UBIFS: incorporate maximum write size

Incorporate maximum write size into the UBIFS description data
structure. This patch just introduces new 'c->max_write_size'
and 'c->max_write_shift' fields as a preparation for the following
patches.

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

2 files changed, 24 insertions, 0 deletions

diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 703a62109cf2..efc327b92f98 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -507,6 +507,8 @@ static int init_constants_early(struct ubifs_info *c)
         c->half_leb_size = c->leb_size / 2;
         c->min_io_size = c->di.min_io_size;
         c->min_io_shift = fls(c->min_io_size) - 1;
+        c->max_write_size = c->di.max_write_size;
+        c->max_write_shift = fls(c->max_write_size) - 1;
 
         if (c->leb_size < UBIFS_MIN_LEB_SZ) {
                 ubifs_err("too small LEBs (%d bytes), min. is %d bytes",
@@ -526,6 +528,18 @@ static int init_constants_early(struct ubifs_info *c)
         }
 
         /*
+         * Maximum write size has to be greater or equivalent to min. I/O
+         * size, and be multiple of min. I/O size.
+         */
+        if (c->max_write_size < c->min_io_size ||
+            c->max_write_size % c->min_io_size ||
+            !is_power_of_2(c->max_write_size)) {
+                ubifs_err("bad write buffer size %d for %d min. I/O unit",
+                          c->max_write_size, c->min_io_size);
+                return -EINVAL;
+        }
+
+        /*
          * UBIFS aligns all node to 8-byte boundary, so to make function in
          * io.c simpler, assume minimum I/O unit size to be 8 bytes if it is
          * less than 8.
@@ -533,6 +547,10 @@ static int init_constants_early(struct ubifs_info *c)
         if (c->min_io_size < 8) {
                 c->min_io_size = 8;
                 c->min_io_shift = 3;
+                if (c->max_write_size < c->min_io_size) {
+                        c->max_write_size = c->min_io_size;
+                        c->max_write_shift = c->min_io_shift;
+                }
         }
 
         c->ref_node_alsz = ALIGN(UBIFS_REF_NODE_SZ, c->min_io_size);
@@ -1391,6 +1409,7 @@ static int mount_ubifs(struct ubifs_info *c)
 
         dbg_msg("compiled on:         " __DATE__ " at " __TIME__);
         dbg_msg("min. I/O unit size:  %d bytes", c->min_io_size);
+        dbg_msg("max. write size:     %d bytes", c->max_write_size);
         dbg_msg("LEB size:            %d bytes (%d KiB)",
                 c->leb_size, c->leb_size >> 10);
         dbg_msg("data journal heads:  %d",
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index d1823541f987..8b519499f14a 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -1024,6 +1024,9 @@ struct ubifs_debug_info;
  *
  * @min_io_size: minimal input/output unit size
  * @min_io_shift: number of bits in @min_io_size minus one
+ * @max_write_size: maximum amount of bytes the underlying flash can write at a
+ *                  time (MTD write buffer size)
+ * @max_write_shift: number of bits in @max_write_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
@@ -1270,6 +1273,8 @@ struct ubifs_info {
 
         int min_io_size;
         int min_io_shift;
+        int max_write_size;
+        int max_write_shift;
         int leb_size;
         int half_leb_size;
         int idx_leb_size;