UBI: introduce the VID buffer concept

Currently, all VID headers are allocated and freed using the
ubi_zalloc_vid_hdr() and ubi_free_vid_hdr() function. These functions
make sure to align allocation on ubi->vid_hdr_alsize and adjust the
vid_hdr pointer to match the ubi->vid_hdr_shift requirements.
This works fine, but is a bit convoluted.
Moreover, the future introduction of LEB consolidation (needed to support
MLC/TLC NANDs) will allows a VID buffer to contain more than one VID
header.

Hence the creation of a ubi_vid_io_buf struct to attach extra information
to the VID header.

We currently only store the actual pointer of the underlying buffer, but
will soon add the number of VID headers contained in the buffer.

Signed-off-by: Boris Brezillon <[e-mail]>
Signed-off-by: Richard Weinberger <[e-mail]>

drivers/mtd/ubi/attach.c

···
 {
 	int len, err, second_is_newer, bitflips = 0, corrupted = 0;
 	uint32_t data_crc, crc;
-	struct ubi_vid_hdr *vh = NULL;
+	struct ubi_vid_io_buf *vidb = NULL;
 	unsigned long long sqnum2 = be64_to_cpu(vid_hdr->sqnum);
 
 	if (sqnum2 == aeb->sqnum) {
···
 			return bitflips << 1;
 		}
 
-		vh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
-		if (!vh)
+		vidb = ubi_alloc_vid_buf(ubi, GFP_KERNEL);
+		if (!vidb)
 			return -ENOMEM;
 
 		pnum = aeb->pnum;
-		err = ubi_io_read_vid_hdr(ubi, pnum, vh, 0);
+		err = ubi_io_read_vid_hdr(ubi, pnum, vidb, 0);
 		if (err) {
 			if (err == UBI_IO_BITFLIPS)
 				bitflips = 1;
···
 			}
 		}
 
-		vid_hdr = vh;
+		vid_hdr = ubi_get_vid_hdr(vidb);
 	}
 
 	/* Read the data of the copy and check the CRC */
···
 	}
 	mutex_unlock(&ubi->buf_mutex);
 
-	ubi_free_vid_hdr(ubi, vh);
+	ubi_free_vid_buf(vidb);
 
 	if (second_is_newer)
 		dbg_bld("second PEB %d is newer, copy_flag is set", pnum);
···
 out_unlock:
 	mutex_unlock(&ubi->buf_mutex);
 out_free_vidh:
-	ubi_free_vid_hdr(ubi, vh);
+	ubi_free_vid_buf(vidb);
 	return err;
 }
 
···
 		    int pnum, bool fast)
 {
 	struct ubi_ec_hdr *ech = ai->ech;
-	struct ubi_vid_hdr *vidh = ai->vidh;
+	struct ubi_vid_io_buf *vidb = ai->vidb;
+	struct ubi_vid_hdr *vidh = ubi_get_vid_hdr(vidb);
 	long long ec;
 	int err, bitflips = 0, vol_id = -1, ec_err = 0;
 
···
 
 	/* OK, we've done with the EC header, let's look at the VID header */
 
-	err = ubi_io_read_vid_hdr(ubi, pnum, vidh, 0);
+	err = ubi_io_read_vid_hdr(ubi, pnum, vidb, 0);
 	if (err < 0)
 		return err;
 	switch (err) {
···
 	if (!ai->ech)
 		return err;
 
-	ai->vidh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
-	if (!ai->vidh)
+	ai->vidb = ubi_alloc_vid_buf(ubi, GFP_KERNEL);
+	if (!ai->vidb)
 		goto out_ech;
 
 	for (pnum = start; pnum < ubi->peb_count; pnum++) {
···
 	if (err)
 		goto out_vidh;
 
-	ubi_free_vid_hdr(ubi, ai->vidh);
+	ubi_free_vid_buf(ai->vidb);
 	kfree(ai->ech);
 
 	return 0;
 
 out_vidh:
-	ubi_free_vid_hdr(ubi, ai->vidh);
+	ubi_free_vid_buf(ai->vidb);
 out_ech:
 	kfree(ai->ech);
 	return err;
···
 	if (!scan_ai->ech)
 		goto out_ai;
 
-	scan_ai->vidh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
-	if (!scan_ai->vidh)
+	scan_ai->vidb = ubi_alloc_vid_buf(ubi, GFP_KERNEL);
+	if (!scan_ai->vidb)
 		goto out_ech;
 
 	for (pnum = 0; pnum < UBI_FM_MAX_START; pnum++) {
···
 			goto out_vidh;
 	}
 
-	ubi_free_vid_hdr(ubi, scan_ai->vidh);
+	ubi_free_vid_buf(scan_ai->vidb);
 	kfree(scan_ai->ech);
 
 	if (scan_ai->force_full_scan)
···
 	return err;
 
 out_vidh:
-	ubi_free_vid_hdr(ubi, scan_ai->vidh);
+	ubi_free_vid_buf(scan_ai->vidb);
 out_ech:
 	kfree(scan_ai->ech);
 out_ai:
···
  */
 static int self_check_ai(struct ubi_device *ubi, struct ubi_attach_info *ai)
 {
-	struct ubi_vid_hdr *vidh = ai->vidh;
+	struct ubi_vid_io_buf *vidb = ai->vidb;
+	struct ubi_vid_hdr *vidh = ubi_get_vid_hdr(vidb);
 	int pnum, err, vols_found = 0;
 	struct rb_node *rb1, *rb2;
 	struct ubi_ainf_volume *av;
···
 
 			last_aeb = aeb;
 
