+ *
+ * (*) Connecting an overlay dir from real lower dentry is not always
+ * possible when there are redirects in lower layers and non-indexed merge dirs.
+ * To mitigate those case, we may copy up the lower dir ancestor before encode
+ * a lower dir file handle.
+ *
+ * Return 0 for upper file handle, > 0 for lower file handle or < 0 on error.
+ */
+static int ovl_check_encode_origin(struct dentry *dentry)
+{
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+
+ /* Upper file handle for pure upper */
+ if (!ovl_dentry_lower(dentry))
+ return 0;
+
+ /*
+ * Upper file handle for non-indexed upper.
+ *
+ * Root is never indexed, so if there's an upper layer, encode upper for
+ * root.
+ */
+ if (ovl_dentry_upper(dentry) &&
+ !ovl_test_flag(OVL_INDEX, d_inode(dentry)))
+ return 0;
+
+ /*
+ * Decoding a merge dir, whose origin's ancestor is under a redirected
+ * lower dir or under a non-indexed upper is not always possible.
+ * ovl_connect_layer() will try to make origin's layer "connected" by
+ * copying up a "connectable" ancestor.
+ */
+ if (d_is_dir(dentry) && ofs->upper_mnt)
+ return ovl_connect_layer(dentry);
+
+ /* Lower file handle for indexed and non-upper dir/non-dir */
+ return 1;
+}
+
+static int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen)
+{
+ struct ovl_fh *fh = NULL;
+ int err, enc_lower;
+
+ /*
+ * Check if we should encode a lower or upper file handle and maybe
+ * copy up an ancestor to make lower file handle connectable.
+ */
+ err = enc_lower = ovl_check_encode_origin(dentry);
+ if (enc_lower < 0)
+ goto fail;
+
+ /* Encode an upper or lower file handle */
+ fh = ovl_encode_real_fh(enc_lower ? ovl_dentry_lower(dentry) :
+ ovl_dentry_upper(dentry), !enc_lower);
+ err = PTR_ERR(fh);
+ if (IS_ERR(fh))
+ goto fail;
+
+ err = -EOVERFLOW;
+ if (fh->len > buflen)
+ goto fail;
+
+ memcpy(buf, (char *)fh, fh->len);
+ err = fh->len;
+
+out:
+ kfree(fh);
+ return err;
+
+fail:
+ pr_warn_ratelimited("overlayfs: failed to encode file handle (%pd2, err=%i, buflen=%d, len=%d, type=%d)\n",
+ dentry, err, buflen, fh ? (int)fh->len : 0,
+ fh ? fh->type : 0);
+ goto out;
+}
+
+static int ovl_dentry_to_fh(struct dentry *dentry, u32 *fid, int *max_len)
+{
+ int res, len = *max_len << 2;
+
+ res = ovl_d_to_fh(dentry, (char *)fid, len);
+ if (res <= 0)
+ return FILEID_INVALID;
+
+ len = res;
+
+ /* Round up to dwords */
+ *max_len = (len + 3) >> 2;
+ return OVL_FILEID;
+}
+
+static int ovl_encode_fh(struct inode *inode, u32 *fid, int *max_len,
+ struct inode *parent)
+{
+ struct dentry *dentry;
+ int type;
+
+ /* TODO: encode connectable file handles */
+ if (parent)
+ return FILEID_INVALID;
+
+ dentry = d_find_any_alias(inode);
+ if (WARN_ON(!dentry))
+ return FILEID_INVALID;
+
+ type = ovl_dentry_to_fh(dentry, fid, max_len);
+
+ dput(dentry);
+ return type;
+}
+
+/*
+ * Find or instantiate an overlay dentry from real dentries and index.
