start_creating() is similar to simple_start_creating() but is not so
simple.
It takes a qstr for the name, includes permission checking, and does NOT
report an error if the name already exists, returning a positive dentry
instead.
This is currently used by nfsd and cachefiles. Overlayfs might have a
use for it too.
end_creating() is called after the dentry has been used. Unlike
simple_end_creating(), end_creating() drop the reference to the dentry
as it is generally no longer needed. This is exactly end_dirop_mkdir(),
but using that everywhere looks a bit odd...
These calls help encapsulate locking rules so that directory locking can
be changed.
Signed-off-by: NeilBrown <neil@xxxxxxxxxx>
---
fs/cachefiles/namei.c | 33 +++++++++++++++------------------
fs/namei.c | 25 +++++++++++++++++++++++++
fs/nfsd/nfs3proc.c | 14 +++++---------
fs/nfsd/nfs4proc.c | 14 +++++---------
fs/nfsd/nfs4recover.c | 16 ++++++----------
fs/nfsd/nfsproc.c | 11 +++++------
fs/nfsd/vfs.c | 42 +++++++++++++++---------------------------
include/linux/namei.h | 18 ++++++++++++++++++
8 files changed, 94 insertions(+), 79 deletions(-)
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index d1edb2ac3837..9af324473967 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -93,12 +93,11 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
_enter(",,%s", dirname);
/* search the current directory for the element name */
- inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);
retry:
ret = cachefiles_inject_read_error();
if (ret == 0)
- subdir = lookup_one(&nop_mnt_idmap, &QSTR(dirname), dir);
+ subdir = start_creating(&nop_mnt_idmap, dir, &QSTR(dirname));
else
subdir = ERR_PTR(ret);
trace_cachefiles_lookup(NULL, dir, subdir);
@@ -141,7 +140,7 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
trace_cachefiles_mkdir(dir, subdir);
if (unlikely(d_unhashed(subdir) || d_is_negative(subdir))) {
- dput(subdir);
+ end_creating(subdir, dir);
goto retry;
}
ASSERT(d_backing_inode(subdir));
@@ -154,7 +153,8 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
/* Tell rmdir() it's not allowed to delete the subdir */
inode_lock(d_inode(subdir));
- inode_unlock(d_inode(dir));
+ dget(subdir);
+ end_creating(subdir, dir);
if (!__cachefiles_mark_inode_in_use(NULL, d_inode(subdir))) {
pr_notice("cachefiles: Inode already in use: %pd (B=%lx)\n",
@@ -196,14 +196,11 @@ struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
return ERR_PTR(-EBUSY);
mkdir_error:
- inode_unlock(d_inode(dir));
- if (!IS_ERR(subdir))
- dput(subdir);
+ end_creating(subdir, dir);
pr_err("mkdir %s failed with error %d\n", dirname, ret);
return ERR_PTR(ret);
lookup_error:
- inode_unlock(d_inode(dir));
ret = PTR_ERR(subdir);
pr_err("Lookup %s failed with error %d\n", dirname, ret);
return ERR_PTR(ret);
@@ -679,36 +676,37 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache,
_enter(",%pD", object->file);
- inode_lock_nested(d_inode(fan), I_MUTEX_PARENT);
ret = cachefiles_inject_read_error();
if (ret == 0)
- dentry = lookup_one(&nop_mnt_idmap, &QSTR(object->d_name), fan);
+ dentry = start_creating(&nop_mnt_idmap, fan, &QSTR(object->d_name));
else
dentry = ERR_PTR(ret);
if (IS_ERR(dentry)) {
trace_cachefiles_vfs_error(object, d_inode(fan), PTR_ERR(dentry),
cachefiles_trace_lookup_error);
_debug("lookup fail %ld", PTR_ERR(dentry));
- goto out_unlock;
+ goto out;
}
- if (!d_is_negative(dentry)) {
+ while (!d_is_negative(dentry)) {
ret = cachefiles_unlink(volume->cache, object, fan, dentry,
FSCACHE_OBJECT_IS_STALE);
if (ret < 0)
goto out_dput;
- dput(dentry);
+ end_creating(dentry, fan);
+
ret = cachefiles_inject_read_error();
if (ret == 0)
- dentry = lookup_one(&nop_mnt_idmap, &QSTR(object->d_name), fan);
+ dentry = start_creating(&nop_mnt_idmap, fan,
+ &QSTR(object->d_name));
else
dentry = ERR_PTR(ret);
if (IS_ERR(dentry)) {
trace_cachefiles_vfs_error(object, d_inode(fan), PTR_ERR(dentry),
cachefiles_trace_lookup_error);
_debug("lookup fail %ld", PTR_ERR(dentry));
- goto out_unlock;
+ goto out;
}
}
@@ -730,9 +728,8 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache,
}
out_dput:
- dput(dentry);
-out_unlock:
- inode_unlock(d_inode(fan));
+ end_creating(dentry, fan);
+out:
_leave(" = %u", success);
return success;
}
diff --git a/fs/namei.c b/fs/namei.c
index c1e39c985f1f..407f3516b335 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3161,6 +3161,31 @@ struct dentry *lookup_noperm_positive_unlocked(struct qstr *name,
}
EXPORT_SYMBOL(lookup_noperm_positive_unlocked);
+/**
+ * start_creating - prepare to create a given name with permission checking
+ * @idmap - idmap of the mount
+ * @parent - directory in which to prepare to create the name
+ * @name - the name to be created
+ *
+ * Locks are taken and a lookup in performed prior to creating
+ * an object in a directory. Permission checking (MAY_EXEC) is performed
+ * against @idmap.
+ *
+ * If the name already exists, a positive dentry is returned.
+ *
+ * Returns: a negative or positive dentry, or an error.
+ */
+struct dentry *start_creating(struct mnt_idmap *idmap, struct dentry *parent,
+ struct qstr *name)
+{
+ int err = lookup_one_common(idmap, name, parent);
+
+ if (err)
+ return ERR_PTR(err);
+ return start_dirop(parent, name, LOOKUP_CREATE);
+}
+EXPORT_SYMBOL(start_creating);
+
#ifdef CONFIG_UNIX98_PTYS
int path_pts(struct path *path)
{
diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index b6d03e1ef5f7..e2aac0def2cb 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -281,14 +281,11 @@ nfsd3_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
if (host_err)
return nfserrno(host_err);
- inode_lock_nested(inode, I_MUTEX_PARENT);
-
- child = lookup_one(&nop_mnt_idmap,
- &QSTR_LEN(argp->name, argp->len),
- parent);
+ child = start_creating(&nop_mnt_idmap, parent,
+ &QSTR_LEN(argp->name, argp->len));
if (IS_ERR(child)) {
status = nfserrno(PTR_ERR(child));
- goto out;
+ goto out_write;
}
if (d_really_is_negative(child)) {
@@ -367,9 +364,8 @@ nfsd3_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
status = nfsd_create_setattr(rqstp, fhp, resfhp, &attrs);
out:
- inode_unlock(inode);
- if (child && !IS_ERR(child))
- dput(child);
+ end_creating(child, parent);
+out_write:
fh_drop_write(fhp);
return status;
}
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 71b428efcbb5..35d48221072f 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -264,14 +264,11 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
if (is_create_with_attrs(open))
nfsd4_acl_to_attr(NF4REG, open->op_acl, &attrs);
- inode_lock_nested(inode, I_MUTEX_PARENT);
-
- child = lookup_one(&nop_mnt_idmap,
- &QSTR_LEN(open->op_fname, open->op_fnamelen),
- parent);
+ child = start_creating(&nop_mnt_idmap, parent,
+ &QSTR_LEN(open->op_fname, open->op_fnamelen));
if (IS_ERR(child)) {
status = nfserrno(PTR_ERR(child));
- goto out;
+ goto out_write;
}
if (d_really_is_negative(child)) {
@@ -379,10 +376,9 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
if (attrs.na_aclerr)
open->op_bmval[0] &= ~FATTR4_WORD0_ACL;
out:
- inode_unlock(inode);
+ end_creating(child, parent);
nfsd_attrs_free(&attrs);
- if (child && !IS_ERR(child))
- dput(child);
+out_write:
fh_drop_write(fhp);
return status;
}
diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index 2231192ec33f..93b2a3e764db 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -216,13 +216,11 @@ nfsd4_create_clid_dir(struct nfs4_client *clp)
goto out_creds;
dir = nn->rec_file->f_path.dentry;
- /* lock the parent */
- inode_lock(d_inode(dir));
- dentry = lookup_one(&nop_mnt_idmap, &QSTR(dname), dir);
+ dentry = start_creating(&nop_mnt_idmap, dir, &QSTR(dname));
if (IS_ERR(dentry)) {
status = PTR_ERR(dentry);
- goto out_unlock;
+ goto out;
}
if (d_really_is_positive(dentry))
/*
@@ -233,15 +231,13 @@ nfsd4_create_clid_dir(struct nfs4_client *clp)
* In the 4.0 case, we should never get here; but we may
* as well be forgiving and just succeed silently.