-			err = ubi_io_read_vid_hdr(ubi, aeb->pnum, vidh, 1);
+			err = ubi_io_read_vid_hdr(ubi, aeb->pnum, vidb, 1);
 			if (err && err != UBI_IO_BITFLIPS) {
 				ubi_err(ubi, "VID header is not OK (%d)",
 					err);

drivers/mtd/ubi/eba.c

···
 		     void *buf, int offset, int len, int check)
 {
 	int err, pnum, scrub = 0, vol_id = vol->vol_id;
+	struct ubi_vid_io_buf *vidb;
 	struct ubi_vid_hdr *vid_hdr;
 	uint32_t uninitialized_var(crc);
 
···
 
 retry:
 	if (check) {
-		vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
-		if (!vid_hdr) {
+		vidb = ubi_alloc_vid_buf(ubi, GFP_NOFS);
+		if (!vidb) {
 			err = -ENOMEM;
 			goto out_unlock;
 		}
 
-		err = ubi_io_read_vid_hdr(ubi, pnum, vid_hdr, 1);
+		vid_hdr = ubi_get_vid_hdr(vidb);
+
+		err = ubi_io_read_vid_hdr(ubi, pnum, vidb, 1);
 		if (err && err != UBI_IO_BITFLIPS) {
 			if (err > 0) {
 				/*
···
 		ubi_assert(len == be32_to_cpu(vid_hdr->data_size));
 
 		crc = be32_to_cpu(vid_hdr->data_crc);
-		ubi_free_vid_hdr(ubi, vid_hdr);
+		ubi_free_vid_buf(vidb);
 	}
 
 	err = ubi_io_read_data(ubi, buf, pnum, offset, len);
···
 	return err;
 
 out_free:
-	ubi_free_vid_hdr(ubi, vid_hdr);
+	ubi_free_vid_buf(vidb);
 out_unlock:
 	leb_read_unlock(ubi, vol_id, lnum);
 	return err;
···
  * @buf: data which was not written because of the write failure
  * @offset: offset of the failed write
  * @len: how many bytes should have been written
- * @vid: VID header
+ * @vidb: VID buffer
  * @retry: whether the caller should retry in case of failure
  *
  * This function is called in case of a write failure and moves all good data
···
  */
 static int try_recover_peb(struct ubi_volume *vol, int pnum, int lnum,
 			   const void *buf, int offset, int len,
-			   struct ubi_vid_hdr *vid_hdr, bool *retry)
+			   struct ubi_vid_io_buf *vidb, bool *retry)
 {
 	struct ubi_device *ubi = vol->ubi;
+	struct ubi_vid_hdr *vid_hdr;
 	int new_pnum, err, vol_id = vol->vol_id, data_size;
 	uint32_t crc;
 
···
 	ubi_msg(ubi, "recover PEB %d, move data to PEB %d",
 		pnum, new_pnum);
 
-	err = ubi_io_read_vid_hdr(ubi, pnum, vid_hdr, 1);
+	err = ubi_io_read_vid_hdr(ubi, pnum, vidb, 1);
 	if (err && err != UBI_IO_BITFLIPS) {
 		if (err > 0)
 			err = -EIO;
···
 	vid_hdr->copy_flag = 1;
 	vid_hdr->data_size = cpu_to_be32(data_size);
 	vid_hdr->data_crc = cpu_to_be32(crc);
-	err = ubi_io_write_vid_hdr(ubi, new_pnum, vid_hdr);
+	err = ubi_io_write_vid_hdr(ubi, new_pnum, vidb);
 	if (err)
 		goto out_unlock;
 
···
 {
 	int err, idx = vol_id2idx(ubi, vol_id), tries;
 	struct ubi_volume *vol = ubi->volumes[idx];
-	struct ubi_vid_hdr *vid_hdr;
+	struct ubi_vid_io_buf *vidb;
 
-	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
-	if (!vid_hdr)
+	vidb = ubi_alloc_vid_buf(ubi, GFP_NOFS);
+	if (!vidb)
 		return -ENOMEM;
 
 	for (tries = 0; tries <= UBI_IO_RETRIES; tries++) {
 		bool retry;
 
-		err = try_recover_peb(vol, pnum, lnum, buf, offset, len,
-				      vid_hdr, &retry);
+		err = try_recover_peb(vol, pnum, lnum, buf, offset, len, vidb,
+				      &retry);
 		if (!err || !retry)
 			break;
 
 		ubi_msg(ubi, "try again");
 	}
 
-	ubi_free_vid_hdr(ubi, vid_hdr);
+	ubi_free_vid_buf(vidb);
 
 	return err;
 }
···
  * try_write_vid_and_data - try to write VID header and data to a new PEB.
  * @vol: volume description object
  * @lnum: logical eraseblock number
- * @vid_hdr: VID header to write
+ * @vidb: the VID buffer to write
  * @buf: buffer containing the data
  * @offset: where to start writing data
  * @len: how many bytes should be written
···
  * flash media, but may be some garbage.
  */
 static int try_write_vid_and_data(struct ubi_volume *vol, int lnum,
-				  struct ubi_vid_hdr *vid_hdr, const void *buf,
+				  struct ubi_vid_io_buf *vidb, const void *buf,
 				  int offset, int len)
 {
 	struct ubi_device *ubi = vol->ubi;
···
 	dbg_eba("write VID hdr and %d bytes at offset %d of LEB %d:%d, PEB %d",
 		len, offset, vol_id, lnum, pnum);
 
