The previous comment was not terribly helpful. Be a bit more explicit about the necessary locking environment. Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> --- mm/page-writeback.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 7e2da284e427..fa1117db4610 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -2602,10 +2602,12 @@ EXPORT_SYMBOL(folio_redirty_for_writepage); * folio_mark_dirty - Mark a folio as being modified. * @folio: The folio. * - * For folios with a mapping this should be done with the folio lock held - * for the benefit of asynchronous memory errors who prefer a consistent - * dirty state. This rule can be broken in some special cases, - * but should be better not to. + * The folio may not be truncated while this function is running. + * Holding the folio lock is sufficient to prevent truncation, but some + * callers cannot acquire a sleeping lock. These callers instead hold + * the page table lock for a page table which contains at least one page + * in this folio. Truncation will block on the page table lock as it + * unmaps pages before removing the folio from its mapping. * * Return: True if the folio was newly dirtied, false if it was already dirty. */ -- 2.34.1
