When a filesystem has internal mounts, it controls the filehandles
across all those mounts (subvols) in the filesystem. So it is useful to
be able to look up a filehandle again one mount, and get a result which
is in a different mount (part of the same overall file system).
This patch makes that possible by changing export_decode_fh() and
export_decode_fh_raw() to take a vfsmount pointer by reference, and
possibly change the vfsmount pointed to before returning.
The core of the change is in reconnect_path() which now not only checks
that the dentry is fully connected, but also that the vfsmnt reported
has the same 'dev' (reported by vfs_getattr) as the dentry.
If it doesn't, we walk up the dparent() chain to find the highest place
where the dev changes without there being a mount point, and trigger an
automount there.
As no filesystems yet provide local-mounts, this does not yet change any
behaviour.
In exportfs_decode_fh_raw() we previously tested for DCACHE_DISCONNECT
before calling reconnect_path(). That test is dropped. It was only a
minor optimisation and is now inconvenient.
The change in overlayfs needs more careful thought than I have yet given
it.
Signed-off-by: NeilBrown <neilb@xxxxxxx>
---
fs/exportfs/expfs.c | 100 +++++++++++++++++++++++++++++++++++++++-------
fs/fhandle.c | 2 -
fs/nfsd/nfsfh.c | 9 +++-
fs/overlayfs/namei.c | 5 ++
fs/xfs/xfs_ioctl.c | 12 ++++--
include/linux/exportfs.h | 4 +-
6 files changed, 106 insertions(+), 26 deletions(-)
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 0106eba46d5a..2d7c42137b49 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -207,11 +207,18 @@ static struct dentry *reconnect_one(struct vfsmount *mnt,
* that case reconnect_path may still succeed with target_dir fully
* connected, but further operations using the filehandle will fail when
* necessary (due to S_DEAD being set on the directory).
+ *
+ * If the filesystem supports multiple subvols, then *mntp may be updated
+ * to a subordinate mount point on the same filesystem.
*/
static int
-reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
+reconnect_path(struct vfsmount **mntp, struct dentry *target_dir, char *nbuf)
{
+ struct vfsmount *mnt = *mntp;
+ struct path path;
struct dentry *dentry, *parent;
+ struct kstat stat;
+ dev_t target_dev;
dentry = dget(target_dir);
@@ -232,6 +239,68 @@ reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf)
}
dput(dentry);
clear_disconnected(target_dir);
+
+ /* Need to find appropriate vfsmount, which might not exist yet.
+ * We may need to trigger automount points.
+ */
+ path.mnt = mnt;
+ path.dentry = target_dir;
+ vfs_getattr_nosec(&path, &stat, 0, AT_STATX_DONT_SYNC);
+ target_dev = stat.dev;
+
+ path.dentry = mnt->mnt_root;
+ vfs_getattr_nosec(&path, &stat, 0, AT_STATX_DONT_SYNC);
+
+ while (stat.dev != target_dev) {
+ /* walk up the dcache tree from target_dir, recording the
+ * location of the most recent change in dev number,
+ * until we find a mountpoint.
+ * If there was no change in show_dev result before the
+ * mountpount, the vfsmount at the mountpoint is what we want.
+ * If there was, we need to trigger an automount where the
+ * show_dev() result changed.
+ */
+ struct dentry *last_change = NULL;
+ dev_t last_dev = target_dev;
+
+ dentry = dget(target_dir);
+ while ((parent = dget_parent(dentry)) != dentry) {
+ path.dentry = parent;
+ vfs_getattr_nosec(&path, &stat, 0, AT_STATX_DONT_SYNC);
+ if (stat.dev != last_dev) {
+ path.dentry = dentry;
+ mnt = lookup_mnt(&path);
+ if (mnt) {
+ mntput(path.mnt);
+ path.mnt = mnt;
+ break;
+ }
+ dput(last_change);
+ last_change = dget(dentry);
+ last_dev = stat.dev;
+ }
+ dput(dentry);
+ dentry = parent;
+ }
+ dput(dentry); dput(parent);
+
+ if (!last_change)
+ break;
+
+ mnt = path.mnt;
+ path.dentry = last_change;
+ follow_down(&path, LOOKUP_AUTOMOUNT);
+ dput(path.dentry);
+ if (path.mnt == mnt)
+ /* There should have been a mount-trap there,
+ * but there wasn't. Just give up.
