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
| ||
|
Message-ID: <f73b6973-3f7c-4e0e-9908-3a3f151715b5@huaweicloud.com> Date: Fri, 4 Jul 2025 09:40:23 +0800 From: Zhang Yi <yi.zhang@...weicloud.com> To: Jan Kara <jack@...e.cz> Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, 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 2025/7/4 0:27, Jan Kara wrote: > On Thu 03-07-25 10:13:07, Zhang Yi wrote: >> On 2025/7/2 22:18, Jan Kara wrote: >>> 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? >>> >> __ext4_journal_ensure_credits() already calls ext4_handle_valid() to handle >> nojournal mode, and the '!handle' check here is to handle the case where >> ext4_block_write_begin() passes in a NULL 'handle'. > > Ah, right. But then you don't need the test at all, do you? Anyway, > whatever you decide to do with this (or nothing) is fine by me. > Yeah, remove this test is fine with me. I added this one is because the comments in ext4_handle_valid() said "Do not use this for NULL handles." I think it is best to follow this rule. :) Best regards, Yi.
Powered by blists - more mailing lists