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Date: Thu, 19 Nov 2020 12:26:34 +0000 From: "Lyashkov, Alexey" <alexey.lyashkov@....com> To: "Theodore Y. Ts'o" <tytso@....edu>, Благодаренко Артём <artem.blagodarenko@...il.com> CC: "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>, "adilger.kernel@...ger.ca" <adilger.kernel@...ger.ca>, Theodore Tso <tytso@...gle.com> Subject: Re: [PATCH] libfs: Fix DIO mode aligment Tso, This situation hit with modern hdd with 4k block size and e2image changed to use DIRECT IO instead of buffered. e2fsprogs tries to read a super lock on offset 1k and it caused to set FS block size to 1k and second block reading. (many other places exist, but it simplest). >> if (superblock) { if (!block_size) { retval = EXT2_ET_INVALID_ARGUMENT; goto cleanup; } io_channel_set_blksize(fs->io, block_size); group_block = superblock; fs->orig_super = 0; } else { io_channel_set_blksize(fs->io, SUPERBLOCK_OFFSET); <<<<< this is problem superblock = 1; group_block = 0; retval = ext2fs_get_mem(SUPERBLOCK_SIZE, &fs->orig_super); if (retval) goto cleanup; } retval = io_channel_read_blk(fs->io, superblock, -SUPERBLOCK_SIZE, fs->super); >> It caused errors like # e2image -Q /dev/md65 /tmp/node05_image_out e2image 1.45.6.cr1 (14-Aug-2020) e2image: Attempt to read block from filesystem resulted in short read while trying to open /dev/md65 Couldn’t find valid filesystem superblock. It looks like I don't first person to found a bug, as someone was add Alex On 17/11/2020, 22:19, "Theodore Y. Ts'o" <tytso@....edu> wrote: On Tue, Nov 17, 2020 at 06:30:11PM +0300, Благодаренко Артём wrote: > Hello, > > Any thoughts about this change? Thanks. I'm trying to think of situations where this could actually trigger in real life. The only one I can think of is if a file system with a 1k block file system is located on an an Advanced FormatDrive with a 4k sector size. What was the use case where this was actually an issue? - Ted
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