diff mbox

[v2,2/2] btrfs-progs: limit the min value of total_bytes

Message ID 1348801360-1851-2-git-send-email-robin.k.dong@gmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

Robin Dong Sept. 28, 2012, 3:02 a.m. UTC 
From: Robin Dong <sanbai@taobao.com>

Using mkfs.btrfs like:

        mkfs.btrfs -b 1048576 /dev/sda

will report error:

	mkfs.btrfs: volumes.c:796: btrfs_alloc_chunk: Assertion `!(ret)' failed.
	Aborted

because the length of dev_extent is 4MB.

But if we use mkfs.btrfs with 8MB total bytes, the newly mounted btrfs filesystem
would not contain even one empty file. So 12MB will be good min-value for block_count.

Signed-off-by: Robin Dong <sanbai@taobao.com>
---
 mkfs.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

Comments

David Sterba Sept. 30, 2012, 11:05 p.m. UTC | #1 
On Fri, Sep 28, 2012 at 11:02:40AM +0800, Robin Dong wrote:
> From: Robin Dong <sanbai@taobao.com>
> 
> Using mkfs.btrfs like:
> 
>         mkfs.btrfs -b 1048576 /dev/sda
> 
> will report error:
> 
> 	mkfs.btrfs: volumes.c:796: btrfs_alloc_chunk: Assertion `!(ret)' failed.
> 	Aborted
> 
> because the length of dev_extent is 4MB.
> 
> But if we use mkfs.btrfs with 8MB total bytes, the newly mounted btrfs filesystem
> would not contain even one empty file. So 12MB will be good min-value for block_count.

I'm not able to create a single file even on a 12MB filesystem
(with -d single -m single --mixed), so any limit that would let the mkfs
finish normally should be fine. For the single/single case it's 5MB but
for the dup/dup it's 156MB. It's due to the known bug in the blockgroup
creation with multiple devices (applies on dup as well here) that leads
to:

# btrfs fi df .
System, DUP: total=8.00MB, used=4.00KB
System: total=4.00MB, used=0.00
Data+Metadata, DUP: total=64.00MB, used=24.00KB
Data+Metadata: total=8.00MB, used=0.00

8*2 + 4 + 64*2 + 8 = 156

so, 12M is too small to avoid the mkfs crash.

david
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Robin Dong Oct. 8, 2012, 7:10 a.m. UTC | #2 
2012/10/1 David Sterba <dave@jikos.cz>:
> On Fri, Sep 28, 2012 at 11:02:40AM +0800, Robin Dong wrote:
>> From: Robin Dong <sanbai@taobao.com>
>>
>> Using mkfs.btrfs like:
>>
>>         mkfs.btrfs -b 1048576 /dev/sda
>>
>> will report error:
>>
>>       mkfs.btrfs: volumes.c:796: btrfs_alloc_chunk: Assertion `!(ret)' failed.
>>       Aborted
>>
>> because the length of dev_extent is 4MB.
>>
>> But if we use mkfs.btrfs with 8MB total bytes, the newly mounted btrfs filesystem
>> would not contain even one empty file. So 12MB will be good min-value for block_count.
>
> I'm not able to create a single file even on a 12MB filesystem
> (with -d single -m single --mixed), so any limit that would let the mkfs
> finish normally should be fine. For the single/single case it's 5MB but
> for the dup/dup it's 156MB. It's due to the known bug in the blockgroup
> creation with multiple devices (applies on dup as well here) that leads
> to:
>
> # btrfs fi df .
> System, DUP: total=8.00MB, used=4.00KB
> System: total=4.00MB, used=0.00
> Data+Metadata, DUP: total=64.00MB, used=24.00KB
> Data+Metadata: total=8.00MB, used=0.00
>
> 8*2 + 4 + 64*2 + 8 = 156
>
> so, 12M is too small to avoid the mkfs crash.

Thanks for your notice!
>
> david
diff mbox

Patch

diff --git a/mkfs.c b/mkfs.c
index 8420482..496faa8 100644
--- a/mkfs.c
+++ b/mkfs.c
@@ -1345,7 +1345,11 @@  int main(int ac, char **av)
 				&dev_block_count, &mixed, nodiscard);
 		if (block_count == 0)
 			block_count = dev_block_count;
-		else if (block_count > dev_block_count) {
+		else if (block_count < 3 * BTRFS_MKFS_SYSTEM_GROUP_SIZE) {
+			fprintf(stderr, "Illegal total number of bytes %u\n",
+					block_count);
+			exit(1);
+		} else if (block_count > dev_block_count) {
 			fprintf(stderr, "%s is smaller than requested size\n", file);
 			exit(1);
 		}