From 8a22efa15b46d524577cac79da63cebca8e8307f Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Fri, 9 Mar 2018 15:51:02 +0200 Subject: [PATCH] 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: Amir Goldstein Signed-off-by: Miklos Szeredi --- fs/exportfs/expfs.c | 9 +++++++++ fs/overlayfs/export.c | 4 ++-- fs/overlayfs/namei.c | 16 +++++++++------- fs/overlayfs/overlayfs.h | 5 +++-- 4 files changed, 23 insertions(+), 11 deletions(-) diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c index 329a5d103846..645158dc33f1 100644 --- a/fs/exportfs/expfs.c +++ b/fs/exportfs/expfs.c @@ -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. diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c index e688cf019460..15411350a7a1 100644 --- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -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) { diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c index 24bd387321d1..810a333d2221 100644 --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -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; diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index dd6c10e5a7db..b51613b355c5 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -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); -- 2.30.2