From dd662667e6d3e55b42798a6e6e7f37dddc639460 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Sat, 13 Dec 2014 00:59:43 +0100 Subject: [PATCH] ovl: add mutli-layer infrastructure Add multiple lower layers to 'struct ovl_fs' and 'struct ovl_entry'. ovl_entry will have an array of paths, instead of just the dentry. This allows a compact array containing just the layers which exist at current point in the tree (which is expected to be a small number for the majority of dentries). The number of layers is not limited by this infrastructure. Signed-off-by: Miklos Szeredi --- fs/overlayfs/super.c | 98 +++++++++++++++++++++++++++++--------------- 1 file changed, 64 insertions(+), 34 deletions(-) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 821719cc8537..460d866b97a2 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -35,7 +35,8 @@ struct ovl_config { /* private information held for overlayfs's superblock */ struct ovl_fs { struct vfsmount *upper_mnt; - struct vfsmount *lower_mnt; + unsigned numlower; + struct vfsmount **lower_mnt; struct dentry *workdir; long lower_namelen; /* pathnames of lower and upper dirs, for show_options */ @@ -47,7 +48,6 @@ struct ovl_dir_cache; /* private information held for every overlayfs dentry */ struct ovl_entry { struct dentry *__upperdentry; - struct dentry *lowerdentry; struct ovl_dir_cache *cache; union { struct { @@ -56,10 +56,16 @@ struct ovl_entry { }; struct rcu_head rcu; }; + unsigned numlower; + struct path lowerstack[]; }; const char *ovl_opaque_xattr = "trusted.overlay.opaque"; +static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe) +{ + return oe->numlower ? oe->lowerstack[0].dentry : NULL; +} enum ovl_path_type ovl_path_type(struct dentry *dentry) { @@ -69,7 +75,7 @@ enum ovl_path_type ovl_path_type(struct dentry *dentry) if (oe->__upperdentry) { type = __OVL_PATH_UPPER; - if (oe->lowerdentry) { + if (oe->numlower) { if (S_ISDIR(dentry->d_inode->i_mode)) type |= __OVL_PATH_MERGE; } else if (!oe->opaque) { @@ -117,7 +123,7 @@ struct dentry *ovl_dentry_lower(struct dentry *dentry) { struct ovl_entry *oe = dentry->d_fsdata; - return oe->lowerdentry; + return __ovl_dentry_lower(oe); } struct dentry *ovl_dentry_real(struct dentry *dentry) @@ -127,7 +133,7 @@ struct dentry *ovl_dentry_real(struct dentry *dentry) realdentry = ovl_upperdentry_dereference(oe); if (!realdentry) - realdentry = oe->lowerdentry; + realdentry = __ovl_dentry_lower(oe); return realdentry; } @@ -140,7 +146,7 @@ struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper) if (realdentry) { *is_upper = true; } else { - realdentry = oe->lowerdentry; + realdentry = __ovl_dentry_lower(oe); *is_upper = false; } return realdentry; @@ -162,11 +168,9 @@ void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache) void ovl_path_lower(struct dentry *dentry, struct path *path) { - struct ovl_fs *ofs = dentry->d_sb->s_fs_info; struct ovl_entry *oe = dentry->d_fsdata; - path->mnt = ofs->lower_mnt; - path->dentry = oe->lowerdentry; + *path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL }; } int ovl_want_write(struct dentry *dentry) @@ -258,8 +262,11 @@ static void ovl_dentry_release(struct dentry *dentry) struct ovl_entry *oe = dentry->d_fsdata; if (oe) { + unsigned int i; + dput(oe->__upperdentry); - dput(oe->lowerdentry); + for (i = 0; i < oe->numlower; i++) + dput(oe->lowerstack[i].dentry); kfree_rcu(oe, rcu); } } @@ -268,9 +275,15 @@ static const struct dentry_operations ovl_dentry_operations = { .d_release = ovl_dentry_release, }; -static struct ovl_entry *ovl_alloc_entry(void) +static struct ovl_entry *ovl_alloc_entry(unsigned int numlower) { - return kzalloc(sizeof(struct ovl_entry), GFP_KERNEL); + size_t size = offsetof(struct ovl_entry, lowerstack[numlower]); + struct ovl_entry *oe = kzalloc(size, GFP_KERNEL); + + if (oe) + oe->numlower = numlower; + + return oe; } static inline struct dentry *ovl_lookup_real(struct dentry *dir, @@ -297,19 +310,19 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, { struct ovl_entry *oe; struct dentry *upperdir; - struct dentry *lowerdir; + struct path lowerdir; struct dentry *upperdentry = NULL; struct dentry *lowerdentry = NULL; struct inode *inode = NULL; int err; err = -ENOMEM; - oe = ovl_alloc_entry(); + oe = ovl_alloc_entry(1); if (!oe) goto out; upperdir = ovl_dentry_upper(dentry->d_parent); - lowerdir = ovl_dentry_lower(dentry->d_parent); + ovl_path_lower(dentry->d_parent, &lowerdir); if (upperdir) { upperdentry = ovl_lookup_real(upperdir, &dentry->d_name); @@ -317,7 +330,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, if (IS_ERR(upperdentry)) goto out_put_dir; - if (lowerdir && upperdentry) { + if (lowerdir.dentry && upperdentry) { if (ovl_is_whiteout(upperdentry)) { dput(upperdentry); upperdentry = NULL; @@ -327,8 +340,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, } } } - if (lowerdir && !oe->opaque) { - lowerdentry = ovl_lookup_real(lowerdir, &dentry->d_name); + if (lowerdir.dentry && !oe->opaque) { + lowerdentry = ovl_lookup_real(lowerdir.dentry, &dentry->d_name); err = PTR_ERR(lowerdentry); if (IS_ERR(lowerdentry)) goto out_dput_upper; @@ -355,8 +368,12 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, } oe->__upperdentry = upperdentry; - oe->lowerdentry = lowerdentry; - + if (lowerdentry) { + oe->lowerstack[0].dentry = lowerdentry; + oe->lowerstack[0].mnt = lowerdir.mnt; + } else { + oe->numlower = 0; + } dentry->d_fsdata = oe; d_add(dentry, inode); @@ -380,10 +397,12 @@ struct file *ovl_path_open(struct path *path, int flags) static void ovl_put_super(struct super_block *sb) { struct ovl_fs *ufs = sb->s_fs_info; + unsigned i; dput(ufs->workdir); mntput(ufs->upper_mnt); - mntput(ufs->lower_mnt); + for (i = 0; i < ufs->numlower; i++) + mntput(ufs->lower_mnt[i]); kfree(ufs->config.lowerdir); kfree(ufs->config.upperdir); @@ -641,6 +660,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) struct ovl_entry *oe; struct ovl_fs *ufs; struct kstatfs statfs; + struct vfsmount *mnt; + unsigned int i; int err; err = -ENOMEM; @@ -661,7 +682,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) } err = -ENOMEM; - oe = ovl_alloc_entry(); + oe = ovl_alloc_entry(1); if (oe == NULL) goto out_free_config; @@ -727,12 +748,24 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) goto out_put_workpath; } - ufs->lower_mnt = clone_private_mount(&lowerpath); - err = PTR_ERR(ufs->lower_mnt); - if (IS_ERR(ufs->lower_mnt)) { - pr_err("overlayfs: failed to clone lowerpath\n"); + ufs->lower_mnt = kcalloc(1, sizeof(struct vfsmount *), GFP_KERNEL); + if (ufs->lower_mnt == NULL) goto out_put_upper_mnt; + + mnt = clone_private_mount(&lowerpath); + err = PTR_ERR(mnt); + if (IS_ERR(mnt)) { + pr_err("overlayfs: failed to clone lowerpath\n"); + goto out_put_lower_mnt; } + /* + * Make lower_mnt R/O. That way fchmod/fchown on lower file + * will fail instead of modifying lower fs. + */ + mnt->mnt_flags |= MNT_READONLY; + + ufs->lower_mnt[0] = mnt; + ufs->numlower = 1; ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry); err = PTR_ERR(ufs->workdir); @@ -742,12 +775,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) goto out_put_lower_mnt; } - /* - * Make lower_mnt R/O. That way fchmod/fchown on lower file - * will fail instead of modifying lower fs. - */ - ufs->lower_mnt->mnt_flags |= MNT_READONLY; - /* If the upper fs is r/o, we mark overlayfs r/o too */ if (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY) sb->s_flags |= MS_RDONLY; @@ -768,7 +795,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) path_put(&workpath); oe->__upperdentry = upperpath.dentry; - oe->lowerdentry = lowerpath.dentry; + oe->lowerstack[0].dentry = lowerpath.dentry; + oe->lowerstack[0].mnt = ufs->lower_mnt[0]; root_dentry->d_fsdata = oe; @@ -782,7 +810,9 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) out_put_workdir: dput(ufs->workdir); out_put_lower_mnt: - mntput(ufs->lower_mnt); + for (i = 0; i < ufs->numlower; i++) + mntput(ufs->lower_mnt[i]); + kfree(ufs->lower_mnt); out_put_upper_mnt: mntput(ufs->upper_mnt); out_put_workpath: -- 2.20.1