UBIFS: introduce a helpful variable

This patch introduces a helpful @c->idx_leb_size variable.
The patch also fixes some spelling issues and makes comments
use "LEB" instead of "eraseblock", which is more correct.
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/budget.c

@@ -194,29 +194,26 @@ static int make_free_space(struct ubifs_info *c)
 }
 
 /**
- * ubifs_calc_min_idx_lebs - calculate amount of eraseblocks for the index.
+ * ubifs_calc_min_idx_lebs - calculate amount of LEBs for the index.
  * @c: UBIFS file-system description object
  *
- * This function calculates and returns the number of eraseblocks which should
- * be kept for index usage.
+ * This function calculates and returns the number of LEBs which should be kept
+ * for index usage.
  */
 int ubifs_calc_min_idx_lebs(struct ubifs_info *c)
 {
-	int idx_lebs, eff_leb_size = c->leb_size - c->max_idx_node_sz;
+	int idx_lebs;
 	long long idx_size;
 
 	idx_size = c->old_idx_sz + c->budg_idx_growth + c->budg_uncommitted_idx;
-
 	/* And make sure we have thrice the index size of space reserved */
-	idx_size = idx_size + (idx_size << 1);
-
+	idx_size += idx_size << 1;
 	/*
 	 * We do not maintain 'old_idx_size' as 'old_idx_lebs'/'old_idx_bytes'
 	 * pair, nor similarly the two variables for the new index size, so we
 	 * have to do this costly 64-bit division on fast-path.
 	 */
-	idx_size += eff_leb_size - 1;
-	idx_lebs = div_u64(idx_size, eff_leb_size);
+	idx_lebs = div_u64(idx_size + c->idx_leb_size - 1, c->idx_leb_size);
 	/*
 	 * The index head is not available for the in-the-gaps method, so add an
 	 * extra LEB to compensate.
@@ -310,15 +307,15 @@ static int can_use_rp(struct ubifs_info *c)
  * do_budget_space - reserve flash space for index and data growth.
  * @c: UBIFS file-system description object
  *
- * This function makes sure UBIFS has enough free eraseblocks for index growth
- * and data.
+ * This function makes sure UBIFS has enough free LEBs for index growth and
+ * data.
  *
  * When budgeting index space, UBIFS reserves thrice as many LEBs as the index
  * would take if it was consolidated and written to the flash. This guarantees
  * that the "in-the-gaps" commit method always succeeds and UBIFS will always
  * be able to commit dirty index. So this function basically adds amount of
  * budgeted index space to the size of the current index, multiplies this by 3,
- * and makes sure this does not exceed the amount of free eraseblocks.
+ * and makes sure this does not exceed the amount of free LEBs.
  *
  * Notes about @c->min_idx_lebs and @c->lst.idx_lebs variables:
  * o @c->lst.idx_lebs is the number of LEBs the index currently uses. It might
@@ -695,12 +692,12 @@ long long ubifs_reported_space(const struct ubifs_info *c, long long free)
  * This function calculates amount of free space to report to user-space.
  *
  * Because UBIFS may introduce substantial overhead (the index, node headers,
- * alignment, wastage at the end of eraseblocks, etc), it cannot report real
- * amount of free flash space it has (well, because not all dirty space is
- * reclaimable, UBIFS does not actually know the real amount). If UBIFS did so,
- * it would bread user expectations about what free space is. Users seem to
- * accustomed to assume that if the file-system reports N bytes of free space,
- * they would be able to fit a file of N bytes to the FS. This almost works for
+ * alignment, wastage at the end of LEBs, etc), it cannot report real amount of
+ * free flash space it has (well, because not all dirty space is reclaimable,
+ * UBIFS does not actually know the real amount). If UBIFS did so, it would
+ * bread user expectations about what free space is. Users seem to accustomed
+ * to assume that if the file-system reports N bytes of free space, they would
+ * be able to fit a file of N bytes to the FS. This almost works for
  * traditional file-systems, because they have way less overhead than UBIFS.
  * So, to keep users happy, UBIFS tries to take the overhead into account.
  */

fs/ubifs/sb.c

@@ -623,7 +623,6 @@ int ubifs_read_superblock(struct ubifs_info *c)
 	c->main_lebs = c->leb_cnt - UBIFS_SB_LEBS - UBIFS_MST_LEBS;
 	c->main_lebs -= c->log_lebs + c->lpt_lebs + c->orph_lebs;
 	c->main_first = c->leb_cnt - c->main_lebs;
-	c->report_rp_size = ubifs_reported_space(c, c->rp_size);
 
 	err = validate_sb(c, sup);
 out:

fs/ubifs/super.c

@@ -700,6 +700,8 @@ static int init_constants_sb(struct ubifs_info *c)
 	if (err)
 		return err;
 
+	/* Initialize effective LEB size used in budgeting calculations */
+	c->idx_leb_size = c->leb_size - c->max_idx_node_sz;
 	return 0;
 }
 
@@ -716,6 +718,7 @@ static void init_constants_master(struct ubifs_info *c)
 	long long tmp64;
 
 	c->min_idx_lebs = ubifs_calc_min_idx_lebs(c);
+	c->report_rp_size = ubifs_reported_space(c, c->rp_size);
 
 	/*
 	 * Calculate total amount of FS blocks. This number is not used

fs/ubifs/ubifs.h

@@ -1015,6 +1015,8 @@ struct ubifs_debug_info;
  * @min_io_shift: number of bits in @min_io_size minus one
  * @leb_size: logical eraseblock size in bytes
  * @half_leb_size: half LEB size
+ * @idx_leb_size: how many bytes of an LEB are effectively available when it is
+ *                used to store indexing nodes (@leb_size - @max_idx_node_sz)
  * @leb_cnt: count of logical eraseblocks
  * @max_leb_cnt: maximum count of logical eraseblocks
  * @old_leb_cnt: count of logical eraseblocks before re-size
@@ -1132,8 +1134,8 @@ struct ubifs_debug_info;
  *             previous commit start
  * @uncat_list: list of un-categorized LEBs
  * @empty_list: list of empty LEBs
- * @freeable_list: list of freeable non-index LEBs (free + dirty == leb_size)
- * @frdi_idx_list: list of freeable index LEBs (free + dirty == leb_size)
+ * @freeable_list: list of freeable non-index LEBs (free + dirty == @leb_size)
+ * @frdi_idx_list: list of freeable index LEBs (free + dirty == @leb_size)
  * @freeable_cnt: number of freeable LEBs in @freeable_list
  *
  * @ltab_lnum: LEB number of LPT's own lprops table
@@ -1253,6 +1255,7 @@ struct ubifs_info {
 	int min_io_shift;
 	int leb_size;
 	int half_leb_size;
+	int idx_leb_size;
 	int leb_cnt;
 	int max_leb_cnt;
 	int old_leb_cnt;