+ */
+ break;
+
+ path.dentry = mnt->mnt_root;
+ vfs_getattr_nosec(&path, &stat, 0, AT_STATX_DONT_SYNC);
+ }
+ *mntp = path.mnt;
return 0;
}
@@ -418,12 +487,13 @@ int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
EXPORT_SYMBOL_GPL(exportfs_encode_fh);
struct dentry *
-exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
+exportfs_decode_fh_raw(struct vfsmount **mntp, struct fid *fid, int fh_len,
int fileid_type,
int (*acceptable)(void *, struct dentry *),
void *context)
{
- const struct export_operations *nop = mnt->mnt_sb->s_export_op;
+ struct super_block *sb = (*mntp)->mnt_sb;
+ const struct export_operations *nop = sb->s_export_op;
struct dentry *result, *alias;
char nbuf[NAME_MAX+1];
int err;
@@ -433,7 +503,7 @@ exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
*/
if (!nop || !nop->fh_to_dentry)
return ERR_PTR(-ESTALE);
- result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
+ result = nop->fh_to_dentry(sb, fid, fh_len, fileid_type);
if (IS_ERR_OR_NULL(result))
return result;
@@ -452,14 +522,12 @@ exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
*
* On the positive side there is only one dentry for each
* directory inode. On the negative side this implies that we
- * to ensure our dentry is connected all the way up to the
+ * need to ensure our dentry is connected all the way up to the
* filesystem root.
*/
- if (result->d_flags & DCACHE_DISCONNECTED) {
- err = reconnect_path(mnt, result, nbuf);
- if (err)
- goto err_result;
- }
+ err = reconnect_path(mntp, result, nbuf);
+ if (err)
+ goto err_result;
if (!acceptable(context, result)) {
err = -EACCES;
@@ -494,7 +562,7 @@ exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
if (!nop->fh_to_parent)
goto err_result;
- target_dir = nop->fh_to_parent(mnt->mnt_sb, fid,
+ target_dir = nop->fh_to_parent(sb, fid,
fh_len, fileid_type);
if (!target_dir)
goto err_result;
@@ -507,7 +575,7 @@ exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
* connected to the filesystem root. The VFS really doesn't
* like disconnected directories..
*/
- err = reconnect_path(mnt, target_dir, nbuf);
+ err = reconnect_path(mntp, target_dir, nbuf);
if (err) {
dput(target_dir);
goto err_result;
@@ -518,7 +586,7 @@ exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
* dentry for the inode we're after, make sure that our
* inode is actually connected to the parent.
*/
- err = exportfs_get_name(mnt, target_dir, nbuf, result);
+ err = exportfs_get_name(*mntp, target_dir, nbuf, result);
if (err) {
dput(target_dir);
goto err_result;
@@ -556,7 +624,7 @@ exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
goto err_result;
}
- return alias;
+ return result;
}
err_result:
@@ -565,14 +633,14 @@ exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
}
EXPORT_SYMBOL_GPL(exportfs_decode_fh_raw);
-struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
+struct dentry *exportfs_decode_fh(struct vfsmount **mntp, struct fid *fid,
int fh_len, int fileid_type,
int (*acceptable)(void *, struct dentry *),
void *context)
{
struct dentry *ret;
- ret = exportfs_decode_fh_raw(mnt, fid, fh_len, fileid_type,
+ ret = exportfs_decode_fh_raw(mntp, fid, fh_len, fileid_type,
acceptable, context);
if (IS_ERR_OR_NULL(ret)) {
if (ret == ERR_PTR(-ENOMEM))
diff --git a/fs/fhandle.c b/fs/fhandle.c
index 6630c69c23a2..b47c7696469f 100644
--- a/fs/fhandle.c
+++ b/fs/fhandle.c
@@ -149,7 +149,7 @@ static int do_handle_to_path(int mountdirfd, struct file_handle *handle,
}
/* change the handle size to multiple of sizeof(u32) */
handle_dwords = handle->handle_bytes >> 2;
- path->dentry = exportfs_decode_fh(path->mnt,
+ path->dentry = exportfs_decode_fh(&path->mnt,
(struct fid *)handle->f_handle,
handle_dwords, handle->handle_type,
vfs_dentry_acceptable, NULL);
