On Wed 26-08-09 22:27:00, Jamie Lokier wrote: > Jan Kara wrote: > > BH_Dirty > > - Ideally, this bit should mean "buffer has data that have to be > > written". But it is not quite true. The problem happens when > > someone calls set_page_dirty() on the page to which buffers are > > attached or similarly when buffers are attached to a dirty > > page. Then all buffers attached to the page are marked dirty - > > even those that are beyond end of file which obviously should not > > be written. > > > > When buffer is dirty, the page has to be dirty as well (mark > > buffer dirty takes care of that). It is not necessarily the other > > way around and buffer dirty bit is what ultimately decides whether > > the buffer goes to disk or not. > > That last sentence implies page can be dirty while a buffer in the > page is not dirty. Yes, that happens. > In that case, do buffers beyond the end of file need to be set dirty > by set_page_dirty()? If yes, perhaps the text could explain why. No, they need not. But it's racy to check i_size in set_page_dirty because we don't hold i_mutex... I'll add some explanation to the paragraph. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