+ */
+static struct dentry *ovl_obtain_alias(struct super_block *sb,
+ struct dentry *upper_alias,
+ struct ovl_path *lowerpath,
+ struct dentry *index)
+{
+ struct dentry *lower = lowerpath ? lowerpath->dentry : NULL;
+ struct dentry *upper = upper_alias ?: index;
+ struct dentry *dentry;
+ struct inode *inode;
+ struct ovl_entry *oe;
+ struct ovl_inode_params oip = {
+ .lowerpath = lowerpath,
+ .index = index,
+ .numlower = !!lower
+ };
+
+ /* We get overlay directory dentries with ovl_lookup_real() */
+ if (d_is_dir(upper ?: lower))
+ return ERR_PTR(-EIO);
+
+ oip.upperdentry = dget(upper);
+ inode = ovl_get_inode(sb, &oip);
+ if (IS_ERR(inode)) {
+ dput(upper);
+ return ERR_CAST(inode);
+ }
+
+ if (upper)
+ ovl_set_flag(OVL_UPPERDATA, inode);
+
+ dentry = d_find_any_alias(inode);
+ if (!dentry) {
+ dentry = d_alloc_anon(inode->i_sb);
+ if (!dentry)
+ goto nomem;
+ oe = ovl_alloc_entry(lower ? 1 : 0);
+ if (!oe)
+ goto nomem;
+
+ if (lower) {
+ oe->lowerstack->dentry = dget(lower);
+ oe->lowerstack->layer = lowerpath->layer;
+ }
+ dentry->d_fsdata = oe;
+ if (upper_alias)
+ ovl_dentry_set_upper_alias(dentry);
+ }
+
+ return d_instantiate_anon(dentry, inode);
+
+nomem:
+ iput(inode);
+ dput(dentry);
+ return ERR_PTR(-ENOMEM);
+}
+
+/* Get the upper or lower dentry in stach whose on layer @idx */
+static struct dentry *ovl_dentry_real_at(struct dentry *dentry, int idx)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+ int i;
+
+ if (!idx)
+ return ovl_dentry_upper(dentry);
+
+ for (i = 0; i < oe->numlower; i++) {
+ if (oe->lowerstack[i].layer->idx == idx)
+ return oe->lowerstack[i].dentry;
+ }
+
+ return NULL;
+}
+
+/*
+ * Lookup a child overlay dentry to get a connected overlay dentry whose real
+ * dentry is @real. If @real is on upper layer, we lookup a child overlay
+ * dentry with the same name as the real dentry. Otherwise, we need to consult
+ * index for lookup.
+ */
+static struct dentry *ovl_lookup_real_one(struct dentry *connected,
+ struct dentry *real,
+ struct ovl_layer *layer)
+{
+ struct inode *dir = d_inode(connected);
+ struct dentry *this, *parent = NULL;
+ struct name_snapshot name;
+ int err;
+
+ /*
+ * Lookup child overlay dentry by real name. The dir mutex protects us
+ * from racing with overlay rename. If the overlay dentry that is above
+ * real has already been moved to a parent that is not under the
+ * connected overlay dir, we return -ECHILD and restart the lookup of
+ * connected real path from the top.
+ */
+ inode_lock_nested(dir, I_MUTEX_PARENT);
+ err = -ECHILD;
+ parent = dget_parent(real);
+ if (ovl_dentry_real_at(connected, layer->idx) != parent)
+ goto fail;
+
+ /*
+ * We also need to take a snapshot of real dentry name to protect us
+ * from racing with underlying layer rename. In this case, we don't
+ * care about returning ESTALE, only from dereferencing a free name
+ * pointer because we hold no lock on the real dentry.
+ */
+ take_dentry_name_snapshot(&name, real);
+ this = lookup_one_len(name.name, connected, strlen(name.name));
+ err = PTR_ERR(this);
+ if (IS_ERR(this)) {
+ goto fail;
+ } else if (!this || !this->d_inode) {
+ dput(this);
+ err = -ENOENT;
+ goto fail;
+ } else if (ovl_dentry_real_at(this, layer->idx) != real) {
+ dput(this);
+ err = -ESTALE;
+ goto fail;
+ }
+
+out:
+ release_dentry_name_snapshot(&name);
+ dput(parent);
+ inode_unlock(dir);
+ return this;
+
+fail:
+ pr_warn_ratelimited("overlayfs: failed to lookup one by real (%pd2, layer=%d, connected=%pd2, err=%i)\n",
+ real, layer->idx, connected, err);
+ this = ERR_PTR(err);
+ goto out;
+}
+
+static struct dentry *ovl_lookup_real(struct super_block *sb,
+ struct dentry *real,
+ struct ovl_layer *layer);
+
+/*
+ * Lookup an indexed or hashed overlay dentry by real inode.
