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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
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