linux - MTD 设备的逻辑删除 block 大小可以增加吗？

Question

jffs2(mtd-utils 版本 1.5.0、mkfs.jffs2 修订版 1.60)的最小删除 block 大小似乎为 8KiB:

Erase size 0x1000 too small. Increasing to 8KiB minimum

但是我正在使用 at25df321a 运​​行 Linux 3.10，

m25p80 spi32766.0: at25df321a (4096 Kbytes),

且删除 block 大小仅为4KiB:

mtd5
Name:                           spi32766.0
Type:                           nor
Eraseblock size:                4096 bytes, 4.0 KiB
Amount of eraseblocks:          1024 (4194304 bytes, 4.0 MiB)
Minimum input/output unit size: 1 byte
Sub-page size:                  1 byte
Character device major/minor:   90:10
Bad blocks are allowed:         false
Device is writable:             true

有没有办法让mtd系统将多个删除 block 视为一个？也许是一些 ioctl 或模块参数？

如果我刷新具有较大删除 block 大小的 jffs2 镜像，我会收到大量内核错误消息、丢失文件，有时还会出现 panic 。

解决方法

我发现，尽管删除 block 大小为 4KiB，但 flasherase --jffs2 仍能生成有效的文件系统。所以我破解了 mkfs.jfss2.c 文件，生成的图像似乎工作正常。我会对其进行一些测试。

diff -rupN orig/mkfs.jffs2.c new/mkfs.jffs2.c
--- orig/mkfs.jffs2.c   2014-10-20 15:43:31.751696500 +0200
+++ new/mkfs.jffs2.c    2014-10-20 15:43:12.623431400 +0200
@@ -1659,11 +1659,11 @@ int main(int argc, char **argv)
                                                  }
                                                  erase_block_size *= units;

-                                                 /* If it's less than 8KiB, they're not allowed */
-                                                 if (erase_block_size < 0x2000) {
-                                                         fprintf(stderr, "Erase size 0x%x too small. Increasing to 8KiB minimum\n",
+                                                 /* If it's less than 4KiB, they're not allowed */
+                                                 if (erase_block_size < 0x1000) {
+                                                         fprintf(stderr, "Erase size 0x%x too small. Increasing to 4KiB minimum\n",
                                                                          erase_block_size);
-                                                         erase_block_size = 0x2000;
+                                                         erase_block_size = 0x1000;
                                                  }
                                                  break;
                                          }

Answer 1

http://lists.infradead.org/pipermail/linux-mtd/2010-September/031876.html

JFFS2 should be able to fit at least one node to eraseblock. The maximum node size is 4KiB+few bytes. This is why the minimum eraseblocks size is 8KiB.

But in practice, even 8KiB is bad because you and up with wasting a lot of space at the end of eraseblocks.

You should join several erasblock into one virtual eraseblock of 64 or 128 KiB and use it - this will be more optimal.

一些驱动程序已经实现了这一点。我知道

MTD_SPI_NOR_USE_4K_SECTORS

Linux 配置选项。必须将其设置为“n”才能启用大小为 0x00010000 的大删除扇区。