On Wed, 09 Apr 2008 17:29:42 -0600 Andrew Patterson <andrew.patterson@xxxxxx> wrote: > I ran into this problem while trying to resize a mounted file-system > after growing/shrinking the size of the underlying block device (in this > case, a fibre-channel LUN). The kernel recognizes the device size change > when revalidate_disk() is called, but the bdev->bd_inode->i_size will > not be updated for any new openers if there are already openers of the > device. In my case I was using LVM thusly: > > 1. Create a volume group with a physical volume on something that > can be resized (usually some sort of SCSI RAID device). > 2. Create a logical volume on that VG. This holds the underlying > PV block device open as long at the LV is activated > 3. Run blockdev --getsize <block dev> > 4. Resize the underlying block device. > 5. Get the OS to notice the change. For fibre-channel LUN's you > can use /sys/class/scsi_device/<device>/device/rescan. > 6. Size is correctly changed in /dev/block/<device>/size > 7. Run blockdev --getsize again (no change in size reported) > 8. Inactivate the LV (there are now no longer any openers on the > block device) > 9. Run blockdev --getsize again. Size is now correct as there are > no openers on the device when blockdev is run. > > This problem has been reported before at: > > http://lkml.org/lkml/2007/7/3/83 > > The following patch is a suggestion on how to fix this problem. It is > not a complete solution as it is probably a bad thing to change other > openers device size without at least protecting the change with a lock. > And user-apps and other sub-systems might not like the reported device > size being changed underneath them. It looks like the following > sub-systems access this value: > > ndb > dm > md > affs > hfs > jfs > reiserfs > udf > > > Subject: [PATCH] Reset bdev size regardless of other openers. > > A block device may be resized while online. If the revalidate_disk > routine is called after the resize, the gendisk->capacity value is > updated for the device. However, the bdev->bd_inode->i_size is not > updated when the block device is opened if there are any other openers > on the device. This means that apps like LVM are unlikely to see the > size change as they tend to keep their block devices open. There is a > discussion of this problem at: > > http://lkml.org/lkml/2007/7/3/83 > > This patch changes block_dev.c:do_open() to call bd_set_size() > regardless if there are other openers on the device. It should not be > applied in its existing state as changing i_size should be protected by > a lock. Also, there needs to be some analysis on the effects of changing > the device size underneath an app. > > Andrew Patterson > > Subject: [PATCH] Reset bdev size regardless of other openers. > > A block device may be resized while online. If the revalidate_disk > routine is called after the resize, the gendisk->capacity value is > updated for the device. However, the bdev->bd_inode->i_size is not > updated when the block device is opened if there are any other openers > on the device. This means that apps like LVM are unlikely to see the > size change as they tend to keep their block devices open. There is a > discussion of this problem at: > > http://lkml.org/lkml/2007/7/3/83 > > This patch changes block_dev.c:do_open() to call bd_set_size() > regardless if there are other openers on the device. It should not be > applied in its existing state as changing i_size should be protected by > a lock. Also, there needs to be some analysis on the effects of changing > the device size underneath an app. hm, tricky. I don't know what problems a change like this might cause - probably few, given the rarity and slowness of block device resizing. Presumably increasing the device size will cause les problems than decreasing it would. Do we even support device shrinking? > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 7d822fa..d13a4e5 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -992,6 +992,9 @@ static int do_open(struct block_device *bdev, struct file *file, int for_part) > ret = bdev->bd_disk->fops->open(bdev->bd_inode, file); > if (ret) > goto out; > + /* device may have been resized with revalidate_disk */ > + if (!part) > + bd_set_size(bdev, (loff_t)get_capacity(disk)<<9); > } > if (bdev->bd_invalidated) > rescan_partitions(bdev->bd_disk, bdev); I'd have thought that an appropriate way to fix all this would be to perform the i_size update between freeze_bdev() and thaw_bdev(), when the fs is quiesced. But it's not really in my comfort zone. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