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 0bf7ac13ae50..4023046f63e2 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -157,6 +157,7 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
struct fid *fid = NULL, sfid;
struct svc_export *exp;
struct dentry *dentry;
+ struct vfsmount *mnt = NULL;
int fileid_type;
int data_left = fh->fh_size/4;
__be32 error;
@@ -253,6 +254,8 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
if (rqstp->rq_vers > 2)
error = nfserr_badhandle;
+ mnt = mntget(exp->ex_path.mnt);
+
if (fh->fh_version != 1) {
sfid.i32.ino = fh->ofh_ino;
sfid.i32.gen = fh->ofh_generation;
@@ -269,7 +272,7 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
if (fileid_type == FILEID_ROOT)
dentry = dget(exp->ex_path.dentry);
else {
- dentry = exportfs_decode_fh_raw(exp->ex_path.mnt, fid,
+ dentry = exportfs_decode_fh_raw(&mnt, fid,
data_left, fileid_type,
nfsd_acceptable, exp);
if (IS_ERR_OR_NULL(dentry)) {
@@ -299,7 +302,7 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
}
fhp->fh_dentry = dentry;
- fhp->fh_mnt = mntget(exp->ex_path.mnt);
+ fhp->fh_mnt = mnt;
fhp->fh_export = exp;
switch (rqstp->rq_vers) {
@@ -317,6 +320,7 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
return 0;
out:
+ mntput(mnt);
exp_put(exp);
return error;
}
@@ -428,7 +432,6 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type, int access)
return error;
}
-
/*
* Compose a file handle for an NFS reply.
*
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 210cd6f66e28..0bca19f6df54 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -155,6 +155,7 @@ struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh,
{
struct dentry *real;
int bytes;
+ struct vfsmount *mnt2;
if (!capable(CAP_DAC_READ_SEARCH))
return NULL;
@@ -169,9 +170,11 @@ struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh,
return NULL;
bytes = (fh->fb.len - offsetof(struct ovl_fb, fid));
- real = exportfs_decode_fh(mnt, (struct fid *)fh->fb.fid,
+ mnt2 = mntget(mnt);
+ real = exportfs_decode_fh(&mnt2, (struct fid *)fh->fb.fid,
bytes >> 2, (int)fh->fb.type,
connected ? ovl_acceptable : NULL, mnt);
+ mntput(mnt2);
if (IS_ERR(real)) {
/*
* Treat stale file handle to lower file as "origin unknown".
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 16039ea10ac9..76eb7d540811 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -149,6 +149,8 @@ xfs_handle_to_dentry(
{
xfs_handle_t handle;
struct xfs_fid64 fid;
+ struct dentry *ret;
+ struct vfsmount *mnt;
/*
* Only allow handle opens under a directory.
@@ -168,9 +170,13 @@ xfs_handle_to_dentry(
fid.ino = handle.ha_fid.fid_ino;
fid.gen = handle.ha_fid.fid_gen;
- return exportfs_decode_fh(parfilp->f_path.mnt, (struct fid *)&fid, 3,
- FILEID_INO32_GEN | XFS_FILEID_TYPE_64FLAG,
- xfs_handle_acceptable, NULL);
+ mnt = mntget(parfilp->f_path.mnt);
+ ret = exportfs_decode_fh(&mnt, (struct fid *)&fid, 3,
+ FILEID_INO32_GEN | XFS_FILEID_TYPE_64FLAG,
+ xfs_handle_acceptable, NULL);
+ WARN_ON(mnt != parfilp->f_path.mnt);
+ mntput(mnt);
+ return ret;
}
STATIC struct dentry *
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index fe848901fcc3..9a8c5434a5cf 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -228,12 +228,12 @@ extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
int *max_len, struct inode *parent);
extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
int *max_len, int connectable);
-extern struct dentry *exportfs_decode_fh_raw(struct vfsmount *mnt,
+extern struct dentry *exportfs_decode_fh_raw(struct vfsmount **mntp,
struct fid *fid, int fh_len,
int fileid_type,
int (*acceptable)(void *, struct dentry *),
void *context);
-extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
+extern struct dentry *exportfs_decode_fh(struct vfsmount **mnt, struct fid *fid,
int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
void *context);
