![]() | |||||||||||||
Messages in this thread |
On Sun, Jan 04, 2004 at 09:06:42PM -0800, Andrew Morton wrote: > Suparna Bhattacharya <suparna@in.ibm.com> wrote: > > > > > What is the significance of `written > count' in there, and of `dio->result > > > > dio->size' in finished_one_bio()? How can these states come about? > > > > > > > Both of these are checks to determine whether all or only a part of > > the request was serviced by DIO, leaving the rest to be serviced by > > falling back to buffered I/O. > > > > Earlier, we would decide this based on whether dio->result == -ENOTBLK > > and written == -ENOTBLK respectively. However, now that we also need the > > result to indicate how much actually got written even in -ENOTBLK case, > > so that we can issue buffered i/o only for the remaining part of the request, > > dio->result and written had to be modified to reflect the number of bytes > > transferred by DIO even for the fallback to buffered i/o case. > > So we need checks like this to find out whether there is some i/o left > > to be issued via buffered i/o. > > Sure. But the generic_file_aio_write_nolock() code is doing this: > > if (written >= count && !is_sync_kiocb(iocb)) > written = -EIOCBQUEUED; > if (written < 0 || written >= count) > goto out_status; > > > Under what circumstances can `written' (the amount which was written) be > greater than `count' (the amount to write)? None. The '>' situation should never occur. This is just being explicit about covering the "not less than" case as a whole, and making sure we do not fall through to buffered i/o in that case, i.e its the same as: if (!(written < count) && !is_sync_kiocb(iocb)) Is that any less confusing ? Or would you rather just replace the '>=" by "=='. Regards Suparna -- Suparna Bhattacharya (suparna@in.ibm.com) Linux Technology Center IBM Software Lab, India - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
| Last update: 2005-03-22 12:59 [from the cache] ©2003-2008 | |||||||||||||