-	err = ubi_io_write_vid_hdr(ubi, pnum, vid_hdr);
+	err = ubi_io_write_vid_hdr(ubi, pnum, vidb);
 	if (err) {
 		ubi_warn(ubi, "failed to write VID header to LEB %d:%d, PEB %d",
 			 vol_id, lnum, pnum);
···
 		      const void *buf, int offset, int len)
 {
 	int err, pnum, tries, vol_id = vol->vol_id;
+	struct ubi_vid_io_buf *vidb;
 	struct ubi_vid_hdr *vid_hdr;
 
 	if (ubi->ro_mode)
···
 	 * The logical eraseblock is not mapped. We have to get a free physical
 	 * eraseblock and write the volume identifier header there first.
 	 */
-	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
-	if (!vid_hdr) {
+	vidb = ubi_alloc_vid_buf(ubi, GFP_NOFS);
+	if (!vidb) {
 		leb_write_unlock(ubi, vol_id, lnum);
 		return -ENOMEM;
 	}
+
+	vid_hdr = ubi_get_vid_hdr(vidb);
 
 	vid_hdr->vol_type = UBI_VID_DYNAMIC;
 	vid_hdr->sqnum = cpu_to_be64(ubi_next_sqnum(ubi));
···
 	vid_hdr->data_pad = cpu_to_be32(vol->data_pad);
 
 	for (tries = 0; tries <= UBI_IO_RETRIES; tries++) {
-		err = try_write_vid_and_data(vol, lnum, vid_hdr, buf, offset,
-					     len);
+		err = try_write_vid_and_data(vol, lnum, vidb, buf, offset, len);
 		if (err != -EIO || !ubi->bad_allowed)
 			break;
 
···
 		ubi_msg(ubi, "try another PEB");
 	}
 
-	ubi_free_vid_hdr(ubi, vid_hdr);
+	ubi_free_vid_buf(vidb);
 
 out:
 	if (err)
···
 			 int lnum, const void *buf, int len, int used_ebs)
 {
 	int err, tries, data_size = len, vol_id = vol->vol_id;
+	struct ubi_vid_io_buf *vidb;
 	struct ubi_vid_hdr *vid_hdr;
 	uint32_t crc;
 
···
 	else
 		ubi_assert(!(len & (ubi->min_io_size - 1)));
 
-	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
-	if (!vid_hdr)
+	vidb = ubi_alloc_vid_buf(ubi, GFP_NOFS);
+	if (!vidb)
 		return -ENOMEM;
+
+	vid_hdr = ubi_get_vid_hdr(vidb);
 
 	err = leb_write_lock(ubi, vol_id, lnum);
 	if (err)
···
 	ubi_assert(vol->eba_tbl->entries[lnum].pnum < 0);
 
 	for (tries = 0; tries <= UBI_IO_RETRIES; tries++) {
-		err = try_write_vid_and_data(vol, lnum, vid_hdr, buf, 0, len);
+		err = try_write_vid_and_data(vol, lnum, vidb, buf, 0, len);
 		if (err != -EIO || !ubi->bad_allowed)
 			break;
 
···
 	leb_write_unlock(ubi, vol_id, lnum);
 
 out:
-	ubi_free_vid_hdr(ubi, vid_hdr);
+	ubi_free_vid_buf(vidb);
 
 	return err;
 }
···
 			      int lnum, const void *buf, int len)
 {
 	int err, tries, vol_id = vol->vol_id;
+	struct ubi_vid_io_buf *vidb;
 	struct ubi_vid_hdr *vid_hdr;
 	uint32_t crc;
 
···
 		return ubi_eba_write_leb(ubi, vol, lnum, NULL, 0, 0);
 	}
 
-	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
-	if (!vid_hdr)
+	vidb = ubi_alloc_vid_buf(ubi, GFP_NOFS);
+	if (!vidb)
 		return -ENOMEM;
+
+	vid_hdr = ubi_get_vid_hdr(vidb);
 
 	mutex_lock(&ubi->alc_mutex);
 	err = leb_write_lock(ubi, vol_id, lnum);
···
 	dbg_eba("change LEB %d:%d", vol_id, lnum);
 
 	for (tries = 0; tries <= UBI_IO_RETRIES; tries++) {
-		err = try_write_vid_and_data(vol, lnum, vid_hdr, buf, 0, len);
+		err = try_write_vid_and_data(vol, lnum, vidb, buf, 0, len);
 		if (err != -EIO || !ubi->bad_allowed)
 			break;
 
