From: Aurelien DESBRIERES <aurelien@hackers.camp>
To: djwong@kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
viro@zeniv.linux.org.uk, brauner@kernel.org
Subject: Re: [RFC PATCH 01/10] ftrfs: add on-disk format and in-memory data structures
Date: Mon, 13 Apr 2026 19:26:55 +0200 [thread overview]
Message-ID: <1776101215.268662.47960.nullmailer@me> (raw)
In-Reply-To: <20260413151158.GW6202@frogsfrogsfrogs>
On Mon, Apr 13, 2026 at 05:11:XX PM +0200, Darrick J. Wong wrote:
> I don't see a block header for indirect blocks, so I guess this
> filesystem only supports mapping ($block_size / 4) ^ 2 +
> ($block_size / 4) + 12 blocks? IOWs, 1049612 of 4KiB blocks,
> or about 4GB of data? Why is isize 64-bit then?
Correct. With 4KiB blocks and 8-byte block pointers, the maximum
addressable file size is (512 + 512^2 + 12) * 4096 = ~1GB, not 4GB.
The 64-bit i_size is inconsistent with the block pointer scheme.
For the intended use case (MRAM/NOR flash on embedded space hardware),
files are small and a ~1GB limit is acceptable. i_size will be
corrected to __le32 in v2, or explicitly documented as capped at ~1GB
with a build-time assert.
Thank you for the precise calculation.
Aurelien DESBRIERES <aurelien@hackers.camp>
next prev parent reply other threads:[~2026-04-14 12:07 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-13 14:23 [RFC PATCH 0/10] ftrfs: Fault-Tolerant Radiation-Robust Filesystem Aurelien DESBRIERES
2026-04-13 14:23 ` [RFC PATCH 01/10] ftrfs: add on-disk format and in-memory data structures Aurelien DESBRIERES
2026-04-13 15:11 ` Darrick J. Wong
2026-04-13 17:26 ` Aurelien DESBRIERES [this message]
2026-04-13 14:23 ` [RFC PATCH 02/10] ftrfs: add superblock operations Aurelien DESBRIERES
2026-04-13 14:23 ` [RFC PATCH 03/10] ftrfs: add inode operations Aurelien DESBRIERES
2026-04-13 14:23 ` [RFC PATCH 04/10] ftrfs: add directory operations Aurelien DESBRIERES
2026-04-13 14:23 ` [RFC PATCH 05/10] ftrfs: add file operations Aurelien DESBRIERES
2026-04-13 15:09 ` Matthew Wilcox
[not found] ` <CAM=40tU5NppEZ9x07qDVkSxLw6Ga4nVg7sDCqcvhfQ51VbsS9Q@mail.gmail.com>
2026-04-13 17:41 ` Matthew Wilcox
2026-04-13 14:23 ` [RFC PATCH 06/10] ftrfs: add block and inode allocator Aurelien DESBRIERES
2026-04-13 15:21 ` Darrick J. Wong
2026-04-14 14:11 ` Aurelien DESBRIERES
2026-04-13 14:23 ` [RFC PATCH 07/10] ftrfs: add filename and directory entry operations Aurelien DESBRIERES
2026-04-13 14:23 ` [RFC PATCH 08/10] ftrfs: add CRC32 checksumming and Reed-Solomon FEC skeleton Aurelien DESBRIERES
2026-04-13 14:23 ` [RFC PATCH 09/10] ftrfs: add Kconfig, Makefile and fs/ tree integration Aurelien DESBRIERES
2026-04-13 14:23 ` [RFC PATCH 10/10] MAINTAINERS: add entry for FTRFS filesystem Aurelien DESBRIERES
2026-04-13 15:04 ` [RFC PATCH 0/10] ftrfs: Fault-Tolerant Radiation-Robust Filesystem Pedro Falcato
2026-04-13 18:03 ` Andreas Dilger
2026-04-14 2:56 ` Gao Xiang
2026-04-14 14:11 ` Aurelien DESBRIERES
2026-04-14 13:30 ` Aurelien DESBRIERES
2026-04-13 15:06 ` Matthew Wilcox
2026-04-13 18:11 ` Darrick J. Wong
2026-04-14 14:11 ` Aurelien DESBRIERES
2026-04-14 13:31 ` Aurelien DESBRIERES
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