*/
- goto out_put;
+ goto out_end;
dentry = vfs_mkdir(&nop_mnt_idmap, d_inode(dir), dentry, S_IRWXU);
if (IS_ERR(dentry))
status = PTR_ERR(dentry);
-out_put:
- if (!status)
- dput(dentry);
-out_unlock:
- inode_unlock(d_inode(dir));
+out_end:
+ end_creating(dentry, dir);
+out:
if (status == 0) {
if (nn->in_grace)
__nfsd4_create_reclaim_record_grace(clp, dname,
diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
index 8f71f5748c75..ee1b16e921fd 100644
--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -306,18 +306,16 @@ nfsd_proc_create(struct svc_rqst *rqstp)
goto done;
}
- inode_lock_nested(dirfhp->fh_dentry->d_inode, I_MUTEX_PARENT);
- dchild = lookup_one(&nop_mnt_idmap, &QSTR_LEN(argp->name, argp->len),
- dirfhp->fh_dentry);
+ dchild = start_creating(&nop_mnt_idmap, dirfhp->fh_dentry,
+ &QSTR_LEN(argp->name, argp->len));
if (IS_ERR(dchild)) {
resp->status = nfserrno(PTR_ERR(dchild));
- goto out_unlock;
+ goto out_write;
}
fh_init(newfhp, NFS_FHSIZE);
resp->status = fh_compose(newfhp, dirfhp->fh_export, dchild, dirfhp);
if (!resp->status && d_really_is_negative(dchild))
resp->status = nfserr_noent;
- dput(dchild);
if (resp->status) {
if (resp->status != nfserr_noent)
goto out_unlock;
@@ -423,7 +421,8 @@ nfsd_proc_create(struct svc_rqst *rqstp)
}
out_unlock:
- inode_unlock(dirfhp->fh_dentry->d_inode);
+ end_creating(dchild, dirfhp->fh_dentry);
+out_write:
fh_drop_write(dirfhp);
done:
fh_put(dirfhp);
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 5f3e99f956ca..5c809cbc05fe 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1597,19 +1597,16 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
if (host_err)
return nfserrno(host_err);
- inode_lock_nested(dentry->d_inode, I_MUTEX_PARENT);
- dchild = lookup_one(&nop_mnt_idmap, &QSTR_LEN(fname, flen), dentry);
+ dchild = start_creating(&nop_mnt_idmap, dentry, &QSTR_LEN(fname, flen));
host_err = PTR_ERR(dchild);
- if (IS_ERR(dchild)) {
- err = nfserrno(host_err);
- goto out_unlock;
- }
+ if (IS_ERR(dchild))
+ return nfserrno(host_err);
+
err = fh_compose(resfhp, fhp->fh_export, dchild, fhp);
/*
* We unconditionally drop our ref to dchild as fh_compose will have
* already grabbed its own ref for it.