···
 
 out_mutex:
 	mutex_unlock(&ubi->alc_mutex);
-	ubi_free_vid_hdr(ubi, vid_hdr);
+	ubi_free_vid_buf(vidb);
 	return err;
 }
 
···
  *   o a negative error code in case of failure.
  */
 int ubi_eba_copy_leb(struct ubi_device *ubi, int from, int to,
-		     struct ubi_vid_hdr *vid_hdr)
+		     struct ubi_vid_io_buf *vidb)
 {
 	int err, vol_id, lnum, data_size, aldata_size, idx;
+	struct ubi_vid_hdr *vid_hdr = ubi_get_vid_hdr(vidb);
 	struct ubi_volume *vol;
 	uint32_t crc;
 
···
 	}
 	vid_hdr->sqnum = cpu_to_be64(ubi_next_sqnum(ubi));
 
-	err = ubi_io_write_vid_hdr(ubi, to, vid_hdr);
+	err = ubi_io_write_vid_hdr(ubi, to, vidb);
 	if (err) {
 		if (err == -EIO)
 			err = MOVE_TARGET_WR_ERR;
···
 	cond_resched();
 
 	/* Read the VID header back and check if it was written correctly */
-	err = ubi_io_read_vid_hdr(ubi, to, vid_hdr, 1);
+	err = ubi_io_read_vid_hdr(ubi, to, vidb, 1);
 	if (err) {
 		if (err != UBI_IO_BITFLIPS) {
 			ubi_warn(ubi, "error %d while reading VID header back from PEB %d",

drivers/mtd/ubi/fastmap.c

···
  * Returns a new struct ubi_vid_hdr on success.
  * NULL indicates out of memory.
  */
-static struct ubi_vid_hdr *new_fm_vhdr(struct ubi_device *ubi, int vol_id)
+static struct ubi_vid_io_buf *new_fm_vbuf(struct ubi_device *ubi, int vol_id)
 {
-	struct ubi_vid_hdr *new;
+	struct ubi_vid_io_buf *new;
+	struct ubi_vid_hdr *vh;
 
-	new = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
+	new = ubi_alloc_vid_buf(ubi, GFP_KERNEL);
 	if (!new)
 		goto out;
 
-	new->vol_type = UBI_VID_DYNAMIC;
-	new->vol_id = cpu_to_be32(vol_id);
+	vh = ubi_get_vid_hdr(new);
+	vh->vol_type = UBI_VID_DYNAMIC;
+	vh->vol_id = cpu_to_be32(vol_id);
 
 	/* UBI implementations without fastmap support have to delete the
 	 * fastmap.
 	 */
-	new->compat = UBI_COMPAT_DELETE;
+	vh->compat = UBI_COMPAT_DELETE;
 
 out:
 	return new;
···
 		     __be32 *pebs, int pool_size, unsigned long long *max_sqnum,
 		     struct list_head *free)
 {
+	struct ubi_vid_io_buf *vb;
 	struct ubi_vid_hdr *vh;
 	struct ubi_ec_hdr *ech;
 	struct ubi_ainf_peb *new_aeb;
···
 	if (!ech)
 		return -ENOMEM;
 
-	vh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
-	if (!vh) {
+	vb = ubi_alloc_vid_buf(ubi, GFP_KERNEL);
+	if (!vb) {
 		kfree(ech);
 		return -ENOMEM;
 	}
+
+	vh = ubi_get_vid_hdr(vb);
 
 	dbg_bld("scanning fastmap pool: size = %i", pool_size);
 
···
 			goto out;
 		}
 
-		err = ubi_io_read_vid_hdr(ubi, pnum, vh, 0);
+		err = ubi_io_read_vid_hdr(ubi, pnum, vb, 0);
 		if (err == UBI_IO_FF || err == UBI_IO_FF_BITFLIPS) {
 			unsigned long long ec = be64_to_cpu(ech->ec);
 			unmap_peb(ai, pnum);
···
 	}
 
 out:
-	ubi_free_vid_hdr(ubi, vh);
+	ubi_free_vid_buf(vb);
 	kfree(ech);
 	return ret;
 }
···
 		     struct ubi_attach_info *scan_ai)
 {
 	struct ubi_fm_sb *fmsb, *fmsb2;
+	struct ubi_vid_io_buf *vb;
 	struct ubi_vid_hdr *vh;
 	struct ubi_ec_hdr *ech;
 	struct ubi_fastmap_layout *fm;
···
 		goto free_fm_sb;
 	}
 
-	vh = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
-	if (!vh) {
+	vb = ubi_alloc_vid_buf(ubi, GFP_KERNEL);
+	if (!vb) {
 		ret = -ENOMEM;
 		goto free_hdr;
 	}
+
+	vh = ubi_get_vid_hdr(vb);
 
 	for (i = 0; i < used_blocks; i++) {
 		int image_seq;
···
 			goto free_hdr;
 		}
 
-		ret = ubi_io_read_vid_hdr(ubi, pnum, vh, 0);
+		ret = ubi_io_read_vid_hdr(ubi, pnum, vb, 0);
 		if (ret && ret != UBI_IO_BITFLIPS) {
 			ubi_err(ubi, "unable to read fastmap block# %i (PEB: %i)",
 				i, pnum);
···
 	ubi->fm_disabled = 0;
 	ubi->fast_attach = 1;
 
