Hi, On Fri 25-04-08 16:38:23, Mingming Cao wrote: > While looking at a bug related to direct IO returns to EIO, after > looking at the code, I found there is a window that > try_to_free_buffers() from direct IO could race with JBD, which holds > the reference to the data buffers before journal_commit_transaction() > ensures the data buffers has reached to the disk. > > A little more detail: to prepare for direct IO, generic_file_direct_IO() > calls invalidate_inode_pages2_range() to invalidate the pages in the > cache before performaning direct IO. invalidate_inode_pages2_range() > tries to free the buffers via try_to free_buffers(), but sometimes it > can't, due to the buffers is possible still on some transaction's > t_sync_datalist or t_locked_list waiting for > journal_commit_transaction() to process it. > > Currently Direct IO simply returns EIO if try_to_free_buffers() finds > the buffer is busy, as it has no clue that JBD is referencing it. > > Is this a known issue and expected behavior? Any thoughts? Are you seeing this in data=ordered mode? As Andrew pointed out we do filemap_write_and_wait() so all the relevant data buffers of the inode should be already on disk. In __journal_try_to_free_buffer() we check whether the buffer is already-written-out data buffer and unfile and free it in that case. It shouldn't happen that a data buffer has b_next_transaction set so really the only idea why try_to_free_buffers() could fail is that somebody manages to write to a page via mmap before invalidate_inode_pages2_range() gets to it. Under which kind of load do you observe the problem? Do you know exactly because of which condition does journal_try_to_free_buffers() fail? Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
