FAILED: patch "[PATCH] ubi: fastmap: Correctly handle interrupted erasures in EBA" failed to apply to 4.4-stable tree

index 250e30fac61b..593a4f9d97e3 100644
@@ -490,6 +490,82 @@ int ubi_eba_unmap_leb(struct ubi_device *ubi, struct ubi_volume *vol,
 	return err;
 }
 
+#ifdef CONFIG_MTD_UBI_FASTMAP
+/**
+ * check_mapping - check and fixup a mapping
+ * @ubi: UBI device description object
+ * @vol: volume description object
+ * @lnum: logical eraseblock number
+ * @pnum: physical eraseblock number
+ *
+ * Checks whether a given mapping is valid. Fastmap cannot track LEB unmap
+ * operations, if such an operation is interrupted the mapping still looks
+ * good, but upon first read an ECC is reported to the upper layer.
+ * Normaly during the full-scan at attach time this is fixed, for Fastmap
+ * we have to deal with it while reading.
+ * If the PEB behind a LEB shows this symthom we change the mapping to
+ * %UBI_LEB_UNMAPPED and schedule the PEB for erasure.
+ *
+ * Returns 0 on success, negative error code in case of failure.
+ */
+static int check_mapping(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
+			 int *pnum)
+{
+	int err;
+	struct ubi_vid_io_buf *vidb;
+
+	if (!ubi->fast_attach)
+		return 0;
+
+	vidb = ubi_alloc_vid_buf(ubi, GFP_NOFS);
+	if (!vidb)
+		return -ENOMEM;
+
+	err = ubi_io_read_vid_hdr(ubi, *pnum, vidb, 0);
+	if (err > 0 && err != UBI_IO_BITFLIPS) {
+		int torture = 0;
+
+		switch (err) {
+			case UBI_IO_FF:
+			case UBI_IO_FF_BITFLIPS:
+			case UBI_IO_BAD_HDR:
+			case UBI_IO_BAD_HDR_EBADMSG:
+				break;
+			default:
+				ubi_assert(0);
+		}
+
+		if (err == UBI_IO_BAD_HDR_EBADMSG || err == UBI_IO_FF_BITFLIPS)
+			torture = 1;
+
+		down_read(&ubi->fm_eba_sem);
+		vol->eba_tbl->entries[lnum].pnum = UBI_LEB_UNMAPPED;
+		up_read(&ubi->fm_eba_sem);
+		ubi_wl_put_peb(ubi, vol->vol_id, lnum, *pnum, torture);
+
+		*pnum = UBI_LEB_UNMAPPED;
+	} else if (err < 0) {
+		ubi_err(ubi, "unable to read VID header back from PEB %i: %i",
+			*pnum, err);
+
+		goto out_free;
+	}
+
+	err = 0;
+
+out_free:
+	ubi_free_vid_buf(vidb);
+
+	return err;
+}
+#else
+static int check_mapping(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
+		  int *pnum)
+{
+	return 0;
+}
+#endif
+
 /**
  * ubi_eba_read_leb - read data.
  * @ubi: UBI device description object

@@ -522,7 +598,13 @@ int ubi_eba_read_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
 		return err;
 
 	pnum = vol->eba_tbl->entries[lnum].pnum;
-	if (pnum < 0) {
+	if (pnum >= 0) {
+		err = check_mapping(ubi, vol, lnum, &pnum);
+		if (err < 0)
+			goto out_unlock;
+	}
+
+	if (pnum == UBI_LEB_UNMAPPED) {
 		/*
 		 * The logical eraseblock is not mapped, fill the whole buffer
 		 * with 0xFF bytes. The exception is static volumes for which

@@ -930,6 +1012,12 @@ int ubi_eba_write_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
 		return err;
 
 	pnum = vol->eba_tbl->entries[lnum].pnum;
+	if (pnum >= 0) {
+		err = check_mapping(ubi, vol, lnum, &pnum);
+		if (err < 0)
+			goto out;
+	}
+
 	if (pnum >= 0) {
 		dbg_eba("write %d bytes at offset %d of LEB %d:%d, PEB %d",
 			len, offset, vol_id, lnum, pnum);

index 4dd0391d2942..c4a25c858c07 100644
@@ -350,6 +350,82 @@ out_unlock:
 	return err;
 }
 
