aufs: dirren 3/6, save the detailed info per a dir

The detailed info per renamed directory is stored in a regular file per
branch, ie. when each of two lower branches contains the same named
entry, then the created info files will be two.
The file is created internally by aufs rename(2) and loaded by lookup.
Also when the actual rename on the branch fails, the newly created or
stored info file should be all reverted.

When the renamed dir is renamed-back to the previous/original name, then
the info file has to be removed.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/dirren.c

@@ -391,7 +391,6 @@ int au_dr_br_fin(struct super_block *sb, struct au_branch *br)
 
 /* ---------------------------------------------------------------------- */
 
-/* re-commit later */ __maybe_unused
 static int au_brid_str(struct au_dr_brid *brid, struct inode *h_inode,
 		       char *buf, size_t sz)
 {
@@ -433,3 +432,440 @@ static int au_brid_str(struct au_dr_brid *brid, struct inode *h_inode,
 
 	return p - buf;
 }
+
+static int au_drinfo_name(struct au_branch *br, char *name, int len)
+{
+	int rlen;
+	struct dentry *br_dentry;
+	struct inode *br_inode;
+
+	br_dentry = au_br_dentry(br);
+	br_inode = d_inode(br_dentry);
+	rlen = au_brid_str(&br->br_dirren.dr_brid, br_inode, name, len);
+	AuDebugOn(rlen >= AUFS_DIRREN_ENV_VAL_SZ);
+	AuDebugOn(rlen > len);
+
+	return rlen;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/*
+ * from the given @h_dentry, construct drinfo at @*fdata.
+ * when the size of @*fdata is not enough, reallocate and return new @fdata and
+ * @allocated.
+ */
+static int au_drinfo_construct(struct au_drinfo_fdata **fdata,
+			       struct dentry *h_dentry,
+			       unsigned char *allocated)
+{
+	int err, v;
+	struct au_drinfo_fdata *f, *p;
+	struct au_drinfo *drinfo;
+	struct inode *h_inode;
+	struct qstr *qname;
+
+	err = 0;
+	f = *fdata;
+	h_inode = d_inode(h_dentry);
+	qname = &h_dentry->d_name;
+	drinfo = &f->drinfo;
+	drinfo->ino = (__force uint64_t)cpu_to_be64(h_inode->i_ino);
+	drinfo->oldnamelen = qname->len;
+	if (*allocated < sizeof(*f) + qname->len) {
+		v = roundup_pow_of_two(*allocated + qname->len);
+		p = au_krealloc(f, v, GFP_NOFS, /*may_shrink*/0);
+		if (unlikely(!p)) {
+			err = -ENOMEM;
+			AuTraceErr(err);
+			goto out;
+		}
+		f = p;
+		*fdata = f;
+		*allocated = v;
+		drinfo = &f->drinfo;
+	}
+	memcpy(drinfo->oldname, qname->name, qname->len);
+	AuDbg("i%llu, %.*s\n",
+	      be64_to_cpu((__force __be64)drinfo->ino), drinfo->oldnamelen,
+	      drinfo->oldname);
+
+out:
+	AuTraceErr(err);
+	return err;
+}
+
+/* callers have to free the return value */
+static struct au_drinfo *au_drinfo_read_k(struct file *file, ino_t h_ino)
+{
+	struct au_drinfo *ret, *drinfo;
+	struct au_drinfo_fdata fdata;
+	int len;
+	loff_t pos;
+	ssize_t ssz;
+
+	ret = ERR_PTR(-EIO);
+	pos = 0;
+	ssz = vfsub_read_k(file, &fdata, sizeof(fdata), &pos);
+	if (unlikely(ssz != sizeof(fdata))) {
+		AuIOErr("ssz %zd, %u, %pD2\n",
+			ssz, (unsigned int)sizeof(fdata), file);
+		goto out;
+	}
+
+	fdata.magic = ntohl((__force __be32)fdata.magic);
+	switch (fdata.magic) {
+	case AUFS_DRINFO_MAGIC_V1:
+		break;
+	default:
+		AuIOErr("magic-num 0x%x, 0x%x, %pD2\n",
+			fdata.magic, AUFS_DRINFO_MAGIC_V1, file);
+		goto out;
+	}
+
+	drinfo = &fdata.drinfo;
+	len = drinfo->oldnamelen;
+	if (!len) {
+		AuIOErr("broken drinfo %pD2\n", file);
+		goto out;
+	}
+
+	ret = NULL;
+	drinfo->ino = be64_to_cpu((__force __be64)drinfo->ino);
+	if (unlikely(h_ino && drinfo->ino != h_ino)) {
+		AuDbg("ignored i%llu, i%llu, %pD2\n",
+		      (unsigned long long)drinfo->ino,
+		      (unsigned long long)h_ino, file);
+		goto out; /* success */
+	}
+
+	ret = kmalloc(sizeof(*ret) + len, GFP_NOFS);
+	if (unlikely(!ret)) {
+		ret = ERR_PTR(-ENOMEM);
+		AuTraceErrPtr(ret);
+		goto out;
+	}
+
+	*ret = *drinfo;
+	ssz = vfsub_read_k(file, (void *)ret->oldname, len, &pos);
+	if (unlikely(ssz != len)) {
+		au_kfree_rcu(ret);
