Commit a534c8d1 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Eric Van Hensbergen

fs/9p: Prevent parallel rename when doing fid_lookup

During fid lookup we need to make sure that the dentry->d_parent doesn't
change so that we can safely walk the parent dentries. To ensure that
we need to prevent cross directory rename during fid_lookup. Add a
per superblock rename_sem rw_semaphore to prevent parallel fid lookup and
rename.
Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatarVenkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: default avatarEric Van Hensbergen <ericvh@gmail.com>
parent ebf46264
...@@ -97,6 +97,34 @@ static struct p9_fid *v9fs_fid_find(struct dentry *dentry, u32 uid, int any) ...@@ -97,6 +97,34 @@ static struct p9_fid *v9fs_fid_find(struct dentry *dentry, u32 uid, int any)
return ret; return ret;
} }
/*
* We need to hold v9ses->rename_sem as long as we hold references
* to returned path array. Array element contain pointers to
* dentry names.
*/
static int build_path_from_dentry(struct v9fs_session_info *v9ses,
struct dentry *dentry, char ***names)
{
int n = 0, i;
char **wnames;
struct dentry *ds;
for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent)
n++;
wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL);
if (!wnames)
goto err_out;
for (ds = dentry, i = (n-1); i >= 0; i--, ds = ds->d_parent)
wnames[i] = (char *)ds->d_name.name;
*names = wnames;
return n;
err_out:
return -ENOMEM;
}
/** /**
* v9fs_fid_lookup - lookup for a fid, try to walk if not found * v9fs_fid_lookup - lookup for a fid, try to walk if not found
* @dentry: dentry to look for fid in * @dentry: dentry to look for fid in
...@@ -112,7 +140,7 @@ struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) ...@@ -112,7 +140,7 @@ struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
int i, n, l, clone, any, access; int i, n, l, clone, any, access;
u32 uid; u32 uid;
struct p9_fid *fid, *old_fid = NULL; struct p9_fid *fid, *old_fid = NULL;
struct dentry *d, *ds; struct dentry *ds;
struct v9fs_session_info *v9ses; struct v9fs_session_info *v9ses;
char **wnames, *uname; char **wnames, *uname;
...@@ -139,50 +167,62 @@ struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) ...@@ -139,50 +167,62 @@ struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
fid = v9fs_fid_find(dentry, uid, any); fid = v9fs_fid_find(dentry, uid, any);
if (fid) if (fid)
return fid; return fid;
/*
* we don't have a matching fid. To do a TWALK we need
* parent fid. We need to prevent rename when we want to
* look at the parent.
*/
down_read(&v9ses->rename_sem);
ds = dentry->d_parent; ds = dentry->d_parent;
fid = v9fs_fid_find(ds, uid, any); fid = v9fs_fid_find(ds, uid, any);
if (!fid) { /* walk from the root */ if (fid) {
n = 0; /* Found the parent fid do a lookup with that */
for (ds = dentry; !IS_ROOT(ds); ds = ds->d_parent) fid = p9_client_walk(fid, 1, (char **)&dentry->d_name.name, 1);
n++; goto fid_out;
}
up_read(&v9ses->rename_sem);
fid = v9fs_fid_find(ds, uid, any); /* start from the root and try to do a lookup */
if (!fid) { /* the user is not attached to the fs yet */ fid = v9fs_fid_find(dentry->d_sb->s_root, uid, any);
if (!fid) {
/* the user is not attached to the fs yet */
if (access == V9FS_ACCESS_SINGLE) if (access == V9FS_ACCESS_SINGLE)
return ERR_PTR(-EPERM); return ERR_PTR(-EPERM);
if (v9fs_proto_dotu(v9ses) || if (v9fs_proto_dotu(v9ses) || v9fs_proto_dotl(v9ses))
v9fs_proto_dotl(v9ses))
uname = NULL; uname = NULL;
else else
uname = v9ses->uname; uname = v9ses->uname;
fid = p9_client_attach(v9ses->clnt, NULL, uname, uid, fid = p9_client_attach(v9ses->clnt, NULL, uname, uid,
v9ses->aname); v9ses->aname);
if (IS_ERR(fid)) if (IS_ERR(fid))
return fid; return fid;
v9fs_fid_add(ds, fid); v9fs_fid_add(dentry->d_sb->s_root, fid);
} }
} else /* walk from the parent */ /* If we are root ourself just return that */
n = 1; if (dentry->d_sb->s_root == dentry)
if (ds == dentry)
return fid; return fid;
/*
wnames = kmalloc(sizeof(char *) * n, GFP_KERNEL); * Do a multipath walk with attached root.