+ */
+static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
+ struct dentry *real,
+ struct ovl_layer *layer)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+ struct ovl_layer upper_layer = { .mnt = ofs->upper_mnt };
+ struct dentry *index = NULL;
+ struct dentry *this = NULL;
+ struct inode *inode;
+
+ /*
+ * Decoding upper dir from index is expensive, so first try to lookup
+ * overlay dentry in inode/dcache.
+ */
+ inode = ovl_lookup_inode(sb, real, !layer->idx);
+ if (IS_ERR(inode))
+ return ERR_CAST(inode);
+ if (inode) {
+ this = d_find_any_alias(inode);
+ iput(inode);
+ }
+
+ /*
+ * For decoded lower dir file handle, lookup index by origin to check
+ * if lower dir was copied up and and/or removed.
+ */
+ if (!this && layer->idx && ofs->indexdir && !WARN_ON(!d_is_dir(real))) {
+ index = ovl_lookup_index(ofs, NULL, real, false);
+ if (IS_ERR(index))
+ return index;
+ }
+
+ /* Get connected upper overlay dir from index */
+ if (index) {
+ struct dentry *upper = ovl_index_upper(ofs, index);
+
+ dput(index);
+ if (IS_ERR_OR_NULL(upper))
+ return upper;
+
+ /*
+ * ovl_lookup_real() in lower layer may call recursively once to
+ * ovl_lookup_real() in upper layer. The first level call walks
+ * back lower parents to the topmost indexed parent. The second
+ * recursive call walks back from indexed upper to the topmost
+ * connected/hashed upper parent (or up to root).
+ */
+ this = ovl_lookup_real(sb, upper, &upper_layer);
+ dput(upper);
+ }
+
+ if (IS_ERR_OR_NULL(this))
+ return this;
+
+ if (WARN_ON(ovl_dentry_real_at(this, layer->idx) != real)) {
+ dput(this);
+ this = ERR_PTR(-EIO);
+ }
+
+ return this;
+}
+
+/*
+ * Lookup an indexed or hashed overlay dentry, whose real dentry is an
+ * ancestor of @real.
+ */
+static struct dentry *ovl_lookup_real_ancestor(struct super_block *sb,
+ struct dentry *real,
+ struct ovl_layer *layer)
+{
+ struct dentry *next, *parent = NULL;
+ struct dentry *ancestor = ERR_PTR(-EIO);
+
+ if (real == layer->mnt->mnt_root)
+ return dget(sb->s_root);
+
+ /* Find the topmost indexed or hashed ancestor */
+ next = dget(real);
+ for (;;) {
+ parent = dget_parent(next);
+
+ /*
+ * Lookup a matching overlay dentry in inode/dentry
+ * cache or in index by real inode.
+ */
+ ancestor = ovl_lookup_real_inode(sb, next, layer);
+ if (ancestor)
+ break;
+
+ if (parent == layer->mnt->mnt_root) {
+ ancestor = dget(sb->s_root);
+ break;
+ }
+
+ /*
+ * If @real has been moved out of the layer root directory,
+ * we will eventully hit the real fs root. This cannot happen
+ * by legit overlay rename, so we return error in that case.
+ */
+ if (parent == next) {
+ ancestor = ERR_PTR(-EXDEV);
+ break;
+ }
+
+ dput(next);
+ next = parent;
+ }
+
+ dput(parent);
+ dput(next);
+
+ return ancestor;
+}
+
+/*
+ * Lookup a connected overlay dentry whose real dentry is @real.
+ * If @real is on upper layer, we lookup a child overlay dentry with the same
+ * path the real dentry. Otherwise, we need to consult index for lookup.
+ */
+static struct dentry *ovl_lookup_real(struct super_block *sb,
+ struct dentry *real,
+ struct ovl_layer *layer)
+{
+ struct dentry *connected;
+ int err = 0;
+
+ connected = ovl_lookup_real_ancestor(sb, real, layer);
+ if (IS_ERR(connected))
+ return connected;
+
+ while (!err) {
+ struct dentry *next, *this;
+ struct dentry *parent = NULL;
+ struct dentry *real_connected = ovl_dentry_real_at(connected,
+ layer->idx);
+
+ if (real_connected == real)
+ break;
+
+ /* Find the topmost dentry not yet connected */
+ next = dget(real);
+ for (;;) {
+ parent = dget_parent(next);
+
+ if (parent == real_connected)
+ break;
+
+ /*
+ * If real has been moved out of 'real_connected',
+ * we will not find 'real_connected' and hit the layer
+ * root. In that case, we need to restart connecting.
