On Mon, Jun 22, 2020 at 06:50:17PM -0700, Eric Biggers wrote: > On Tue, Jun 23, 2020 at 10:46:36AM +1000, Dave Chinner wrote: > > On Wed, Jun 17, 2020 at 08:19:35PM -0700, Eric Biggers wrote: > > > Are you objecting to the use of a SB_* flag, or just to showing the flag > > > in > > > show_sb_opts() instead of in the individual filesystems? Note that the > > > SB_* > > > flag was requested by Christoph > > > (https://lkml.kernel.org/r/20191031183217.gf23...@infradead.org/, > > > https://lkml.kernel.org/r/20191031212103.ga6...@infradead.org/). We > > > originally > > > used a function fscrypt_operations::inline_crypt_enabled() instead. > > > > I'm objecting to the layering violations of having the filesystem > > control the mount option parsing and superblock feature flags, but > > then having no control over whether features that the filesystem has > > indicated to the VFS it is using get emitted as a mount option or > > not, and then having the VFS code unconditionally override the > > functionality that the filesystem uses because it thinks it's a > > mount option the filesystem supports.... > > > > For example, the current mess that has just come to light: > > filesystems like btrfs and XFS v5 which set SB_IVERSION > > unconditionally (i.e. it's not a mount option!) end up having that > > functionality turned off on remount because the VFS conflates > > MS_IVERSION with SB_IVERSION and so unconditionally clears > > SB_IVERSION because MS_IVERSION is not set on remount by userspace. > > Which userspace will never set be because the filesystems don't put > > "iversion" in their mount option strings because -its not a mount > > option- for those filesystems. > > > > See the problem? MS_IVERSION should be passed to the filesystem to > > deal with as a mount option, not treated as a flag to directly > > change SB_IVERSION in the superblock. > > > > We really need to stop with the "global mount options for everyone > > at the VFS" and instead pass everything down to the filesystems to > > parse appropriately. Yes, provide generic helper functions to deal > > with the common flags that everything supports, but the filesystems > > should be masking off mount options they doesn't support changing > > before changing their superblock feature support mask.... > > I think the MS_* flags are best saved for mount options that are applicable to > many/most filesystems and are mostly/entirely implementable at the VFS level.
That's the theory, but so far it's caused nothing but pain. In reality, I think ithe only sane way forward if to stop mount option parsing in userspace (i.e. no new MS_* flags) for any new functionality as it only leads to future pain. i.e. all new mount options should be parsed entirely in the kernel by the filesystem parsing code.... > I don't think "inlinecrypt" qualifies, since while it will be shared by the > block device-based filesystems that support fscrypt, that is only 2 > filesystems > currently; and while some of the code needed to implement it is shared in > fs/crypto/, there are still substantial filesystem-specific hooks needed. Right. I wasn't suggesting this patchset should use an MS_ flag - it was pointing out the problem with the VFS code using SB_ flags to indicate enabled filesystem functionality unconditionally as a mount option that can be changed by userspace. > Hence this patchset intentionally does *not* allocate an MS_INLINECRYPT flag. > > I believe that already addresses half of your concern, as it means > SB_INLINECRYPT can only be set/cleared by the filesystem itself, not by the > VFS. > (But the commit message could use an explanation of this.) > > The other half would be addressed by the following change, right? Yes, it does. Thanks, Eric! Cheers, Dave. -- Dave Chinner da...@fromorbit.com _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
