[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <F7AD868F-D88A-49BC-8E7C-0E2A7416695A@dilger.ca>
Date: Thu, 25 Jul 2019 13:57:36 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Christoph Hellwig <hch@...radead.org>
Cc: Damien Le Moal <damien.lemoal@....com>,
Theodore Ts'o <tytso@....edu>,
Ext4 Developers List <linux-ext4@...r.kernel.org>,
Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
linux-fsdevel <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 Jul 25, 2019, at 5:54 AM, Christoph Hellwig <hch@...radead.org> wrote:
>
> 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?
It also has the drawback that it prevents __GFP_FS reclaim when ext4
is *not* at the bottom of the IO stack.
> We could also look into just using memalloc_nofs_save for the page
> cache allocation path instead of the per-mapping gfp_mask.
That makes more sense.
Cheers, Andreas
Download attachment "signature.asc" of type "application/pgp-signature" (874 bytes)
Powered by blists - more mailing lists