+		ret = ERR_PTR(-EIO);
+		AuIOErr("ssz %zd, %u, %pD2\n", ssz, len, file);
+		goto out;
+	}
+
+	AuDbg("oldname %.*s\n", ret->oldnamelen, ret->oldname);
+
+out:
+	return ret;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/* in order to be revertible */
+struct au_drinfo_rev_elm {
+	int			created;
+	struct dentry		*info_dentry;
+	struct au_drinfo	*info_last;
+};
+
+struct au_drinfo_rev {
+	unsigned char			already;
+	aufs_bindex_t			nelm;
+	struct au_drinfo_rev_elm	elm[0];
+};
+
+/* todo: isn't it too large? */
+struct au_drinfo_store {
+	struct path h_ppath;
+	struct dentry *h_dentry;
+	struct au_drinfo_fdata *fdata;
+	char *infoname;			/* inside of whname, just after PFX */
+	char whname[sizeof(AUFS_WH_DR_INFO_PFX) + AUFS_DIRREN_ENV_VAL_SZ];
+	aufs_bindex_t btgt, btail;
+	unsigned char no_sio,
+		allocated,		/* current size of *fdata */
+		infonamelen,		/* room size for p */
+		whnamelen,		/* length of the generated name */
+		renameback;		/* renamed back */
+};
+
+/* on rename(2) error, the caller should revert it using @elm */
+static int au_drinfo_do_store(struct au_drinfo_store *w,
+			      struct au_drinfo_rev_elm *elm)
+{
+	int err, len;
+	ssize_t ssz;
+	loff_t pos;
+	struct path infopath = {
+		.mnt = w->h_ppath.mnt
+	};
+	struct inode *h_dir, *h_inode, *delegated;
+	struct file *infofile;
+	struct qstr *qname;
+
+	AuDebugOn(elm
+		  && memcmp(elm, page_address(ZERO_PAGE(0)), sizeof(*elm)));
+
+	infopath.dentry = vfsub_lookup_one_len(w->whname, w->h_ppath.dentry,
+					       w->whnamelen);
+	AuTraceErrPtr(infopath.dentry);
+	if (IS_ERR(infopath.dentry)) {
+		err = PTR_ERR(infopath.dentry);
+		goto out;
+	}
+
+	err = 0;
+	h_dir = d_inode(w->h_ppath.dentry);
+	if (elm && d_is_negative(infopath.dentry)) {
+		err = vfsub_create(h_dir, &infopath, 0600, /*want_excl*/true);
+		AuTraceErr(err);
+		if (unlikely(err))
+			goto out_dput;
+		elm->created = 1;
+		elm->info_dentry = dget(infopath.dentry);
+	}
+
+	infofile = vfsub_dentry_open(&infopath, O_RDWR);
+	AuTraceErrPtr(infofile);
+	if (IS_ERR(infofile)) {
+		err = PTR_ERR(infofile);
+		goto out_dput;
+	}
+
+	h_inode = d_inode(infopath.dentry);
+	if (elm && i_size_read(h_inode)) {
+		h_inode = d_inode(w->h_dentry);
+		elm->info_last = au_drinfo_read_k(infofile, h_inode->i_ino);
+		AuTraceErrPtr(elm->info_last);
+		if (IS_ERR(elm->info_last)) {
+			err = PTR_ERR(elm->info_last);
+			elm->info_last = NULL;
+			AuDebugOn(elm->info_dentry);
+			goto out_fput;
+		}
+	}
+
+	if (elm && w->renameback) {
+		delegated = NULL;
+		err = vfsub_unlink(h_dir, &infopath, &delegated, /*force*/0);
+		AuTraceErr(err);
+		if (unlikely(err == -EWOULDBLOCK))
+			iput(delegated);
+		goto out_fput;
+	}
+
+	pos = 0;
+	qname = &w->h_dentry->d_name;
+	len = sizeof(*w->fdata) + qname->len;
+	if (!elm)
+		len = sizeof(*w->fdata) + w->fdata->drinfo.oldnamelen;
+	ssz = vfsub_write_k(infofile, w->fdata, len, &pos);
+	if (ssz == len) {
+		AuDbg("hi%llu, %.*s\n", w->fdata->drinfo.ino,
+		      w->fdata->drinfo.oldnamelen, w->fdata->drinfo.oldname);
+		goto out_fput; /* success */
+	} else {
+		err = -EIO;
+		if (ssz < 0)
+			err = ssz;
+		/* the caller should revert it using @elm */
+	}
+
+out_fput:
+	fput(infofile);
+out_dput:
+	dput(infopath.dentry);
+out:
+	AuTraceErr(err);
+	return err;
+}
+
+struct au_call_drinfo_do_store_args {
+	int *errp;
+	struct au_drinfo_store *w;
+	struct au_drinfo_rev_elm *elm;
+};
+
+static void au_call_drinfo_do_store(void *args)
+{
+	struct au_call_drinfo_do_store_args *a = args;
+
+	*a->errp = au_drinfo_do_store(a->w, a->elm);
+}
+
+static int au_drinfo_store_sio(struct au_drinfo_store *w,
+			       struct au_drinfo_rev_elm *elm)
+{
+	int err, wkq_err;
+
+	if (w->no_sio)
+		err = au_drinfo_do_store(w, elm);
+	else {
+		struct au_call_drinfo_do_store_args a = {
+			.errp	= &err,
+			.w	= w,
+			.elm	= elm
+		};
+		wkq_err = au_wkq_wait(au_call_drinfo_do_store, &a);
+		if (unlikely(wkq_err))
+			err = wkq_err;
+	}
+	AuTraceErr(err);
+
+	return err;
+}
+
