From 9b4b0d9f9f9ad2febd1b94dc0c8c7411bf0eb167 Mon Sep 17 00:00:00 2001 From: MITSUNARI Shigeo Date: Thu, 25 Oct 2012 12:14:36 +1100 Subject: [PATCH] fs/block_dev.c: page cache wrongly left invalidated after revalidate_disk() We found that bdev->bd_invalidated was left set once revalidate_disk() is called, which results in page cache flush every time that device is open. Specifically, we found this problem in MD block device. Once we resize a MD device, mdadm --monitor periodically flush all page cache for that device every 60 or 1000 seconds when it opens the device. This bug lies since at least 3.2.0 till the latest kernel(3.6.2). Patch is attached. The following steps will reproduce the problem. 1. prepair a block device(ex. /dev/sdb). 2. create two partitions. sudo parted /dev/sdb mklabel gpt mkpart primary 0% 50% mkpart primary 50% 100% 3. create a md device. sudo mdadm -C /dev/md/hoge -l 1 -n 2 -e 1.2 --assume-clean --auto=md \ --symlink=no /dev/sdb1 /dev/sdb2 4. create file system and mount it sudo mkfs.ext3 /dev/md/hoge sudo mkdir /mnt/test sudo mount /dev/md/hoge /mnt/test 5. try to resize the device sudo mdadm -G /dev/md/hoge --size=max 6. create a file to fill file cache. sudo dd if=/dev/urandom of=/mnt/test/data bs=1M count=10 and verity the current status of file by free command. 7. mdadm monitor will open the md device every 1000 seconds and you will find all file cache on the device are cleared. The timing can be reduced by the following steps. a) kill mdadm and restart it with --delay option /sbin/mdadm --monitor --delay=30 --pid-file /var/run/mdadm/monitor.pid \ --daemonise --scan --syslog or open the md device directly. sudo dd if=/dev/md/hoge of=/dev/null bs=4096 count=1 Signed-off-by: MITSUNARI Shigeo Cc: Al Viro Cc: Jeff Moyer Cc: Signed-off-by: Andrew Morton --- fs/block_dev.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/block_dev.c b/fs/block_dev.c index b3c1d3dae77d..729a98b59f2d 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -1073,6 +1073,7 @@ int revalidate_disk(struct gendisk *disk) mutex_lock(&bdev->bd_mutex); check_disk_size_change(disk, bdev); + bdev->bd_invalidated = 0; mutex_unlock(&bdev->bd_mutex); bdput(bdev); return ret; -- 2.39.5