+ * This game can go on forever in the worst case. We
+ * may want to consider taking s_vfs_rename_mutex if
+ * this happens more than once.
+ */
+ if (parent == layer->mnt->mnt_root) {
+ dput(connected);
+ connected = dget(sb->s_root);
+ break;
+ }
+
+ /*
+ * If real file has been moved out of the layer root
+ * directory, we will eventully hit the real fs root.
+ * This cannot happen by legit overlay rename, so we
+ * return error in that case.
+ */
+ if (parent == next) {
+ err = -EXDEV;
+ break;
+ }
+
+ dput(next);
+ next = parent;
+ }
+
+ if (!err) {
+ this = ovl_lookup_real_one(connected, next, layer);
+ if (IS_ERR(this))
+ err = PTR_ERR(this);
+
+ /*
+ * Lookup of child in overlay can fail when racing with
+ * overlay rename of child away from 'connected' parent.
+ * In this case, we need to restart the lookup from the
+ * top, because we cannot trust that 'real_connected' is
+ * still an ancestor of 'real'. There is a good chance
+ * that the renamed overlay ancestor is now in cache, so
+ * ovl_lookup_real_ancestor() will find it and we can
+ * continue to connect exactly from where lookup failed.
+ */
+ if (err == -ECHILD) {
+ this = ovl_lookup_real_ancestor(sb, real,
+ layer);
+ err = PTR_ERR_OR_ZERO(this);
+ }
+ if (!err) {
+ dput(connected);
+ connected = this;
+ }
+ }
+
+ dput(parent);
+ dput(next);
+ }
+
+ if (err)
+ goto fail;
+
+ return connected;
+
+fail:
+ pr_warn_ratelimited("overlayfs: failed to lookup by real (%pd2, layer=%d, connected=%pd2, err=%i)\n",
+ real, layer->idx, connected, err);
+ dput(connected);
+ return ERR_PTR(err);
+}
+
+/*
+ * Get an overlay dentry from upper/lower real dentries and index.
+ */
+static struct dentry *ovl_get_dentry(struct super_block *sb,
+ struct dentry *upper,
+ struct ovl_path *lowerpath,
+ struct dentry *index)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+ struct ovl_layer upper_layer = { .mnt = ofs->upper_mnt };
+ struct ovl_layer *layer = upper ? &upper_layer : lowerpath->layer;
+ struct dentry *real = upper ?: (index ?: lowerpath->dentry);
+
+ /*
+ * Obtain a disconnected overlay dentry from a non-dir real dentry
+ * and index.
+ */
+ if (!d_is_dir(real))
+ return ovl_obtain_alias(sb, upper, lowerpath, index);
+
+ /* Removed empty directory? */
+ if ((real->d_flags & DCACHE_DISCONNECTED) || d_unhashed(real))
+ return ERR_PTR(-ENOENT);
+
+ /*
+ * If real dentry is connected and hashed, get a connected overlay
+ * dentry whose real dentry is @real.
