Commit 8a22efa1 authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
Browse files

ovl: do not try to reconnect a disconnected origin dentry 



On lookup of non directory, we try to decode the origin file handle
stored in upper inode. The origin file handle is supposed to be decoded
to a disconnected non-dir dentry, which is fine, because we only need
the lower inode of a copy up origin.

However, if the origin file handle somehow turns out to be a directory
we pay the expensive cost of reconnecting the directory dentry, only to
get a mismatch file type and drop the dentry.

Optimize this case by explicitly opting out of reconnecting the dentry.
Opting-out of reconnect is done by passing a NULL acceptable callback
to exportfs_decode_fh().

While the case described above is a strange corner case that does not
really need to be optimized, the API added for this optimization will
be used by a following patch to optimize a more common case of decoding
an overlayfs file handle.

Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 5b2cccd3

fs/exportfs/expfs.c

+9 −0
Original line number Diff line number Diff line
@@ -435,6 +435,15 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid, 
	if (IS_ERR_OR_NULL(result))

		return ERR_PTR(-ESTALE);



	/*

	 * If no acceptance criteria was specified by caller, a disconnected

	 * dentry is also accepatable. Callers may use this mode to query if

	 * file handle is stale or to get a reference to an inode without

	 * risking the high overhead caused by directory reconnect.

	 */

	if (!acceptable)

		return result;



	if (d_is_dir(result)) {

		/*

		 * This request is for a directory.

fs/overlayfs/export.c

+2 −2
Original line number Diff line number Diff line
@@ -685,7 +685,7 @@ static struct dentry *ovl_upper_fh_to_d(struct super_block *sb, 
	if (!ofs->upper_mnt)

		return ERR_PTR(-EACCES);



	upper = ovl_decode_real_fh(fh, ofs->upper_mnt);

	upper = ovl_decode_real_fh(fh, ofs->upper_mnt, true);

	if (IS_ERR_OR_NULL(upper))

		return upper;
@@ -735,7 +735,7 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb, 
	}



	/* Then lookup origin by fh */

	err = ovl_check_origin_fh(ofs, fh, NULL, &stack);

	err = ovl_check_origin_fh(ofs, fh, true, NULL, &stack);

	if (err) {

		goto out_err;

	} else if (index) {

fs/overlayfs/namei.c

+9 −7
Original line number Diff line number Diff line
@@ -180,7 +180,8 @@ invalid: 
	goto out;

}



struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt)

struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt,

				  bool connected)

{

	struct dentry *real;

	int bytes;
@@ -195,7 +196,7 @@ struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt) 
	bytes = (fh->len - offsetof(struct ovl_fh, fid));

	real = exportfs_decode_fh(mnt, (struct fid *)fh->fid,

				  bytes >> 2, (int)fh->type,

				  ovl_acceptable, mnt);

				  connected ? ovl_acceptable : NULL, mnt);

	if (IS_ERR(real)) {

		/*

		 * Treat stale file handle to lower file as "origin unknown".
@@ -319,14 +320,15 @@ static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d, 
}





int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh,

int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,

			struct dentry *upperdentry, struct ovl_path **stackp)

{

	struct dentry *origin = NULL;

	int i;



	for (i = 0; i < ofs->numlower; i++) {

		origin = ovl_decode_real_fh(fh, ofs->lower_layers[i].mnt);

		origin = ovl_decode_real_fh(fh, ofs->lower_layers[i].mnt,

					    connected);

		if (origin)

			break;

	}
@@ -370,7 +372,7 @@ static int ovl_check_origin(struct ovl_fs *ofs, struct dentry *upperdentry, 
	if (IS_ERR_OR_NULL(fh))

		return PTR_ERR(fh);



	err = ovl_check_origin_fh(ofs, fh, upperdentry, stackp);

	err = ovl_check_origin_fh(ofs, fh, false, upperdentry, stackp);

	kfree(fh);



	if (err) {
@@ -460,7 +462,7 @@ struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index) 
	if (IS_ERR_OR_NULL(fh))

		return ERR_CAST(fh);



	upper = ovl_decode_real_fh(fh, ofs->upper_mnt);

	upper = ovl_decode_real_fh(fh, ofs->upper_mnt, true);

	kfree(fh);



	if (IS_ERR_OR_NULL(upper))
@@ -567,7 +569,7 @@ int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index) 


	/* Check if non-dir index is orphan and don't warn before cleaning it */

	if (!d_is_dir(index) && d_inode(index)->i_nlink == 1) {

		err = ovl_check_origin_fh(ofs, fh, index, &stack);

		err = ovl_check_origin_fh(ofs, fh, false, index, &stack);

		if (err)

			goto fail;

fs/overlayfs/overlayfs.h

+3 −2
Original line number Diff line number Diff line
@@ -266,8 +266,9 @@ static inline bool ovl_is_impuredir(struct dentry *dentry) 


/* namei.c */

int ovl_check_fh_len(struct ovl_fh *fh, int fh_len);

struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt);

int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh,

struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt,

				  bool connected);

int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,

			struct dentry *upperdentry, struct ovl_path **stackp);

int ovl_verify_set_fh(struct dentry *dentry, const char *name,

		      struct dentry *real, bool is_upper, bool set);

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