On Fri, 25 Apr 2008 16:38:23 -0700 Mingming Cao <cmm@xxxxxxxxxx> wrote: > Hi, > > 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? Something like that might be possible, although people used to test buffered-vs-direct fairly heavily. generic_file_direct_IO() will run filemap_write_and_wait()->filemap_fdatawrite() under i_mutex, and this should run commits, write back dirty pages, etc. There might remain races though, perhaps with page faults. -- 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