+ */
+ return ovl_lookup_real(sb, real, layer);
+}
+
+static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
+ struct ovl_fh *fh)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+ struct dentry *dentry;
+ struct dentry *upper;
+
+ if (!ofs->upper_mnt)
+ return ERR_PTR(-EACCES);
+
+ upper = ovl_decode_real_fh(fh, ofs->upper_mnt, true);
+ if (IS_ERR_OR_NULL(upper))
+ return upper;
+
+ dentry = ovl_get_dentry(sb, upper, NULL, NULL);
+ dput(upper);
+
+ return dentry;
+}
+
+static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
+ struct ovl_fh *fh)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+ struct ovl_path origin = { };
+ struct ovl_path *stack = &origin;
+ struct dentry *dentry = NULL;
+ struct dentry *index = NULL;
+ struct inode *inode;
+ int err;
+
+ /* First lookup overlay inode in inode cache by origin fh */
+ err = ovl_check_origin_fh(ofs, fh, false, NULL, &stack);
+ if (err)
+ return ERR_PTR(err);
+
+ if (!d_is_dir(origin.dentry) ||
+ !(origin.dentry->d_flags & DCACHE_DISCONNECTED)) {
+ inode = ovl_lookup_inode(sb, origin.dentry, false);
+ err = PTR_ERR(inode);
+ if (IS_ERR(inode))
+ goto out_err;
+ if (inode) {
+ dentry = d_find_any_alias(inode);
+ iput(inode);
+ if (dentry)
+ goto out;
+ }
+ }
+
+ /* Then lookup indexed upper/whiteout by origin fh */
+ if (ofs->indexdir) {
+ index = ovl_get_index_fh(ofs, fh);
+ err = PTR_ERR(index);
+ if (IS_ERR(index)) {
+ index = NULL;
+ goto out_err;
+ }
+ }
+
+ /* Then try to get a connected upper dir by index */
+ if (index && d_is_dir(index)) {
+ struct dentry *upper = ovl_index_upper(ofs, index);
+
+ err = PTR_ERR(upper);
+ if (IS_ERR_OR_NULL(upper))
+ goto out_err;
+
+ dentry = ovl_get_dentry(sb, upper, NULL, NULL);
+ dput(upper);
+ goto out;
+ }
+
+ /* Find origin.dentry again with ovl_acceptable() layer check */
+ if (d_is_dir(origin.dentry)) {
+ dput(origin.dentry);
+ origin.dentry = NULL;
+ err = ovl_check_origin_fh(ofs, fh, true, NULL, &stack);
+ if (err)
+ goto out_err;
+ }
+ if (index) {
+ err = ovl_verify_origin(index, origin.dentry, false);
+ if (err)
+ goto out_err;
+ }
+
+ /* Get a connected non-upper dir or disconnected non-dir */
+ dentry = ovl_get_dentry(sb, NULL, &origin, index);
+
+out:
+ dput(origin.dentry);
+ dput(index);
+ return dentry;
+
+out_err:
+ dentry = ERR_PTR(err);
+ goto out;
+}
+
+static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid,
+ int fh_len, int fh_type)
+{
+ struct dentry *dentry = NULL;
+ struct ovl_fh *fh = (struct ovl_fh *) fid;
+ int len = fh_len << 2;
+ unsigned int flags = 0;
+ int err;
+
+ err = -EINVAL;
+ if (fh_type != OVL_FILEID)
+ goto out_err;
+
+ err = ovl_check_fh_len(fh, len);
+ if (err)
+ goto out_err;
+
+ flags = fh->flags;
+ dentry = (flags & OVL_FH_FLAG_PATH_UPPER) ?
+ ovl_upper_fh_to_d(sb, fh) :
+ ovl_lower_fh_to_d(sb, fh);
+ err = PTR_ERR(dentry);
+ if (IS_ERR(dentry) && err != -ESTALE)
+ goto out_err;
+
+ return dentry;
+
+out_err:
+ pr_warn_ratelimited("overlayfs: failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n",
+ len, fh_type, flags, err);
+ return ERR_PTR(err);
+}
+
+static struct dentry *ovl_fh_to_parent(struct super_block *sb, struct fid *fid,
+ int fh_len, int fh_type)
+{
+ pr_warn_ratelimited("overlayfs: connectable file handles not supported; use 'no_subtree_check' exportfs option.\n");
+ return ERR_PTR(-EACCES);
+}
+
+static int ovl_get_name(struct dentry *parent, char *name,
+ struct dentry *child)
+{
+ /*
+ * ovl_fh_to_dentry() returns connected dir overlay dentries and
+ * ovl_fh_to_parent() is not implemented, so we should not get here.
+ */
+ WARN_ON_ONCE(1);
+ return -EIO;
+}
+
+static struct dentry *ovl_get_parent(struct dentry *dentry)
+{
+ /*
+ * ovl_fh_to_dentry() returns connected dir overlay dentries, so we
+ * should not get here.
+ */
+ WARN_ON_ONCE(1);
+ return ERR_PTR(-EIO);
+}
+
+const struct export_operations ovl_export_operations = {
+ .encode_fh = ovl_encode_fh,
+ .fh_to_dentry = ovl_fh_to_dentry,
+ .fh_to_parent = ovl_fh_to_parent,
+ .get_name = ovl_get_name,
+ .get_parent = ovl_get_parent,
+};