Am 29.12.2010 20:04, schrieb Guillem Jover: > Hi! > > On Wed, 2010-12-29 at 17:58:41 +0100, Raphael Hertzog wrote: >> On Wed, 29 Dec 2010, Julien Cristau wrote: >> >>> You're ignoring the return value of sync_file_range (and posix_fadvise). >>> While that may be ok for SYNC_FILE_RANGE_WRITE, I don't think it is for >>> SYNC_FILE_RANGE_WAIT_BEFORE. >> >> It is ok since fsync() is still called afterwards. Both are only useful >> to avoid the speed-penalty that fsync() was giving us, but fsync() is >> still executed (and is usualy a no-op since the work has already been done >> thanks to the sync_file_range calls). > > Exactly, and although SYNC_FILE_RANGE_WAIT_BEFORE can return with EIO > or ENOSPC, if that would happen the pages would not have been flushed > and would still be dirty, and fsync() would go over them again. > [...] > > This was done on purpose, as those actions should be considered > equivalent to asynchronous hints for the kernel from dpkg's code PoV.
Forgive me if this was already done, but should this be documented in the code? I mean something like "We are ignoring the return value of SYNC_FILE_RANGE_WAIT_BEFORE on purpose since we call fsync() later on anyhow." near the SYNC_FILE... call and a "don't remove the fsync call unless you check the SYNC_FILE_.... system call return values" near the fsync call. In other words: Add comments why you do it the way you do it. Don't bother with comments that explain what you do. ;-) regards, Sv<just stumbled over this discussion>en -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected] Archive: http://lists.debian.org/[email protected]
