@@ -2706,11 +2706,15 @@ void folio_account_cleaned(struct folio *folio, struct bdi_writeback *wb)
* If warn is true, then emit a warning if the folio is not uptodate and has
* not been truncated.
*
- * The caller must hold folio_memcg_lock(). Most callers have the folio
- * locked. A few have the folio blocked from truncation through other
- * means (eg zap_vma_pages() has it mapped and is holding the page table
- * lock). This can also be called from mark_buffer_dirty(), which I
- * cannot prove is always protected against truncate.
+ * The caller must hold folio_memcg_lock(). It is the caller's
+ * responsibility to prevent the folio from being truncated while
+ * this function is in progress, although it may have been truncated
+ * before this function is called. Most callers have the folio locked.
+ * A few have the folio blocked from truncation through other means (e.g.
+ * zap_vma_pages() has it mapped and is holding the page table lock).
+ * When called from mark_buffer_dirty(), the filesystem should hold a
+ * reference to the buffer_head that is being marked dirty, which causes
+ * try_to_free_buffers() to fail.
*/
void __folio_mark_dirty(struct folio *folio, struct address_space *mapping,
int warn)
I've learned why it's safe to call __folio_mark_dirty() from mark_buffer_dirty() without holding the folio lock, so update the description to explain why. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> --- mm/page-writeback.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)