Re: [PATCH v4 2/2] ceph: do not dencrypt the dentry name twice for readdir

[Xiubo Li <xiubli@xxxxxxxxxx>]

On 3/5/22 1:57 AM, Jeff Layton wrote:
> On Thu, 2022-03-03 at 11:26 +0800, xiubli@xxxxxxxxxx wrote:
> > From: Xiubo Li <xiubli@xxxxxxxxxx>
> >
> > For the readdir request the dentries will be pasred and dencrypted
> > in ceph_readdir_prepopulate(). And in ceph_readdir() we could just
> > get the dentry name from the dentry cache instead of parsing and
> > dencrypting them again. This could improve performance.
> >
> > Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
> > ---
> >   fs/ceph/crypto.h     |  8 +++++
> >   fs/ceph/dir.c        | 74 +++++++++++++++++++++++---------------------
> >   fs/ceph/inode.c      | 15 +++++++++
> >   fs/ceph/mds_client.h |  1 +
> >   4 files changed, 63 insertions(+), 35 deletions(-)
> >
> > diff --git a/fs/ceph/crypto.h b/fs/ceph/crypto.h
> > index 1e08f8a64ad6..9a00c60b8535 100644
> > --- a/fs/ceph/crypto.h
> > +++ b/fs/ceph/crypto.h
> > @@ -83,6 +83,14 @@ static inline u32 ceph_fscrypt_auth_len(struct ceph_fscrypt_auth *fa)
> >    */
> >   #define CEPH_NOHASH_NAME_MAX (189 - SHA256_DIGEST_SIZE)
> >   
> > +/*
> > + * The encrypted long snap name will be in format of
> > + * "_${ENCRYPTED-LONG-SNAP-NAME}_${INODE-NUM}". And will set the max longth
> > + * to sizeof('_') + NAME_MAX + sizeof('_') + max of sizeof(${INO}) + extra 7
> > + * bytes to align the total size to 8 bytes.
> > + */
> > +#define CEPH_ENCRPTED_LONG_SNAP_NAME_MAX (1 + 255 + 1 + 16 + 7)
> > +
> Maybe CEPH_ENCRYPTED_LONG_SNAP_NAME_MAX instead?

Sure, will fix it.


> >   void ceph_fscrypt_set_ops(struct super_block *sb);
> >   
> >   void ceph_fscrypt_free_dummy_policy(struct ceph_fs_client *fsc);
> > diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
> > index 4da59810b036..fa3da3b29130 100644
> > --- a/fs/ceph/dir.c
> > +++ b/fs/ceph/dir.c
> > @@ -316,8 +316,7 @@ static int ceph_readdir(struct file *file, struct dir_context *ctx)
> >   	int err;
> >   	unsigned frag = -1;
> >   	struct ceph_mds_reply_info_parsed *rinfo;
> > -	struct fscrypt_str tname = FSTR_INIT(NULL, 0);
> > -	struct fscrypt_str oname = FSTR_INIT(NULL, 0);
> > +	char *dentry_name = NULL;
> >   
> >   	dout("readdir %p file %p pos %llx\n", inode, file, ctx->pos);
> >   	if (dfi->file_info.flags & CEPH_F_ATEND)
> > @@ -345,10 +344,6 @@ static int ceph_readdir(struct file *file, struct dir_context *ctx)
> >   		ctx->pos = 2;
> >   	}
> >   
> > -	err = fscrypt_prepare_readdir(inode);
> > -	if (err)
> > -		goto out;
> > -
> >   	spin_lock(&ci->i_ceph_lock);
> >   	/* request Fx cap. if have Fx, we don't need to release Fs cap
> >   	 * for later create/unlink. */
> > @@ -369,14 +364,6 @@ static int ceph_readdir(struct file *file, struct dir_context *ctx)
> >   		spin_unlock(&ci->i_ceph_lock);
> >   	}
> >   
> > -	err = ceph_fname_alloc_buffer(inode, &tname);
> > -	if (err < 0)
> > -		goto out;
> > -
> > -	err = ceph_fname_alloc_buffer(inode, &oname);
> > -	if (err < 0)
> > -		goto out;
> > -
> >   	/* proceed with a normal readdir */
> >   more:
> >   	/* do we have the correct frag content buffered? */
> > @@ -528,42 +515,59 @@ static int ceph_readdir(struct file *file, struct dir_context *ctx)
> >   			}
> >   		}
> >   	}
> > +
> > +	dentry_name = kmalloc(CEPH_ENCRPTED_LONG_SNAP_NAME_MAX, GFP_KERNEL);
> > +	if (!dentry_name) {
> > +		err = -ENOMEM;
> > +		ceph_mdsc_put_request(dfi->last_readdir);
> > +		dfi->last_readdir = NULL;
> > +		goto out;
> > +	}
> > +
> If this happens (or an earlier error), all of the dentry references will
> leak. I think you probably need to move the cleanup into
> destroy_reply_info().

Yeah, I will fix it too.

Thanks.


