UBIFS: fix available blocks count

Take into account that 2 eraseblocks are never available because
they are reserved for the index. This gives more realistic count
of FS blocks.

To avoid future confusions like this, introduce a constant.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

3 files changed, 13 insertions, 9 deletions

diff --git a/fs/ubifs/budget.c b/fs/ubifs/budget.c
index d5a65037e172..e42342547001 100644
--- a/fs/ubifs/budget.c
+++ b/fs/ubifs/budget.c
@@ -280,13 +280,8 @@ int ubifs_calc_min_idx_lebs(struct ubifs_info *c)
          * extra LEB to compensate.
          */
         ret += 1;
-        /*
-         * At present the index needs at least 2 LEBs: one for the index head
-         * and one for in-the-gaps method (which currently does not cater for
-         * the index head and so excludes it from consideration).
-         */
-        if (ret < 2)
-                ret = 2;
+        if (ret < MIN_INDEX_LEBS)
+                ret = MIN_INDEX_LEBS;
         return ret;
 }
 
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 2dbaa4fc2cbb..a6a7798d020b 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -695,9 +695,10 @@ static int init_constants_late(struct ubifs_info *c)
          * necessary to report something for the 'statfs()' call.
          *
          * Subtract the LEB reserved for GC, the LEB which is reserved for
-         * deletions, and assume only one journal head is available.
+         * deletions, minimum LEBs for the index, and assume only one journal
+         * head is available.
          */
-        tmp64 = c->main_lebs - 2 - c->jhead_cnt + 1;
+        tmp64 = c->main_lebs - 1 - 1 - MIN_INDEX_LEBS - c->jhead_cnt + 1;
         tmp64 *= (uint64_t)c->leb_size - c->leb_overhead;
         tmp64 = ubifs_reported_space(c, tmp64);
         c->block_cnt = tmp64 >> UBIFS_BLOCK_SHIFT;
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index f8ef7c1def1f..543e850022eb 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -63,6 +63,14 @@
 #define SQNUM_WARN_WATERMARK 0xFFFFFFFF00000000ULL
 #define SQNUM_WATERMARK      0xFFFFFFFFFF000000ULL
 
+/*
+ * Minimum amount of LEBs reserved for the index. At present the index needs at
+ * least 2 LEBs: one for the index head and one for in-the-gaps method (which
+ * currently does not cater for the index head and so excludes it from
+ * consideration).
+ */
+#define MIN_INDEX_LEBS 2
+
 /* Minimum amount of data UBIFS writes to the flash */
 #define MIN_WRITE_SZ (UBIFS_DATA_NODE_SZ + 8)