-	ubi_free_vid_hdr(ubi, vh);
+	ubi_free_vid_buf(vb);
 	kfree(ech);
 out:
 	up_write(&ubi->fm_protect);
···
 	return ret;
 
 free_hdr:
-	ubi_free_vid_hdr(ubi, vh);
+	ubi_free_vid_buf(vb);
 	kfree(ech);
 free_fm_sb:
 	kfree(fmsb);
···
 	struct ubi_fm_eba *feba;
 	struct ubi_wl_entry *wl_e;
 	struct ubi_volume *vol;
+	struct ubi_vid_io_buf *avbuf, *dvbuf;
 	struct ubi_vid_hdr *avhdr, *dvhdr;
 	struct ubi_work *ubi_wrk;
 	struct rb_node *tmp_rb;
···
 	fm_raw = ubi->fm_buf;
 	memset(ubi->fm_buf, 0, ubi->fm_size);
 
-	avhdr = new_fm_vhdr(ubi, UBI_FM_SB_VOLUME_ID);
-	if (!avhdr) {
+	avbuf = new_fm_vbuf(ubi, UBI_FM_SB_VOLUME_ID);
+	if (!avbuf) {
 		ret = -ENOMEM;
 		goto out;
 	}
 
-	dvhdr = new_fm_vhdr(ubi, UBI_FM_DATA_VOLUME_ID);
-	if (!dvhdr) {
+	dvbuf = new_fm_vbuf(ubi, UBI_FM_DATA_VOLUME_ID);
+	if (!dvbuf) {
 		ret = -ENOMEM;
 		goto out_kfree;
 	}
+
+	avhdr = ubi_get_vid_hdr(avbuf);
+	dvhdr = ubi_get_vid_hdr(dvbuf);
 
 	seen_pebs = init_seen(ubi);
 	if (IS_ERR(seen_pebs)) {
···
 	spin_unlock(&ubi->volumes_lock);
 
 	dbg_bld("writing fastmap SB to PEB %i", new_fm->e[0]->pnum);
-	ret = ubi_io_write_vid_hdr(ubi, new_fm->e[0]->pnum, avhdr);
+	ret = ubi_io_write_vid_hdr(ubi, new_fm->e[0]->pnum, avbuf);
 	if (ret) {
 		ubi_err(ubi, "unable to write vid_hdr to fastmap SB!");
 		goto out_kfree;
···
 		dvhdr->lnum = cpu_to_be32(i);
 		dbg_bld("writing fastmap data to PEB %i sqnum %llu",
 			new_fm->e[i]->pnum, be64_to_cpu(dvhdr->sqnum));
-		ret = ubi_io_write_vid_hdr(ubi, new_fm->e[i]->pnum, dvhdr);
+		ret = ubi_io_write_vid_hdr(ubi, new_fm->e[i]->pnum, dvbuf);
 		if (ret) {
 			ubi_err(ubi, "unable to write vid_hdr to PEB %i!",
 				new_fm->e[i]->pnum);
···
 	dbg_bld("fastmap written!");
 
 out_kfree:
-	ubi_free_vid_hdr(ubi, avhdr);
-	ubi_free_vid_hdr(ubi, dvhdr);
+	ubi_free_vid_buf(avbuf);
+	ubi_free_vid_buf(dvbuf);
 	free_seen(seen_pebs);
 out:
 	return ret;
···
 	int ret;
 	struct ubi_fastmap_layout *fm;
 	struct ubi_wl_entry *e;
-	struct ubi_vid_hdr *vh = NULL;
+	struct ubi_vid_io_buf *vb = NULL;
+	struct ubi_vid_hdr *vh;
 
 	if (!ubi->fm)
 		return 0;
···
 	if (!fm)
 		goto out;
 
-	vh = new_fm_vhdr(ubi, UBI_FM_SB_VOLUME_ID);
-	if (!vh)
+	vb = new_fm_vbuf(ubi, UBI_FM_SB_VOLUME_ID);
+	if (!vb)
 		goto out_free_fm;
+
+	vh = ubi_get_vid_hdr(vb);
 
 	ret = -ENOSPC;
 	e = ubi_wl_get_fm_peb(ubi, 1);
···
 	 * to scanning mode.
 	 */
 	vh->sqnum = cpu_to_be64(ubi_next_sqnum(ubi));
-	ret = ubi_io_write_vid_hdr(ubi, e->pnum, vh);
+	ret = ubi_io_write_vid_hdr(ubi, e->pnum, vb);
 	if (ret < 0) {
 		ubi_wl_put_fm_peb(ubi, e, 0, 0);
 		goto out_free_fm;
···
 	ubi->fm = fm;
 
 out:
-	ubi_free_vid_hdr(ubi, vh);
+	ubi_free_vid_buf(vb);
 	return ret;
 
 out_free_fm:

drivers/mtd/ubi/io.c

···
 	loff_t addr;
 	uint32_t data = 0;
 	struct ubi_ec_hdr ec_hdr;
+	struct ubi_vid_io_buf vidb;
 
 	/*
 	 * Note, we cannot generally define VID header buffers on stack,
···
 			goto error;
 	}
 
