Attachment 317391 Details for Bug 454872 – call flush_disk after detecting an online resize

[patch] call flush_disk after detecting an online resize

6-call-flush_disk-after-detecting-an-online-resize.patch (text/plain), 2.16 KB, created by Jeff Moyer on 2008-09-22 17:39:37 UTC

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Creator: Jeff Moyer

Created: 2008-09-22 17:39:37 UTC

Size: 2.16 KB

patch

obsolete

>Call flush_disk() after detecting an online resize.
>
>We call flush_disk() to make sure the buffer cache for the disk is
>flushed after a disk resize. There are two resize cases, growing and
>shrinking. Given that users can shrink/then grow a disk before
>revalidate_disk() is called, we treat the grow case identically to
>shrinking. We need to flush the buffer cache after an online shrink
>because, as James Bottomley puts it,
>
>     The two use cases for shrinking I can see are
>
>     1. planned: the fs is already shrunk to within the new boundaries
>        and all data is relocated, so invalidate is fine (any dirty
>        buffers that might exist in the shrunk region are there only
>        because they were relocated but not yet written to their
>        original location).
>     2. unplanned:  In this case, the fs is probably toast, so whether
>        we invalidate or not isn't going to make a whole lot of
>        difference; it's still going to try to read or write from
>        sectors beyond the new size and get I/O errors.
>
>Immediately invalidating shrunk disks will cause errors for outstanding
>I/Os for reads/write beyond the new end of the disk to be generated
>earlier then if we waited for the normal buffer cache operation. It also
>removes a potential security hole where we might keep old data around
>from beyond the end of the shrunk disk if the disk was not invalidated.
>
>diff -up linux-2.6.9/fs/block_dev.c.orig linux-2.6.9/fs/block_dev.c
>--- linux-2.6.9/fs/block_dev.c.orig	2008-09-22 13:18:26.334730795 -0400
>+++ linux-2.6.9/fs/block_dev.c	2008-09-22 13:19:45.054729788 -0400
>@@ -528,8 +528,8 @@ static void flush_disk(struct block_devi
> 
> 		if (bdev->bd_disk)
> 			disk_name(bdev->bd_disk, 0, name);
>-		printk(KERN_WARNING "VFS: busy inodes on changed media %s\n",
>-		       name);
>+		printk(KERN_WARNING "VFS: busy inodes on changed media or "
>+		       "resized disk %s\n", name);
> 	}
> 
> 	if (!bdev->bd_disk)
>@@ -562,6 +562,7 @@ void check_disk_size_change(struct gendi
> 		       "%s: detected capacity change from %lld to %lld\n",
> 		       name, bdev_size, disk_size);
> 		i_size_write(bdev->bd_inode, disk_size);
>+		flush_disk(bdev);
> 	}
> }
> EXPORT_SYMBOL(check_disk_size_change);

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Attachments on bug 454872: 317386 | 317387 | 317388 | 317389 | 317390 | 317391