On Wed, Aug 27, 2008 at 7:24 PM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: > The direct I/O write codepath for CIFS is done through > cifs_user_write(). That function does not currently call > generic_write_checks() so the file position isn't being properly set > when the file is opened with O_APPEND. It's also not doing the other > "normal" checks that should be done for a write call. > > The problem is currently that when you open a file with O_APPEND on a > mount with the directio mount option, the file position is set to the > beginning of the file. This makes any subsequent writes clobber the data > in the file starting at the beginning. Is this important enough to go into stable after it goes to mainline (seems like a good candidate)? > This seems to fix the problem in cursory testing. It is, however > important to note that NFS disallows the combination of > (O_DIRECT|O_APPEND). If my understanding is correct, the concern is > races with multiple clients appending to a file clobbering each others' > data. Since the write model for CIFS and NFS is pretty similar in this > regard, At least for oplocked files (which NFSv3 does not have support for) we could allow append. (when appending on an O_DIRECT open or mount, also might be possible to open with DENY_WRITE mode rather than failing if races with other clients must be prevented but that could break apps). -- Thanks, Steve -- 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