-	err = ubi_io_read_vid_hdr(ubi, pnum, &vid_hdr, 0);
+	ubi_init_vid_buf(ubi, &vidb, &vid_hdr);
+	ubi_assert(&vid_hdr == ubi_get_vid_hdr(&vidb));
+
+	err = ubi_io_read_vid_hdr(ubi, pnum, &vidb, 0);
 	if (err != UBI_IO_BAD_HDR_EBADMSG && err != UBI_IO_BAD_HDR &&
 	    err != UBI_IO_FF){
 		addr += ubi->vid_hdr_aloffset;
···
  * ubi_io_read_vid_hdr - read and check a volume identifier header.
  * @ubi: UBI device description object
  * @pnum: physical eraseblock number to read from
- * @vid_hdr: &struct ubi_vid_hdr object where to store the read volume
- * identifier header
+ * @vidb: the volume identifier buffer to store data in
  * @verbose: be verbose if the header is corrupted or wasn't found
  *
  * This function reads the volume identifier header from physical eraseblock
- * @pnum and stores it in @vid_hdr. It also checks CRC checksum of the read
+ * @pnum and stores it in @vidb. It also checks CRC checksum of the read
  * volume identifier header. The error codes are the same as in
  * 'ubi_io_read_ec_hdr()'.
  *
···
  * 'ubi_io_read_ec_hdr()', so refer commentaries in 'ubi_io_read_ec_hdr()'.
  */
 int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
-			struct ubi_vid_hdr *vid_hdr, int verbose)
+			struct ubi_vid_io_buf *vidb, int verbose)
 {
 	int err, read_err;
 	uint32_t crc, magic, hdr_crc;
-	void *p;
+	struct ubi_vid_hdr *vid_hdr = ubi_get_vid_hdr(vidb);
+	void *p = vidb->buffer;
 
 	dbg_io("read VID header from PEB %d", pnum);
 	ubi_assert(pnum >= 0 &&  pnum < ubi->peb_count);
 
-	p = (char *)vid_hdr - ubi->vid_hdr_shift;
 	read_err = ubi_io_read(ubi, p, pnum, ubi->vid_hdr_aloffset,
 			  ubi->vid_hdr_shift + UBI_VID_HDR_SIZE);
 	if (read_err && read_err != UBI_IO_BITFLIPS && !mtd_is_eccerr(read_err))
···
  * ubi_io_write_vid_hdr - write a volume identifier header.
  * @ubi: UBI device description object
  * @pnum: the physical eraseblock number to write to
- * @vid_hdr: the volume identifier header to write
+ * @vidb: the volume identifier buffer to write
  *
  * This function writes the volume identifier header described by @vid_hdr to
  * physical eraseblock @pnum. This function automatically fills the
- * @vid_hdr->magic and the @vid_hdr->version fields, as well as calculates
- * header CRC checksum and stores it at vid_hdr->hdr_crc.
+ * @vidb->hdr->magic and the @vidb->hdr->version fields, as well as calculates
+ * header CRC checksum and stores it at vidb->hdr->hdr_crc.
  *
  * This function returns zero in case of success and a negative error code in
  * case of failure. If %-EIO is returned, the physical eraseblock probably went
  * bad.
  */
 int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
-			 struct ubi_vid_hdr *vid_hdr)
+			 struct ubi_vid_io_buf *vidb)
 {
+	struct ubi_vid_hdr *vid_hdr = ubi_get_vid_hdr(vidb);
 	int err;
 	uint32_t crc;
-	void *p;
+	void *p = vidb->buffer;
 
 	dbg_io("write VID header to PEB %d", pnum);
 	ubi_assert(pnum >= 0 &&  pnum < ubi->peb_count);
···
 	if (ubi_dbg_power_cut(ubi, POWER_CUT_VID_WRITE))
 		return -EROFS;
 
-	p = (char *)vid_hdr - ubi->vid_hdr_shift;
 	err = ubi_io_write(ubi, p, pnum, ubi->vid_hdr_aloffset,
 			   ubi->vid_hdr_alsize);
 	return err;
···
 {
 	int err;
 	uint32_t crc, hdr_crc;
+	struct ubi_vid_io_buf *vidb;
 	struct ubi_vid_hdr *vid_hdr;
 	void *p;
 
 	if (!ubi_dbg_chk_io(ubi))
 		return 0;
 
-	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
-	if (!vid_hdr)
+	vidb = ubi_alloc_vid_buf(ubi, GFP_NOFS);
+	if (!vidb)
 		return -ENOMEM;
 
-	p = (char *)vid_hdr - ubi->vid_hdr_shift;
+	vid_hdr = ubi_get_vid_hdr(vidb);
+	p = vidb->buffer;
 	err = ubi_io_read(ubi, p, pnum, ubi->vid_hdr_aloffset,
 			  ubi->vid_hdr_alsize);
 	if (err && err != UBI_IO_BITFLIPS && !mtd_is_eccerr(err))
···
 	err = self_check_vid_hdr(ubi, pnum, vid_hdr);
 
 exit:
-	ubi_free_vid_hdr(ubi, vid_hdr);
+	ubi_free_vid_buf(vidb);
 	return err;
 }
 

drivers/mtd/ubi/ubi.h

···
 };
 