> >   	for (; i < rinfo->dir_nr; i++) {
> >   		struct ceph_mds_reply_dir_entry *rde = rinfo->dir_entries + i;
> > -		struct ceph_fname fname = { .dir	= inode,
> > -					    .name	= rde->name,
> > -					    .name_len	= rde->name_len,
> > -					    .ctext	= rde->altname,
> > -					    .ctext_len	= rde->altname_len };
> > -		u32 olen = oname.len;
> > -
> > -		err = ceph_fname_to_usr(&fname, &tname, &oname, NULL);
> > -		if (err) {
> > -			pr_err("%s unable to decode %.*s, got %d\n", __func__,
> > -			       rde->name_len, rde->name, err);
> > -			goto out;
> > -		}
> > +		struct dentry *dn = rde->dentry;
> > +		int name_len;
> >   
> >   		BUG_ON(rde->offset < ctx->pos);
> >   		BUG_ON(!rde->inode.in);
> > +		BUG_ON(!rde->dentry);
> >   
> >   		ctx->pos = rde->offset;
> > -		dout("readdir (%d/%d) -> %llx '%.*s' %p\n",
> > -		     i, rinfo->dir_nr, ctx->pos,
> > -		     rde->name_len, rde->name, &rde->inode.in);
> >   
> > -		if (!dir_emit(ctx, oname.name, oname.len,
> > +		spin_lock(&dn->d_lock);
> > +		memcpy(dentry_name, dn->d_name.name, dn->d_name.len);
> > +		name_len = dn->d_name.len;
> > +		spin_unlock(&dn->d_lock);
> > +
> > +		dentry_name[name_len] = '\0';
> > +		dout("readdir (%d/%d) -> %llx '%s' %p\n",
> > +		     i, rinfo->dir_nr, ctx->pos, dentry_name, &rde->inode.in);
> > +
> > +		dput(dn);
> > +		rde->dentry = NULL;
> > +
> > +		if (!dir_emit(ctx, dentry_name, name_len,
> >   			      ceph_present_ino(inode->i_sb, le64_to_cpu(rde->inode.in->ino)),
> >   			      le32_to_cpu(rde->inode.in->mode) >> 12)) {
> >   			dout("filldir stopping us...\n");
> > +
> > +			/*
> > +			 * dput the rest dentries. Must do this before
> > +			 * releasing the request.
> > +			 */
> > +			for (++i; i < rinfo->dir_nr; i++) {
> > +				rde = rinfo->dir_entries + i;
> > +				dput(rde->dentry);
> > +				rde->dentry = NULL;
> > +			}
> > +
> >   			err = 0;
> >   			ceph_mdsc_put_request(dfi->last_readdir);
> >   			dfi->last_readdir = NULL;
> >   			goto out;
> >   		}
> >   
> > -		/* Reset the lengths to their original allocated vals */
> > -		oname.len = olen;
> >   		ctx->pos++;
> >   	}
> >   
> > @@ -621,8 +625,8 @@ static int ceph_readdir(struct file *file, struct dir_context *ctx)
> >   	err = 0;
> >   	dout("readdir %p file %p done.\n", inode, file);
> >   out:
> > -	ceph_fname_free_buffer(inode, &tname);
> > -	ceph_fname_free_buffer(inode, &oname);
> > +	if (dentry_name)
> > +		kfree(dentry_name);
> >   	return err;
> >   }
> >   
> > diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> > index e5a9838981ba..d0719feed792 100644
> > --- a/fs/ceph/inode.c
> > +++ b/fs/ceph/inode.c
> > @@ -1902,6 +1902,7 @@ int ceph_readdir_prepopulate(struct ceph_mds_request *req,
> >   			goto out;
> >   		}
> >   
> > +		rde->dentry = NULL;
> >   		dname.name = oname.name;
> >   		dname.len = oname.len;
> >   		dname.hash = full_name_hash(parent, dname.name, dname.len);
> > @@ -1962,6 +1963,12 @@ int ceph_readdir_prepopulate(struct ceph_mds_request *req,
> >   			goto retry_lookup;
> >   		}
> >   
> > +		/*
> > +		 * ceph_readdir will use the dentry to get the name
> > +		 * to avoid doing the dencrypt again there.
> > +		 */
> > +		rde->dentry = dget(dn);
> > +
> >   		/* inode */
> >   		if (d_really_is_positive(dn)) {
> >   			in = d_inode(dn);
> > @@ -2024,6 +2031,14 @@ int ceph_readdir_prepopulate(struct ceph_mds_request *req,
> >   		dput(dn);
> >   	}
> >   out:
> > +	if (err) {
> > +		for (; i >= 0; i--) {
> > +			struct ceph_mds_reply_dir_entry *rde;
> > +
> > +			rde = rinfo->dir_entries + i;
> > +			dput(rde->dentry);
> > +		}
> > +	}
> >   	if (err == 0 && skipped == 0) {
> >   		set_bit(CEPH_MDS_R_DID_PREPOPULATE, &req->r_req_flags);
> >   		req->r_readdir_cache_idx = cache_ctl.index;
> > diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
> > index 0dfe24f94567..663d7754d57d 100644
> > --- a/fs/ceph/mds_client.h
> > +++ b/fs/ceph/mds_client.h
> > @@ -96,6 +96,7 @@ struct ceph_mds_reply_info_in {
> >   };
> >   
> >   struct ceph_mds_reply_dir_entry {
> > +	struct dentry		      *dentry;
> >   	char                          *name;
> >   	u8			      *altname;
> >   	u32                           name_len;