linux-ext4 - Re: [PATCH v3 05/10] ext4: restart handle if credits are insufficient during allocating blocks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <i7lzmvk5prgnw2zri46adshfjhfq63r7le5w5sv67wmkiimbhc@a24oub5o6xtg>
Date: Wed, 2 Jul 2025 16:18:21 +0200
From: Jan Kara <jack@...e.cz>
To: Zhang Yi <yi.zhang@...weicloud.com>
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, jack@...e.cz, 
	ojaswin@...ux.ibm.com, sashal@...nel.org, yi.zhang@...wei.com, libaokun1@...wei.com, 
	yukuai3@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH v3 05/10] ext4: restart handle if credits are
 insufficient during allocating blocks

On Tue 01-07-25 21:06:30, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
> 
> After large folios are supported on ext4, writing back a sufficiently
> large and discontinuous folio may consume a significant number of
> journal credits, placing considerable strain on the journal. For
> example, in a 20GB filesystem with 1K block size and 1MB journal size,
> writing back a 2MB folio could require thousands of credits in the
> worst-case scenario (when each block is discontinuous and distributed
> across different block groups), potentially exceeding the journal size.
> This issue can also occur in ext4_write_begin() and ext4_page_mkwrite()
> when delalloc is not enabled.
> 
> Fix this by ensuring that there are sufficient journal credits before
> allocating an extent in mpage_map_one_extent() and
> ext4_block_write_begin(). If there are not enough credits, return
> -EAGAIN, exit the current mapping loop, restart a new handle and a new
> transaction, and allocating blocks on this folio again in the next
> iteration.
> 
> Suggested-by: Jan Kara <jack@...e.cz>
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>

Very nice. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

One small comment below:

> +/*
> + * Make sure that the current journal transaction has enough credits to map
> + * one extent. Return -EAGAIN if it cannot extend the current running
> + * transaction.
> + */
> +static inline int ext4_journal_ensure_extent_credits(handle_t *handle,
> +						     struct inode *inode)
> +{
> +	int credits;
> +	int ret;
> +
> +	if (!handle)

Shouldn't this rather be ext4_handle_valid(handle) to catch nojournal mode
properly?

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR