Hi Jason, On 07/26/2017 01:45 PM, Jason Baron wrote: > Hi, > > In testing nowait aio on ext4, I found that when appending to a file > the return value is EAGAIN/EWOULDBLOCK, because as mentioned in the > commit this will potentially trigger an allocation. However, the EAGAIN, > seems somewhat misleading to me, in that if I continuously try the > write, it will never succeed. > > The relevant commit is: > 728fbc0 ext4: nowait aio support > > As you can see there, failure to get the inode lock is treated as > EAGAIN, which seems more appropriate to me, as its very likely > to succeed on subsequent calls. > > Perhaps, it could be switched to -EINVAL, or something else? > Thanks for testing this. I would suggest read it as -EWOULDBLOCK. The idea is to pass on IOCB_NOWAIT when we don't want the I/O process to wait, and if it does return -EWOULDBLOCK. If it returns EWOULDBLOCK in case of allocation, you may want to allocate your file space before performing the I/O. I would return EINVAL in case the parameters passed are incorrect. -- Goldwyn