 /**
+ * struct ubi_vid_io_buf - VID buffer used to read/write VID info to/from the
+ *			   flash.
+ * @hdr: a pointer to the VID header stored in buffer
+ * @buffer: underlying buffer
+ */
+struct ubi_vid_io_buf {
+	struct ubi_vid_hdr *hdr;
+	void *buffer;
+};
+
+/**
  * struct ubi_wl_entry - wear-leveling entry.
  * @u.rb: link in the corresponding (free/used) RB-tree
  * @u.list: link in the protection queue
···
  * @ec_count: a temporary variable used when calculating @mean_ec
  * @aeb_slab_cache: slab cache for &struct ubi_ainf_peb objects
  * @ech: temporary EC header. Only available during scan
- * @vidh: temporary VID header. Only available during scan
+ * @vidh: temporary VID buffer. Only available during scan
  *
  * This data structure contains the result of attaching an MTD device and may
  * be used by other UBI sub-systems to build final UBI data structures, further
···
 	int ec_count;
 	struct kmem_cache *aeb_slab_cache;
 	struct ubi_ec_hdr *ech;
-	struct ubi_vid_hdr *vidh;
+	struct ubi_vid_io_buf *vidb;
 };
 
 /**
···
 int ubi_eba_atomic_leb_change(struct ubi_device *ubi, struct ubi_volume *vol,
 			      int lnum, const void *buf, int len);
 int ubi_eba_copy_leb(struct ubi_device *ubi, int from, int to,
-		     struct ubi_vid_hdr *vid_hdr);
+		     struct ubi_vid_io_buf *vidb);
 int ubi_eba_init(struct ubi_device *ubi, struct ubi_attach_info *ai);
 unsigned long long ubi_next_sqnum(struct ubi_device *ubi);
 int self_check_eba(struct ubi_device *ubi, struct ubi_attach_info *ai_fastmap,
···
 int ubi_io_write_ec_hdr(struct ubi_device *ubi, int pnum,
 			struct ubi_ec_hdr *ec_hdr);
 int ubi_io_read_vid_hdr(struct ubi_device *ubi, int pnum,
-			struct ubi_vid_hdr *vid_hdr, int verbose);
+			struct ubi_vid_io_buf *vidb, int verbose);
 int ubi_io_write_vid_hdr(struct ubi_device *ubi, int pnum,
-			 struct ubi_vid_hdr *vid_hdr);
+			 struct ubi_vid_io_buf *vidb);
 
 /* build.c */
 int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
···
 }
 
 /**
- * ubi_zalloc_vid_hdr - allocate a volume identifier header object.
- * @ubi: UBI device description object
- * @gfp_flags: GFP flags to allocate with
- *
- * This function returns a pointer to the newly allocated and zero-filled
- * volume identifier header object in case of success and %NULL in case of
- * failure.
+ * ubi_init_vid_buf - Initialize a VID buffer
+ * @ubi: the UBI device
+ * @vidb: the VID buffer to initialize
+ * @buf: the underlying buffer
  */
-static inline struct ubi_vid_hdr *
-ubi_zalloc_vid_hdr(const struct ubi_device *ubi, gfp_t gfp_flags)
+static inline void ubi_init_vid_buf(const struct ubi_device *ubi,
+				    struct ubi_vid_io_buf *vidb,
+				    void *buf)
 {
-	void *vid_hdr;
+	if (buf)
+		memset(buf, 0, ubi->vid_hdr_alsize);
 
-	vid_hdr = kzalloc(ubi->vid_hdr_alsize, gfp_flags);
-	if (!vid_hdr)
-		return NULL;
-
-	/*
-	 * VID headers may be stored at un-aligned flash offsets, so we shift
-	 * the pointer.
-	 */
-	return vid_hdr + ubi->vid_hdr_shift;
+	vidb->buffer = buf;
+	vidb->hdr = buf + ubi->vid_hdr_shift;
 }
 
 /**
- * ubi_free_vid_hdr - free a volume identifier header object.
- * @ubi: UBI device description object
- * @vid_hdr: the object to free
+ * ubi_init_vid_buf - Allocate a VID buffer
+ * @ubi: the UBI device
+ * @gfp_flags: GFP flags to use for the allocation
  */
-static inline void ubi_free_vid_hdr(const struct ubi_device *ubi,
-				    struct ubi_vid_hdr *vid_hdr)
+static inline struct ubi_vid_io_buf *
+ubi_alloc_vid_buf(const struct ubi_device *ubi, gfp_t gfp_flags)
 {
-	void *p = vid_hdr;
+	struct ubi_vid_io_buf *vidb;
+	void *buf;
 
-	if (!p)
+	vidb = kzalloc(sizeof(*vidb), gfp_flags);
+	if (!vidb)
+		return NULL;
+
+	buf = kmalloc(ubi->vid_hdr_alsize, gfp_flags);
+	if (!buf) {
+		kfree(vidb);
+		return NULL;
+	}
+
+	ubi_init_vid_buf(ubi, vidb, buf);
+
+	return vidb;
+}
+
+/**
+ * ubi_free_vid_buf - Free a VID buffer
+ * @vidb: the VID buffer to free
+ */
+static inline void ubi_free_vid_buf(struct ubi_vid_io_buf *vidb)
+{
+	if (!vidb)
 		return;
 