+static int au_drinfo_store_work_init(struct au_drinfo_store *w,
+				     aufs_bindex_t btgt)
+{
+	int err;
+
+	memset(w, 0, sizeof(*w));
+	w->allocated = roundup_pow_of_two(sizeof(*w->fdata) + 40);
+	strcpy(w->whname, AUFS_WH_DR_INFO_PFX);
+	w->infoname = w->whname + sizeof(AUFS_WH_DR_INFO_PFX) - 1;
+	w->infonamelen = sizeof(w->whname) - sizeof(AUFS_WH_DR_INFO_PFX);
+	w->btgt = btgt;
+	w->no_sio = !!uid_eq(current_fsuid(), GLOBAL_ROOT_UID);
+
+	err = -ENOMEM;
+	w->fdata = kcalloc(1, w->allocated, GFP_NOFS);
+	if (unlikely(!w->fdata)) {
+		AuTraceErr(err);
+		goto out;
+	}
+	w->fdata->magic = (__force uint32_t)htonl(AUFS_DRINFO_MAGIC_V1);
+	err = 0;
+
+out:
+	return err;
+}
+
+static void au_drinfo_store_work_fin(struct au_drinfo_store *w)
+{
+	au_kfree_rcu(w->fdata);
+}
+
+static void au_drinfo_store_rev(struct au_drinfo_rev *rev,
+				struct au_drinfo_store *w)
+{
+	struct au_drinfo_rev_elm *elm;
+	struct inode *h_dir, *delegated;
+	int err, nelm;
+	struct path infopath = {
+		.mnt = w->h_ppath.mnt
+	};
+
+	h_dir = d_inode(w->h_ppath.dentry);
+	IMustLock(h_dir);
+
+	err = 0;
+	elm = rev->elm;
+	for (nelm = rev->nelm; nelm > 0; nelm--, elm++) {
+		AuDebugOn(elm->created && elm->info_last);
+		if (elm->created) {
+			AuDbg("here\n");
+			delegated = NULL;
+			infopath.dentry = elm->info_dentry;
+			err = vfsub_unlink(h_dir, &infopath, &delegated,
+					   !w->no_sio);
+			AuTraceErr(err);
+			if (unlikely(err == -EWOULDBLOCK))
+				iput(delegated);
+			dput(elm->info_dentry);
+		} else if (elm->info_last) {
+			AuDbg("here\n");
+			w->fdata->drinfo = *elm->info_last;
+			memcpy(w->fdata->drinfo.oldname,
+			       elm->info_last->oldname,
+			       elm->info_last->oldnamelen);
+			err = au_drinfo_store_sio(w, /*elm*/NULL);
+			au_kfree_rcu(elm->info_last);
+		}
+		if (unlikely(err))
+			AuIOErr("%d, %s\n", err, w->whname);
+		/* go on even if err */
+	}
+}
+
+/* caller has to call au_dr_rename_fin() later */
+/* re-commit later */ __maybe_unused
+static int au_drinfo_store(struct dentry *dentry, aufs_bindex_t btgt,
+			   struct qstr *dst_name, void *_rev)
+{
+	int err, sz, nelm;
+	aufs_bindex_t bindex, btail;
+	struct au_drinfo_store work;
+	struct au_drinfo_rev *rev, **p;
+	struct au_drinfo_rev_elm *elm;
+	struct super_block *sb;
+	struct au_branch *br;
+	struct au_hinode *hdir;
+
+	err = au_drinfo_store_work_init(&work, btgt);
+	AuTraceErr(err);
+	if (unlikely(err))
+		goto out;
+
+	err = -ENOMEM;
+	btail = au_dbtaildir(dentry);
+	nelm = btail - btgt;
+	sz = sizeof(*rev) + sizeof(*elm) * nelm;
+	rev = kcalloc(1, sz, GFP_NOFS);
+	if (unlikely(!rev)) {
+		AuTraceErr(err);
+		goto out_args;
+	}
+	rev->nelm = nelm;
+	elm = rev->elm;
+	p = _rev;
+	*p = rev;
+
+	err = 0;
+	sb = dentry->d_sb;
+	work.h_ppath.dentry = au_h_dptr(dentry, btgt);
+	work.h_ppath.mnt = au_sbr_mnt(sb, btgt);
+	hdir = au_hi(d_inode(dentry), btgt);
+	au_hn_inode_lock_nested(hdir, AuLsc_I_CHILD);
+	for (bindex = btgt + 1; bindex <= btail; bindex++, elm++) {
+		work.h_dentry = au_h_dptr(dentry, bindex);
+		if (!work.h_dentry)
+			continue;
+
+		err = au_drinfo_construct(&work.fdata, work.h_dentry,
+					  &work.allocated);
+		AuTraceErr(err);
+		if (unlikely(err))
+			break;
+
+		work.renameback = au_qstreq(&work.h_dentry->d_name, dst_name);
+		br = au_sbr(sb, bindex);
+		work.whnamelen = sizeof(AUFS_WH_DR_INFO_PFX) - 1;
+		work.whnamelen += au_drinfo_name(br, work.infoname,
+						 work.infonamelen);
+		AuDbg("whname %.*s, i%llu, %.*s\n",
+		      work.whnamelen, work.whname,
+		      be64_to_cpu((__force __be64)work.fdata->drinfo.ino),
+		      work.fdata->drinfo.oldnamelen,
+		      work.fdata->drinfo.oldname);
+
+		err = au_drinfo_store_sio(&work, elm);
+		AuTraceErr(err);
+		if (unlikely(err))
+			break;
+	}
+	if (unlikely(err)) {
+		/* revert all drinfo */
+		au_drinfo_store_rev(rev, &work);
+		au_kfree_try_rcu(rev);
+		*p = NULL;
+	}
+	au_hn_inode_unlock(hdir);
+
+out_args:
+	au_drinfo_store_work_fin(&work);
+out:
+	return err;
+}

