/ sd-extは仕事中に唯一の読み取り専用の読み取りを再開します -- external-sd フィールド と app2sd フィールド と mount フィールド と s2e フィールド android 関連 問題

I have an HTC Desire with cyanogenmod 7.2 (with pdroid patch) and with an partitioned microSD card (first: FAT, second: ext3).

The second partition gets automatically mounted read/writeable as /sd-ext as it should be. I'm using S2E to store my apps and the app data on this ext3 partition. The mount command shows me that the ext3 partition is not only mounted to /sd-ext but also to /data/app and /data/data. All of them are mounted read/writeable.

My first question: Is it normal and secure that multiple directories are bound to the same partition? Are there no conflicts?

In the beginning everything worked fine. I could install and use my apps without problems. But after a while more and more apps begun to crash and I always had to restart my phone to get rid of those crashes again. I discovered that the crashes where caused by a read only data partition. In fact all the directories /sd-ext, /data/data, and /data/apps where suddenly mounted read only.

My second question: Why does Android sometimes remount my ext3 partition in read only mode while I work with my phone?

Remounting as read-only is an action taken by Linux-based operating systems (including Android) in case of errors accessing the filesystem. In this case it probably indicates that your micro-SD has been (partially) corrupted. There are several possible causes of corruption like this:

• Using the phone as a USB mass storage device and unplugging it while a write is in progress
• The phone rebooting while an app or the OS is writing to the filesystem
• A bug in the ext3 driver in the ROM you're using
• A physical error on the SD card due to excessive heat or cold, mechanical shock, manufacturing defects, strong magnetic fields, &c.

Whatever the root cause, try plugging your card into a card reader on a PC and checking it for filesystem errors (for example, using fsck on a GNU/Linux box).

I finally managed to get rid of the filesystem corruptions. I configured S2E so that it mounts the ext3 partition only to /sd-ext and /data/apps. Since then the partition is not remounted read only anymore. So it seems that the simultaneous write access to the different mount points of the ext3 partition (/data/apps and /data/data) caused the filesystem corruptions.