*/
- dput(dchild);
if (err)
goto out_unlock;
err = fh_fill_pre_attrs(fhp);
@@ -1618,7 +1615,7 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
err = nfsd_create_locked(rqstp, fhp, attrs, type, rdev, resfhp);
fh_fill_post_attrs(fhp);
out_unlock:
- inode_unlock(dentry->d_inode);
+ end_creating(dchild, dentry);
return err;
}
@@ -1704,11 +1701,9 @@ nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
}
dentry = fhp->fh_dentry;
- inode_lock_nested(dentry->d_inode, I_MUTEX_PARENT);
- dnew = lookup_one(&nop_mnt_idmap, &QSTR_LEN(fname, flen), dentry);
+ dnew = start_creating(&nop_mnt_idmap, dentry, &QSTR_LEN(fname, flen));
if (IS_ERR(dnew)) {
err = nfserrno(PTR_ERR(dnew));
- inode_unlock(dentry->d_inode);
goto out_drop_write;
}
err = fh_fill_pre_attrs(fhp);
@@ -1721,11 +1716,11 @@ nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
nfsd_create_setattr(rqstp, fhp, resfhp, attrs);
fh_fill_post_attrs(fhp);
out_unlock:
- inode_unlock(dentry->d_inode);
+ end_creating(dnew, dentry);
if (!err)
err = nfserrno(commit_metadata(fhp));
- dput(dnew);
- if (err==0) err = cerr;
+ if (err==0)
+ err = cerr;
out_drop_write:
fh_drop_write(fhp);
out:
@@ -1780,32 +1775,31 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
ddir = ffhp->fh_dentry;
dirp = d_inode(ddir);
- inode_lock_nested(dirp, I_MUTEX_PARENT);
+ dnew = start_creating(&nop_mnt_idmap, ddir, &QSTR_LEN(name, len));
- dnew = lookup_one(&nop_mnt_idmap, &QSTR_LEN(name, len), ddir);
if (IS_ERR(dnew)) {
host_err = PTR_ERR(dnew);
- goto out_unlock;
+ goto out_drop_write;
}
dold = tfhp->fh_dentry;
err = nfserr_noent;
if (d_really_is_negative(dold))
- goto out_dput;
+ goto out_unlock;
err = fh_fill_pre_attrs(ffhp);
if (err != nfs_ok)
- goto out_dput;
+ goto out_unlock;
host_err = vfs_link(dold, &nop_mnt_idmap, dirp, dnew, NULL);
fh_fill_post_attrs(ffhp);
- inode_unlock(dirp);
+out_unlock:
+ end_creating(dnew, ddir);
if (!host_err) {
host_err = commit_metadata(ffhp);
if (!host_err)
host_err = commit_metadata(tfhp);
}
- dput(dnew);
out_drop_write:
fh_drop_write(tfhp);
if (host_err == -EBUSY) {
@@ -1820,12 +1814,6 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
}
out:
return err != nfs_ok ? err : nfserrno(host_err);
-
-out_dput:
- dput(dnew);
-out_unlock:
- inode_unlock(dirp);
- goto out_drop_write;
}
static void
diff --git a/include/linux/namei.h b/include/linux/namei.h
index b1171aa7fb96..7371f586e318 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -81,9 +81,27 @@ struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
struct qstr *name,
struct dentry *base);
+struct dentry *start_creating(struct mnt_idmap *idmap, struct dentry *parent,
+ struct qstr *name);
+
void end_dirop(struct dentry *de);
void end_dirop_mkdir(struct dentry *de, struct dentry *parent);
+/* end_creating - finish action started with start_creating
+ * @child - dentry returned by start_creating()
+ * @parent - dentry given to start_creating()
+ *
+ * Unlock and release the child.
+ *
+ * Unlike end_dirop() this can only be called if start_creating() succeeded.
+ * It handles @child being and error as vfs_mkdir() might have converted the
+ * dentry to an error - in that case the parent still needs to be unlocked.
+ */
+static inline void end_creating(struct dentry *child, struct dentry *parent)
+{
+ end_dirop_mkdir(child, parent);
+}
+
/* filesystems which use the dcache as backing store don't
* keep a reference after creating an object.
*/
--
2.50.0.107.gf914562f5916.dirty
