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From: Hillf Danton <hdanton@sina.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Genes Lists <lists@sapience.com>,
	linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: 6.6.8 stable: crash in folio_mark_dirty
Date: Wed,  3 Jan 2024 18:49:07 +0800
Message-Id: <20240103104907.2657-1-hdanton@sina.com>
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References: <8bb29431064fc1f70a42edef75a8788dd4a0eecc.camel@sapience.com> <20231231012846.2355-1-hdanton@sina.com> <20240101015504.2446-1-hdanton@sina.com> <20240101113316.2595-1-hdanton@sina.com>
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On Mon, 1 Jan 2024 14:11:02 +0000 Matthew Wilcox
> 
> From an mm point of view, what is implicit is that truncate calls
> unmap_mapping_folio -> unmap_mapping_range_tree ->
> unmap_mapping_range_vma -> zap_page_range_single -> unmap_single_vma ->
> unmap_page_range -> zap_p4d_range -> zap_pud_range -> zap_pmd_range ->
> zap_pte_range -> pte_offset_map_lock()
> 
> So a truncate will take the page lock, then spin on the pte lock
> until the racing munmap() has finished (ok, this was an exit(), not
> a munmap(), but exit() does an implicit munmap()).
> 
But ptl fails to explain the warning reported, while the sequence in
__block_commit_write()

	mark_buffer_dirty();
	folio_mark_uptodate();

hints the warning is bogus.