On 2024/8/14 13:32, Christoph Hellwig wrote: > On Mon, Aug 12, 2024 at 08:11:56PM +0800, Zhang Yi wrote: >> From: Zhang Yi <yi.zhang@xxxxxxxxxx> >> >> Now we allocate ifs if i_blocks_per_folio is larger than one when >> writing back dirty folios in iomap_writepage_map(), so we don't attach >> an ifs after buffer write to an entire folio until it starts writing >> back, if we partial truncate that folio, iomap_invalidate_folio() can't >> clear counterpart block's dirty bit as expected. Fix this by advance the >> ifs allocation to __iomap_write_begin(). > > Wouldn't it make more sense to only allocate the ifѕ in > iomap_invalidate_folio when it actually is needed? > I forget to mention that truncate_inode_partial_folio() call folio_invalidate()->iomap_invalidate_folio() only when the folio has private, if the folio doesn't has ifs, the iomap_invalidate_folio() would nerver be called, hence allocate the ifs in iomap_invalidate_folio() is useless. In my opinion, one solution is change to always call folio_invalidate() in truncate_inode_partial_folio(), all callbacks should handle the no private case. Another solution is add a magic (a fake ifs) to folio->private and then convert it to a real one in iomap_invalidate_folio(), any thoughts? Thanks, Yi.