include/uapi/linux/aufs_type.h

@@ -88,8 +88,11 @@ typedef int16_t aufs_bindex_t;
 #define AUFS_PLINK_MAINT_DIR	"fs/" AUFS_NAME
 #define AUFS_PLINK_MAINT_PATH	AUFS_PLINK_MAINT_DIR "/" AUFS_PLINK_MAINT_NAME
 
-/* whiteouted doubly */
+/* dirren, renamed dir */
+#define AUFS_DR_INFO_PFX	AUFS_WH_PFX ".dr."
 #define AUFS_DR_BRHINO_NAME	AUFS_WH_PFX "hino"
+/* whiteouted doubly */
+#define AUFS_WH_DR_INFO_PFX	AUFS_WH_PFX AUFS_DR_INFO_PFX
 #define AUFS_WH_DR_BRHINO	AUFS_WH_PFX AUFS_DR_BRHINO_NAME
 
 #define AUFS_DIROPQ_NAME	AUFS_WH_PFX ".opq" /* whiteouted doubly */
@@ -186,4 +189,25 @@ static inline int au_br_wh_linkable(int brperm)
 	return !(brperm & AuBrWAttr_NoLinkWH);
 }
 
+/* ---------------------------------------------------------------------- */
+
+/* dirren. the branch is identified by the filename who contains this */
+struct au_drinfo {
+	uint64_t ino;
+	union {
+		uint8_t oldnamelen;
+		uint64_t _padding;
+	};
+	uint8_t oldname[0];
+} __aligned(8);
+
+struct au_drinfo_fdata {
+	uint32_t magic;
+	struct au_drinfo drinfo;
+} __aligned(8);
+
+#define AUFS_DRINFO_MAGIC_V1	('a' << 24 | 'd' << 16 | 'r' << 8 | 0x01)
+/* future */
+#define AUFS_DRINFO_MAGIC_V2	('a' << 24 | 'd' << 16 | 'r' << 8 | 0x02)
+
 #endif /* __AUFS_TYPE_H__ */