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ceph: don't use d_add in ceph_handle_snapdir 

It's possible ceph_get_snapdir could end up finding a (disconnected)
inode that already exists in the cache. Change the prototype for
ceph_handle_snapdir to return a dentry pointer and have it use
d_splice_alias so we don't end up with an aliased dentry in the cache.

Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Jeff Layton 2021-03-01 08:01:54 -05:00 committed by Ilya Dryomov
parent d3c51ae1b8
commit aa60cfc3f7
3 changed files with 25 additions and 14 deletions
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30
fs/ceph/dir.c
View File

@ -667,8 +667,8 @@ out:
/*
* Handle lookups for the hidden .snap directory.
*/
int ceph_handle_snapdir(struct ceph_mds_request *req,
struct dentry *dentry, int err)
struct dentry *ceph_handle_snapdir(struct ceph_mds_request *req,
struct dentry *dentry, int err)
{
struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);
struct inode *parent = d_inode(dentry->d_parent); /* we hold i_mutex */
@ -676,16 +676,17 @@ int ceph_handle_snapdir(struct ceph_mds_request *req,
/* .snap dir? */
if (err == -ENOENT &&
ceph_snap(parent) == CEPH_NOSNAP &&
strcmp(dentry->d_name.name,
fsc->mount_options->snapdir_name) == 0) {
strcmp(dentry->d_name.name, fsc->mount_options->snapdir_name) == 0) {
struct dentry *res;
struct inode *inode = ceph_get_snapdir(parent);
dout("ENOENT on snapdir %p '%pd', linking to snapdir %p\n",
dentry, dentry, inode);
BUG_ON(!d_unhashed(dentry));
d_add(dentry, inode);
err = 0;
res = d_splice_alias(inode, dentry);
dout("ENOENT on snapdir %p '%pd', linking to snapdir %p. Spliced dentry %p\n",
dentry, dentry, inode, res);
if (res)
dentry = res;
}
return err;
return dentry;
}
/*
@ -741,6 +742,7 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
struct ceph_fs_client *fsc = ceph_sb_to_client(dir->i_sb);
struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(dir->i_sb);
struct ceph_mds_request *req;
struct dentry *res;
int op;
int mask;
int err;
@ -791,7 +793,13 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
req->r_parent = dir;
set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
err = ceph_mdsc_do_request(mdsc, NULL, req);
err = ceph_handle_snapdir(req, dentry, err);
res = ceph_handle_snapdir(req, dentry, err);
if (IS_ERR(res)) {
err = PTR_ERR(res);
} else {
dentry = res;
err = 0;
}
dentry = ceph_finish_lookup(req, dentry, err);
ceph_mdsc_put_request(req); /* will dput(dentry) */
dout("lookup result=%p\n", dentry);

7
fs/ceph/file.c
View File

@ -739,9 +739,12 @@ retry:
err = ceph_mdsc_do_request(mdsc,
(flags & (O_CREAT|O_TRUNC)) ? dir : NULL,
req);
err = ceph_handle_snapdir(req, dentry, err);
if (err)
dentry = ceph_handle_snapdir(req, dentry, err);
if (IS_ERR(dentry)) {
err = PTR_ERR(dentry);
goto out_req;
}
err = 0;
if ((flags & O_CREAT) && !req->r_reply_info.head->is_dentry)
err = ceph_handle_notrace_create(dir, dentry);

2
fs/ceph/super.h
View File

@ -1193,7 +1193,7 @@ extern const struct dentry_operations ceph_dentry_ops;
extern loff_t ceph_make_fpos(unsigned high, unsigned off, bool hash_order);
extern int ceph_handle_notrace_create(struct inode *dir, struct dentry *dentry);
extern int ceph_handle_snapdir(struct ceph_mds_request *req,
extern struct dentry *ceph_handle_snapdir(struct ceph_mds_request *req,
struct dentry *dentry, int err);
extern struct dentry *ceph_finish_lookup(struct ceph_mds_request *req,
struct dentry *dentry, int err);