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Date:   Sun, 8 May 2022 19:37:10 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Christoph Hellwig <hch@infradead.org>
Cc:     linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 32/69] buffer: Rewrite nobh_truncate_page() to use folios
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On Tue, May 03, 2022 at 07:41:24AM -0700, Christoph Hellwig wrote:
> The changes looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> But I wonder if we shouldn't really just drop these nobh helpers
> entirely.  They were added to save lowmem on highmem systems with a lot
> of highmem, but I really don't think we should continue optimizaing for
> that.

They certainly don't have a lot of users:

$ git grep -w nobh_truncate_page
fs/buffer.c:int nobh_truncate_page(struct address_space *mapping,
fs/buffer.c:EXPORT_SYMBOL(nobh_truncate_page);
fs/ext2/inode.c:                error = nobh_truncate_page(inode->i_mapping,
fs/jfs/inode.c: nobh_truncate_page(ip->i_mapping, ip->i_size, jfs_get_block);
include/linux/buffer_head.h:int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);

So just two for this helper.  The other nobh_ helpers are in a similar
position (just ext2 and jfs).  I had a quick look at converting jfs to
iomap, and that seems quite reasonable.  So ... once ext2 is converted
to iomap, all the nobh helpers can go away as being unused?