+#ifdef CONFIG_MTD_UBI_FASTMAP
+/**
+ * check_mapping - check and fixup a mapping
+ * @ubi: UBI device description object
+ * @vol: volume description object
+ * @lnum: logical eraseblock number
+ * @pnum: physical eraseblock number
+ *
+ * Checks whether a given mapping is valid. Fastmap cannot track LEB unmap
+ * operations, if such an operation is interrupted the mapping still looks
+ * good, but upon first read an ECC is reported to the upper layer.
+ * Normaly during the full-scan at attach time this is fixed, for Fastmap
+ * we have to deal with it while reading.
+ * If the PEB behind a LEB shows this symthom we change the mapping to
+ * %UBI_LEB_UNMAPPED and schedule the PEB for erasure.
+ *
+ * Returns 0 on success, negative error code in case of failure.
+ */
+static int check_mapping(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
+			 int *pnum)
+{
+	int err;
+	struct ubi_vid_hdr *vid_hdr;
+
+	if (!ubi->fast_attach)
+		return 0;
+
+	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
+	if (!vid_hdr)
+		return -ENOMEM;
+
+	err = ubi_io_read_vid_hdr(ubi, *pnum, vid_hdr, 0);
+	if (err > 0 && err != UBI_IO_BITFLIPS) {
+		int torture = 0;
+
+		switch (err) {
+			case UBI_IO_FF:
+			case UBI_IO_FF_BITFLIPS:
+			case UBI_IO_BAD_HDR:
+			case UBI_IO_BAD_HDR_EBADMSG:
+				break;
+			default:
+				ubi_assert(0);
+		}
+
+		if (err == UBI_IO_BAD_HDR_EBADMSG || err == UBI_IO_FF_BITFLIPS)
+			torture = 1;
+
+		down_read(&ubi->fm_eba_sem);
+		vol->eba_tbl[lnum] = UBI_LEB_UNMAPPED;
+		up_read(&ubi->fm_eba_sem);
+		ubi_wl_put_peb(ubi, vol->vol_id, lnum, *pnum, torture);
+
+		*pnum = UBI_LEB_UNMAPPED;
+	} else if (err < 0) {
+		ubi_err(ubi, "unable to read VID header back from PEB %i: %i",
+			*pnum, err);
+
+		goto out_free;
+	}
+
+	err = 0;
+
+out_free:
+	ubi_free_vid_hdr(ubi, vid_hdr);
+
+	return err;
+}
+#else
+static int check_mapping(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
+		  int *pnum)
+{
+	return 0;
+}
+#endif
+
 /**
  * ubi_eba_read_leb - read data.
  * @ubi: UBI device description object

@@ -381,7 +457,13 @@ int ubi_eba_read_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
 		return err;
 
 	pnum = vol->eba_tbl[lnum];
-	if (pnum < 0) {
+	if (pnum >= 0) {
+		err = check_mapping(ubi, vol, lnum, &pnum);
+		if (err < 0)
+			goto out_unlock;
+	}
+
+	if (pnum == UBI_LEB_UNMAPPED) {
 		/*
 		 * The logical eraseblock is not mapped, fill the whole buffer
 		 * with 0xFF bytes. The exception is static volumes for which

@@ -696,6 +778,14 @@ int ubi_eba_write_leb(struct ubi_device *ubi, struct ubi_volume *vol, int lnum,
 		return err;
 
 	pnum = vol->eba_tbl[lnum];
+	if (pnum >= 0) {
+		err = check_mapping(ubi, vol, lnum, &pnum);
+		if (err < 0) {
+			leb_write_unlock(ubi, vol_id, lnum);
+			return err;
+		}
+	}
+
 	if (pnum >= 0) {
 		dbg_eba("write %d bytes at offset %d of LEB %d:%d, PEB %d",
 			len, offset, vol_id, lnum, pnum);