On Mon, Feb 01, 2021 at 01:15:29PM -0300, Vinicius Tinti wrote: > On Mon, Feb 1, 2021 at 9:49 AM Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > > > > DX_DEBUG is completely dead code, so either kill it off or make it an > > actual CONFIG_* symbol through Kconfig if it seems useful. > > About the unreachable code in "if (0)" I think it could be removed. > It seems to be doing an extra check. > > About the DX_DEBUG I think I can do another patch adding it to Kconfig > as you and Nathan suggested. Yes, it's doing another check which is useful in terms of early detection of bugs when a developer has the code open for modifications. It slows down performance under normal circumstances, and assuming the code is bug-free(tm), it's entirely unnecessary --- which is why it's under an "if (0)". However, if there *is* a bug, having an early detection that the representation invariant of the data structure has been violated can be useful in root causing a bug. This would probably be clearer if the code was pulled out into a separate function with comments explaining that this is a rep invariant check. The main thing about DX_DEBUG right now is that it is **super** verbose. Unwary users who enable it.... will be sorry. If we want to make it to be a first-class feature enabled via CONFIG_EXT4_DEBUG, we should convert all of the dx_trace calls to use pr_debug so they are enabled only if dynamic debug enables those pr_debug() statements. And this should absolutely be a separate patch. Cheers, - Ted
