[U-Boot] [PATCH v2] ext2load: increase read speed

[Jason Cooper]

This patch dramatically drops the amount of time u-boot needs to read a
file from an ext2 partition.  On a typical 2 to 5 MB file (kernels and
initrds) it goes from tens of seconds to a couple seconds.

All we are doing here is grouping contiguous blocks into one read.

Boot tested on Globalscale Technologies Dreamplug (Kirkwood ARM SoC)
with three different files.  sha1sums were calculated in Linux
userspace, and then confirmed after ext2load.

The following test results were provided by Eric Nelson:

Tested on i.MX6 Sabre Lite board loading a file of ~900k:

Without patch:

      MX6QSABRELITE U-Boot > time ext2load sata 0:1 12000000
/usr/lib/libperl.so.5.12.4 && crc32 12000000 $filesize
      Loading file "/usr/lib/libperl.so.5.12.4" from sata device 0:1
      (hda1)
      958032 bytes read

      time: 0.414 seconds, 414 ticks
      CRC32 for 12000000 ... 120e9e4f ==> 550deec9

With patch:
      MX6QSABRELITE U-Boot > time ext2load sata 0:1 12000000
/usr/lib/libperl.so.5.12.4 && crc32 12000000 $filesize
      Loading file "/usr/lib/libperl.so.5.12.4" from sata device 0:1
      (hda1)
      958032 bytes read

      time: 0.205 seconds, 205 ticks
      CRC32 for 12000000 ... 120e9e4f ==> 550deec9

And, the following results were reported by Thierry Reding:

Before:

      Tegra2 (Medcom) # time ext2load mmc 0 0x17000000 /boot/uImage
      Loading file "/boot/uImage" from mmc device 0:1 (xxa1)
      5609104 bytes read

      time: 4.638 seconds, 4638 ticks
      Tegra2 (Medcom) # crc32 0x17000000 559690
      CRC32 for 17000000 ... 1755968f ==> 158788be

After:

      Tegra2 (Medcom) # time ext2load mmc 0 0x17000000 /boot/uImage
      Loading file "/boot/uImage" from mmc device 0:1 (xxa1)
      5609104 bytes read

      time: 0.317 seconds, 317 ticks
      Tegra2 (Medcom) # crc32 0x17000000 559690
      CRC32 for 17000000 ... 1755968f ==> 158788be

I can also successfully load the loaded uImage to a prompt

End results.

Signed-off-by: Jason Cooper <u-boot at lakedaemon.net>
Tested-by: Eric Nelson <eric.nelson at boundarydevices.com>
Tested-by: Thierry Reding <thierry.reding at avionic-design.de>
---
Changes since v1:
  - updated commit entry to include test results from Eric Nelson and Thierry
    Reding

Based against tag 2012.04.01

 fs/ext2/ext2fs.c |   26 ++++++++++++++++++++++++--
 1 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/fs/ext2/ext2fs.c b/fs/ext2/ext2fs.c
index f621741..f1fce48 100644
--- a/fs/ext2/ext2fs.c
+++ b/fs/ext2/ext2fs.c
@@ -420,7 +420,6 @@ int ext2fs_read_file
 		if (blknr < 0) {
 			return (-1);
 		}
-		blknr = blknr << log2blocksize;
 
 		/* Last block.  */
 		if (i == blockcnt - 1) {
@@ -438,6 +437,29 @@ int ext2fs_read_file
 			blockend -= skipfirst;
 		}
 
+		/* grab middle blocks in one go */
+		if (i != pos / blocksize && i != blockcnt - 1 && blockcnt > 3) {
+			int oldblk = blknr;
+			int blocknxt;
+			while (i < blockcnt - 1) {
+				blocknxt = ext2fs_read_block(node, i + 1);
+				if (blocknxt == (oldblk + 1)) {
+					oldblk = blocknxt;
+					i++;
+				} else {
+					blocknxt = ext2fs_read_block(node, i);
+					break;
+				}
+			}
+
+			if (oldblk == blknr)
+				blockend = blocksize;
+			else
+				blockend = (1 + blocknxt - blknr) * blocksize;
+		}
+
+		blknr = blknr << log2blocksize;
+
 		/* If the block number is 0 this block is not stored on disk but
 		   is zero filled instead.  */
 		if (blknr) {
@@ -450,7 +472,7 @@ int ext2fs_read_file
 		} else {
 			memset (buf, 0, blocksize - skipfirst);
 		}
-		buf += blocksize - skipfirst;
+		buf += blockend - skipfirst;
 	}
 	return (len);
 }
-- 
1.7.3.4