-	kfree(p - ubi->vid_hdr_shift);
+	kfree(vidb->buffer);
+	kfree(vidb);
+}
+
+/**
+ * ubi_get_vid_hdr - Get the VID header attached to a VID buffer
+ * @vidb: VID buffer
+ */
+static inline struct ubi_vid_hdr *ubi_get_vid_hdr(struct ubi_vid_io_buf *vidb)
+{
+	return vidb->hdr;
 }
 
 /*

drivers/mtd/ubi/vtbl.c

···
 		       int copy, void *vtbl)
 {
 	int err, tries = 0;
+	struct ubi_vid_io_buf *vidb;
 	struct ubi_vid_hdr *vid_hdr;
 	struct ubi_ainf_peb *new_aeb;
 
 	dbg_gen("create volume table (copy #%d)", copy + 1);
 
-	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_KERNEL);
-	if (!vid_hdr)
+	vidb = ubi_alloc_vid_buf(ubi, GFP_KERNEL);
+	if (!vidb)
 		return -ENOMEM;
+
+	vid_hdr = ubi_get_vid_hdr(vidb);
 
 retry:
 	new_aeb = ubi_early_get_peb(ubi, ai);
···
 	vid_hdr->sqnum = cpu_to_be64(++ai->max_sqnum);
 
 	/* The EC header is already there, write the VID header */
-	err = ubi_io_write_vid_hdr(ubi, new_aeb->pnum, vid_hdr);
+	err = ubi_io_write_vid_hdr(ubi, new_aeb->pnum, vidb);
 	if (err)
 		goto write_error;
 
···
 	 */
 	err = ubi_add_to_av(ubi, ai, new_aeb->pnum, new_aeb->ec, vid_hdr, 0);
 	ubi_free_aeb(ai, new_aeb);
-	ubi_free_vid_hdr(ubi, vid_hdr);
+	ubi_free_vid_buf(vidb);
 	return err;
 
 write_error:
···
 	}
 	ubi_free_aeb(ai, new_aeb);
 out_free:
-	ubi_free_vid_hdr(ubi, vid_hdr);
+	ubi_free_vid_buf(vidb);
 	return err;
 
 }

drivers/mtd/ubi/wl.c

···
 	int anchor = wrk->anchor;
 #endif
 	struct ubi_wl_entry *e1, *e2;
+	struct ubi_vid_io_buf *vidb;
 	struct ubi_vid_hdr *vid_hdr;
 	int dst_leb_clean = 0;
 
···
 	if (shutdown)
 		return 0;
 
-	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
-	if (!vid_hdr)
+	vidb = ubi_alloc_vid_buf(ubi, GFP_NOFS);
+	if (!vidb)
 		return -ENOMEM;
+
+	vid_hdr = ubi_get_vid_hdr(vidb);
 
 	mutex_lock(&ubi->move_mutex);
 	spin_lock(&ubi->wl_lock);
···
 	 * which is being moved was unmapped.
 	 */
 
-	err = ubi_io_read_vid_hdr(ubi, e1->pnum, vid_hdr, 0);
+	err = ubi_io_read_vid_hdr(ubi, e1->pnum, vidb, 0);
 	if (err && err != UBI_IO_BITFLIPS) {
 		dst_leb_clean = 1;
 		if (err == UBI_IO_FF) {
···
 	vol_id = be32_to_cpu(vid_hdr->vol_id);
 	lnum = be32_to_cpu(vid_hdr->lnum);
 
-	err = ubi_eba_copy_leb(ubi, e1->pnum, e2->pnum, vid_hdr);
+	err = ubi_eba_copy_leb(ubi, e1->pnum, e2->pnum, vidb);
 	if (err) {
 		if (err == MOVE_CANCEL_RACE) {
 			/*
···
 	if (scrubbing)
 		ubi_msg(ubi, "scrubbed PEB %d (LEB %d:%d), data moved to PEB %d",
 			e1->pnum, vol_id, lnum, e2->pnum);
-	ubi_free_vid_hdr(ubi, vid_hdr);
+	ubi_free_vid_buf(vidb);
 
 	spin_lock(&ubi->wl_lock);
 	if (!ubi->move_to_put) {
···
 	ubi->wl_scheduled = 0;
 	spin_unlock(&ubi->wl_lock);
 
-	ubi_free_vid_hdr(ubi, vid_hdr);
+	ubi_free_vid_buf(vidb);
 	if (dst_leb_clean) {
 		ensure_wear_leveling(ubi, 1);
 	} else {
···
 	ubi->move_to_put = ubi->wl_scheduled = 0;
 	spin_unlock(&ubi->wl_lock);
 
-	ubi_free_vid_hdr(ubi, vid_hdr);
+	ubi_free_vid_buf(vidb);
 	wl_entry_destroy(ubi, e1);
 	wl_entry_destroy(ubi, e2);
 
···
 	ubi->wl_scheduled = 0;
 	spin_unlock(&ubi->wl_lock);
 	mutex_unlock(&ubi->move_mutex);
-	ubi_free_vid_hdr(ubi, vid_hdr);
+	ubi_free_vid_buf(vidb);
 	return 0;
 }