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Date: Thu, 25 Jul 2019 04:54:42 -0700 From: Christoph Hellwig <hch@...radead.org> To: Damien Le Moal <damien.lemoal@....com> Cc: Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, Christoph Hellwig <hch@....de>, Johannes Thumshirn <jthumshirn@...e.de>, Naohiro Aota <naohiro.aota@....com>, Masato Suzuki <masato.suzuki@....com> Subject: Re: [PATCH] ext4: Fix deadlock on page reclaim On Thu, Jul 25, 2019 at 06:33:58PM +0900, Damien Le Moal wrote: > + gfp_t gfp_mask; > + > switch (ext4_inode_journal_mode(inode)) { > case EXT4_INODE_ORDERED_DATA_MODE: > case EXT4_INODE_WRITEBACK_DATA_MODE: > @@ -4019,6 +4019,14 @@ void ext4_set_aops(struct inode *inode) > inode->i_mapping->a_ops = &ext4_da_aops; > else > inode->i_mapping->a_ops = &ext4_aops; > + > + /* > + * Ensure all page cache allocations are done from GFP_NOFS context to > + * prevent direct reclaim recursion back into the filesystem and blowing > + * stacks or deadlocking. > + */ > + gfp_mask = mapping_gfp_mask(inode->i_mapping); > + mapping_set_gfp_mask(inode->i_mapping, (gfp_mask & ~(__GFP_FS))); This looks like something that could hit every file systems, so shouldn't we fix this in common code? We could also look into just using memalloc_nofs_save for the page cache allocation path instead of the per-mapping gfp_mask. > } > > static int __ext4_block_zero_page_range(handle_t *handle, > -- > 2.21.0 > ---end quoted text---
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