linux-kernel - Re: 6.6.8 stable: crash in folio_mark

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Date: Wed,  3 Jan 2024 18:49:07 +0800
From: Hillf Danton <hdanton@...a.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Genes Lists <lists@...ience.com>,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: 6.6.8 stable: crash in folio_mark_dirty

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.