if (!wnames) * When walking parent we need to make sure we
return ERR_PTR(-ENOMEM); * don't have a parallel rename happening
*/
for (d = dentry, i = (n-1); i >= 0; i--, d = d->d_parent) down_read(&v9ses->rename_sem);
wnames[i] = (char *) d->d_name.name; n = build_path_from_dentry(v9ses, dentry, &wnames);
if (n < 0) {
fid = ERR_PTR(n);
goto err_out;
}
clone = 1; clone = 1;
i = 0; i = 0;
while (i < n) { while (i < n) {
l = min(n - i, P9_MAXWELEM); l = min(n - i, P9_MAXWELEM);
/*
* We need to hold rename lock when doing a multipath
* walk to ensure none of the patch component change
*/
fid = p9_client_walk(fid, l, &wnames[i], clone); fid = p9_client_walk(fid, l, &wnames[i], clone);
if (IS_ERR(fid)) { if (IS_ERR(fid)) {
if (old_fid) { if (old_fid) {
...@@ -194,15 +234,17 @@ struct p9_fid *v9fs_fid_lookup(struct dentry *dentry) ...@@ -194,15 +234,17 @@ struct p9_fid *v9fs_fid_lookup(struct dentry *dentry)
p9_client_clunk(old_fid); p9_client_clunk(old_fid);
} }
kfree(wnames); kfree(wnames);
return fid; goto err_out;
} }
old_fid = fid; old_fid = fid;
i += l; i += l;
clone = 0; clone = 0;
} }
kfree(wnames); kfree(wnames);
fid_out:
v9fs_fid_add(dentry, fid); v9fs_fid_add(dentry, fid);
err_out:
up_read(&v9ses->rename_sem);
return fid; return fid;
} }
......
...@@ -237,6 +237,7 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses, ...@@ -237,6 +237,7 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses,
__putname(v9ses->uname); __putname(v9ses->uname);
return ERR_PTR(-ENOMEM); return ERR_PTR(-ENOMEM);
} }
init_rwsem(&v9ses->rename_sem);
rc = bdi_setup_and_register(&v9ses->bdi, "9p", BDI_CAP_MAP_COPY); rc = bdi_setup_and_register(&v9ses->bdi, "9p", BDI_CAP_MAP_COPY);
if (rc) { if (rc) {
......
...@@ -104,6 +104,7 @@ struct v9fs_session_info { ...@@ -104,6 +104,7 @@ struct v9fs_session_info {
struct p9_client *clnt; /* 9p client */ struct p9_client *clnt; /* 9p client */
struct list_head slist; /* list of sessions registered with v9fs */ struct list_head slist; /* list of sessions registered with v9fs */
struct backing_dev_info bdi; struct backing_dev_info bdi;
struct rw_semaphore rename_sem;
}; };
struct p9_fid *v9fs_session_init(struct v9fs_session_info *, const char *, struct p9_fid *v9fs_session_init(struct v9fs_session_info *, const char *,
......
...@@ -948,6 +948,7 @@ static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry, ...@@ -948,6 +948,7 @@ static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
sb = dir->i_sb; sb = dir->i_sb;
v9ses = v9fs_inode2v9ses(dir); v9ses = v9fs_inode2v9ses(dir);
/* We can walk d_parent because we hold the dir->i_mutex */
dfid = v9fs_fid_lookup(dentry->d_parent); dfid = v9fs_fid_lookup(dentry->d_parent);
if (IS_ERR(dfid)) if (IS_ERR(dfid))
return ERR_CAST(dfid); return ERR_CAST(dfid);
...@@ -1055,27 +1056,33 @@ v9fs_vfs_rename(struct inode *old_dir, struct dentry *old_dentry, ...@@ -1055,27 +1056,33 @@ v9fs_vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
goto clunk_olddir; goto clunk_olddir;
} }
down_write(&v9ses->rename_sem);
if (v9fs_proto_dotl(v9ses)) { if (v9fs_proto_dotl(v9ses)) {
retval = p9_client_rename(oldfid, newdirfid, retval = p9_client_rename(oldfid, newdirfid,
(char *) new_dentry->d_name.name); (char *) new_dentry->d_name.name);
if (retval != -ENOSYS) if (retval != -ENOSYS)
goto clunk_newdir; goto clunk_newdir;
} }
if (old_dentry->d_parent != new_dentry->d_parent) {
/*
* 9P .u can only handle file rename in the same directory
*/
/* 9P can only handle file rename in the same directory */
if (memcmp(&olddirfid->qid, &newdirfid->qid, sizeof(newdirfid->qid))) {
P9_DPRINTK(P9_DEBUG_ERROR, P9_DPRINTK(P9_DEBUG_ERROR,
"old dir and new dir are different\n"); "old dir and new dir are different\n");
retval = -EXDEV; retval = -EXDEV;
goto clunk_newdir; goto clunk_newdir;
} }
v9fs_blank_wstat(&wstat); v9fs_blank_wstat(&wstat);
wstat.muid = v9ses->uname; wstat.muid = v9ses->uname;
wstat.name = (char *) new_dentry->d_name.name; wstat.name = (char *) new_dentry->d_name.name;
retval = p9_client_wstat(oldfid, &wstat); retval = p9_client_wstat(oldfid, &wstat);
clunk_newdir: clunk_newdir:
if (!retval)
/* successful rename */
d_move(old_dentry, new_dentry);
up_write(&v9ses->rename_sem);
p9_client_clunk(newdirfid); p9_client_clunk(newdirfid);
clunk_olddir: clunk_olddir:
......
...@@ -287,4 +287,5 @@ struct file_system_type v9fs_fs_type = { ...@@ -287,4 +287,5 @@ struct file_system_type v9fs_fs_type = {
.get_sb = v9fs_get_sb, .get_sb = v9fs_get_sb,
.kill_sb = v9fs_kill_super, .kill_sb = v9fs_kill_super,
.owner = THIS_MODULE, .owner = THIS_MODULE,
.fs_flags = FS_RENAME_DOES_D_MOVE,
}; };
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