2 files changed, 41 insertions, 4 deletions

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 13b05cb33b08..78ae89488a4f 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -593,6 +593,7 @@ static int attach_by_scanning(struct ubi_device *ubi)
         ubi->good_peb_count = ubi->peb_count - ubi->bad_peb_count;
         ubi->max_ec = si->max_ec;
         ubi->mean_ec = si->mean_ec;
+        ubi_msg("max. sequence number:       %llu", si->max_sqnum);
 
         err = ubi_read_volume_table(ubi, si);
         if (err)
@@ -981,7 +982,7 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
         ubi_msg("number of PEBs reserved for bad PEB handling: %d",
                 ubi->beb_rsvd_pebs);
         ubi_msg("max/mean erase counter: %d/%d", ubi->max_ec, ubi->mean_ec);
-        ubi_msg("image sequence number: %d", ubi->image_seq);
+        ubi_msg("image sequence number:  %d", ubi->image_seq);
 
         /*
          * The below lock makes sure we do not race with 'ubi_thread()' which
diff --git a/drivers/mtd/ubi/eba.c b/drivers/mtd/ubi/eba.c
index b582671ca3a0..fe74749e0dae 100644
--- a/drivers/mtd/ubi/eba.c
+++ b/drivers/mtd/ubi/eba.c
@@ -1166,6 +1166,44 @@ out_unlock_leb:
 }
 
 /**
+ * print_rsvd_warning - warn about not having enough reserved PEBs.
+ * @ubi: UBI device description object
+ *
+ * This is a helper function for 'ubi_eba_init_scan()' which is called when UBI
+ * cannot reserve enough PEBs for bad block handling. This function makes a
+ * decision whether we have to print a warning or not. The algorithm is as
+ * follows:
+ *   o if this is a new UBI image, then just print the warning
+ *   o if this is an UBI image which has already been used for some time, print
+ *     a warning only if we can reserve less than 10% of the expected amount of
+ *     the reserved PEB.
+ *
+ * The idea is that when UBI is used, PEBs become bad, and the reserved pool
+ * of PEBs becomes smaller, which is normal and we do not want to scare users
+ * with a warning every time they attach the MTD device. This was an issue
+ * reported by real users.
+ */
+static void print_rsvd_warning(struct ubi_device *ubi,
+                               struct ubi_scan_info *si)
+{
+        /*
+         * The 1 << 18 (256KiB) number is picked randomly, just a reasonably
+         * large number to distinguish between newly flashed and used images.
+         */
+        if (si->max_sqnum > (1 << 18)) {
+                int min = ubi->beb_rsvd_level / 10;
+
+                if (!min)
+                        min = 1;
+                if (ubi->beb_rsvd_pebs > min)
+                        return;
+        }
+
+        ubi_warn("cannot reserve enough PEBs for bad PEB handling, reserved %d,"
+                 " need %d", ubi->beb_rsvd_pebs, ubi->beb_rsvd_level);
+}
+
+/**
  * ubi_eba_init_scan - initialize the EBA sub-system using scanning information.
  * @ubi: UBI device description object
  * @si: scanning information
@@ -1237,9 +1275,7 @@ int ubi_eba_init_scan(struct ubi_device *ubi, struct ubi_scan_info *si)
                 if (ubi->avail_pebs < ubi->beb_rsvd_level) {
                         /* No enough free physical eraseblocks */
                         ubi->beb_rsvd_pebs = ubi->avail_pebs;
-                        ubi_warn("cannot reserve enough PEBs for bad PEB "
-                                 "handling, reserved %d, need %d",
-                                 ubi->beb_rsvd_pebs, ubi->beb_rsvd_level);
+                        print_rsvd_warning(ubi, si);
                 } else
                         ubi->beb_rsvd_pebs = ubi->beb_rsvd_level;