On 2022/12/29 22:12, Heinrich Schuchardt wrote:
On 12/28/22 21:51, Sam Winchenbach wrote:
Hello,
Hello, I have hit the following situation when trying to load files
from a BTRFS partition with duplication enabled.
You mean multi-device?
For DUP/RAID1 duplication, they don't have stripe limitation at all.
Thus I believe you're talking about RAID0 (which doesn't have any
duplication/extra mirrors) or RAID10 or RAID5/6?
But for now, we don't support multi-device in U-boot yet, thus I'm not
sure what situation you're talking about.
Mind to run the following command?
# btrfs fi usage <mnt of the btrfs>
In the first example I read a 16KiB file - __btrfs_map_block() changes
the length to something larger than the file being read. This works
fine, as length is later clamped to the file size.
In the second example, __btrfs_map_block() changes the length
parameter to something smaller than the file (the size of a stripe).
This seems to break this check here:
read = len;
num_copies = btrfs_num_copies(fs_info, logical, len);
for (i = 1; i <= num_copies; i++) {
ret = read_extent_data(fs_info, dest, logical, &read, i);
if (ret < 0 || read != len) {
continue;
}
finished = true;
break;
}
The problem being that read is always less than len.
I am not sure if __btrfs_map_block is changing "len" to the incorrect
value, or if there is some logic in "read_extent_data" that isn't
correct. Any pointers on how this code is supposed to work would be
greatly appreciated.
Thanks.
Thanks for reporting the issue
$ scripts/get_maintainer.pl -f fs/btrfs/volumes.c
suggests to include
"Marek Behún" <ka...@kernel.org> (maintainer:BTRFS)
Qu Wenruo <w...@suse.com> (reviewer:BTRFS)
linux-bt...@vger.kernel.org
to the communication.
Best regards
Heinrich
=== EXAMPLE 2 ===
Zynq> load mmc 1:0 0 16K
[btrfs_file_read,fs/btrfs/inode.c:710] === read the aligned part ===
[btrfs_read_extent_reg,fs/btrfs/inode.c:458] before read_extent_data
(ret = 0, read = 16384, len = 16384)
[read_extent_data,fs/btrfs/disk-io.c:547] before __btrfs_map_block
(len = 16384)
[read_extent_data,fs/btrfs/disk-io.c:550] after __btrfs_map_block (len
= 28672)
[read_extent_data,fs/btrfs/disk-io.c:565] before __btrfs_devread (len
= 16384)
[read_extent_data,fs/btrfs/disk-io.c:568] after __btrfs_devread (len =
16384)
[btrfs_read_extent_reg,fs/btrfs/inode.c:460] after read_extent_data
(ret = 0, read = 16384, len = 16384)
cur: 0, extent_num_bytes: 16384, aligned_end: 16384
16384 bytes read in 100 ms (159.2 KiB/s)
=== EXAMPLE 2 ===
Zynq> load mmc 1:0 0 32K
[btrfs_file_read,fs/btrfs/inode.c:710] === read the aligned part ===
[btrfs_read_extent_reg,fs/btrfs/inode.c:458] before read_extent_data
(ret = 0, read = 32768, len = 32768)
[read_extent_data,fs/btrfs/disk-io.c:547] before __btrfs_map_block
(len = 32768)
[read_extent_data,fs/btrfs/disk-io.c:550] after __btrfs_map_block (len
= 12288)
[read_extent_data,fs/btrfs/disk-io.c:565] before __btrfs_devread (len
= 12288)
[read_extent_data,fs/btrfs/disk-io.c:568] after __btrfs_devread (len =
12288)
So the first 3 sectors are before the stripe boundary and we read it
correctly.
[btrfs_read_extent_reg,fs/btrfs/inode.c:460] after read_extent_data
(ret = 0, read = 12288, len = 32768)
[btrfs_read_extent_reg,fs/btrfs/inode.c:458] before read_extent_data
(ret = 0, read = 12288, len = 32768)
[read_extent_data,fs/btrfs/disk-io.c:547] before __btrfs_map_block
(len = 12288)
[read_extent_data,fs/btrfs/disk-io.c:550] after __btrfs_map_block (len
= 12288)
I believe this is the problem.
If we're reading the full 32K, and the first 12K is in the first stripe,
we should then try to map the remaining 20K, not the 12K again.
I'll look into the situation.
But if you can provide the image or the dump, it can greatly help the
debugging.
Thanks,
Qu
[read_extent_data,fs/btrfs/disk-io.c:565] before __btrfs_devread (len
= 12288)
[read_extent_data,fs/btrfs/disk-io.c:568] after __btrfs_devread (len =
12288)
[btrfs_read_extent_reg,fs/btrfs/inode.c:460] after read_extent_data
(ret = 0, read = 12288, len = 32768)
file: fs/btrfs/inode.c, line: 468
cur: 0, extent_num_bytes: 32768, aligned_end: 32768
-----> btrfs_read_extent_reg: -5, line: 758
BTRFS: An error occurred while reading file 32K
Failed to load '32K'
Sam Winchenbach
Embedded Software Engineer III
Tethers Unlimited, Inc. | Connect Your Universe | www.tethers.com
swinchenb...@tethers.com | C: 207-974-6934
11711 North Creek Pkwy # D113, Bothell, WA 98011-8808, USA
