| Message ID | 20241115-vfs-tmpfs-d443d413eb26@brauner (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [GIT,PULL] vfs tmpfs | expand |
On Fri, 15 Nov 2024 at 06:07, Christian Brauner <brauner@kernel.org> wrote: > > This adds case-insensitive support for tmpfs. Ugh. I've pulled this, but I don't love it. This pattern: if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir)) d_add(dentry, inode); else d_instantiate(dentry, inode); needs an explanation, and probably a helper. And > include/linux/shmem_fs.h | 6 +- > mm/shmem.c | 265 ++++++++++++++++++++++++++++++++++-- I'm starting to think this should be renamed and/or possibly split up a bit. The actual path component handling functions should be moved out of mm/shmem.c. The whole "mm/shmem.c" thing made sense back in the days when this was mainly about memory management functions with some thing wrappers for exposing them as a filesystem, and tmpfs was kind of an odd special case. Those thin wrappers aren't very thin any more, and "shmem" is becoming something of a misnomer with the actual filesystem being called "tmpfs". We also actually have *two* different implementations of "tmpfs" - both in that same file - which is really annoying. The other one is based on the ramfs code. Would it be possible to try to make this a bit saner? Linus
The pull request you sent on Fri, 15 Nov 2024 15:06:58 +0100:
> git@gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs tags/vfs-6.13.tmpfs
has been merged into torvalds/linux.git:
https://git.kernel.org/torvalds/c/7956186e751bc15541ede638008feedc0e427883
Thank you!
On Mon, Nov 18, 2024 at 11:26:12AM -0800, Linus Torvalds wrote: > On Fri, 15 Nov 2024 at 06:07, Christian Brauner <brauner@kernel.org> wrote: > > > > This adds case-insensitive support for tmpfs. > > Ugh. > > I've pulled this, but I don't love it. > > This pattern: > > if (IS_ENABLED(CONFIG_UNICODE) && IS_CASEFOLDED(dir)) > d_add(dentry, inode); > else > d_instantiate(dentry, inode); > > needs an explanation, and probably a helper. I think we had this discussion before where we decided to move all the checks inline. But yes, this could probably be refactored to be easier to understand. > > And > > > include/linux/shmem_fs.h | 6 +- > > mm/shmem.c | 265 ++++++++++++++++++++++++++++++++++-- > > I'm starting to think this should be renamed and/or possibly split up > a bit. The actual path component handling functions should be moved > out of mm/shmem.c. > > The whole "mm/shmem.c" thing made sense back in the days when this was > mainly about memory management functions with some thing wrappers for > exposing them as a filesystem, and tmpfs was kind of an odd special > case. > > Those thin wrappers aren't very thin any more, and "shmem" is becoming > something of a misnomer with the actual filesystem being called > "tmpfs". > > We also actually have *two* different implementations of "tmpfs" - > both in that same file - which is really annoying. The other one is > based on the ramfs code. > > Would it be possible to try to make this a bit saner? So one possibility would be to move tmpfs into fs and have fs/tmpfs/ (or mm/tmpfs/) which would also be nice because mm/shmem.c is actively confusing when you're looking for the tmpfs code. And then it could simply be split up. I'm all for it.
diff --cc include/linux/fs.h index 3e53ba079f17,001d580af862..eae7ce884030 --- a/include/linux/fs.h
Hey Linus, /* Summary */ This adds case-insensitive support for tmpfs. The work contained in here adds support for case-insensitive file names lookups in tmpfs. The main difference from other casefold filesystems is that tmpfs has no information on disk, just on RAM, so we can't use mkfs to create a case-insensitive tmpfs. For this implementation, there's a mount option for casefolding. The rest of the patchset follows a similar approach as ext4 and f2fs. The use case for this feature is similar to the use case for ext4, to better support compatibility layers (like Wine), particularly in combination with sandboxing/container tools (like Flatpak). Those containerization tools can share a subset of the host filesystem with an application. In the container, the root directory and any parent directories required for a shared directory are on tmpfs, with the shared directories bind-mounted into the container's view of the filesystem. If the host filesystem is using case-insensitive directories, then the application can do lookups inside those directories in a case-insensitive way, without this needing to be implemented in user-space. However, if the host is only sharing a subset of a case-insensitive directory with the application, then the parent directories of the mount point will be part of the container's root tmpfs. When the application tries to do case-insensitive lookups of those parent directories on a case-sensitive tmpfs, the lookup will fail. /* Testing */ gcc version 14.2.0 (Debian 14.2.0-6) Debian clang version 16.0.6 (27+b1) All patches are based on v6.12-rc4 and have been sitting in linux-next. No build failures or warnings were observed. /* Conflicts */ Merge conflicts with mainline ============================= No known conflicts. Merge conflicts with other trees ================================ No known conflicts. This will have a minor merge conflict with the vfs-6.13.file pull request I sent as: https://lore.kernel.org/r/20241115-vfs-file-f2297d7c58ee@brauner The resolution for the conflict should look like this: +++ b/include/linux/fs.h @@@ -45,7 -45,7 +45,8 @@@ #include <linux/slab.h> #include <linux/maple_tree.h> #include <linux/rw_hint.h> +#include <linux/file_ref.h> + #include <linux/unicode.h> The following changes since commit 42f7652d3eb527d03665b09edac47f85fb600924: Linux 6.12-rc4 (2024-10-20 15:19:38 -0700) are available in the Git repository at: git@gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs tags/vfs-6.13.tmpfs for you to fetch changes up to 552b15103db404c7971d4958e6e28d4e7123a325: Merge patch series "tmpfs: Casefold fixes" (2024-11-06 11:22:30 +0100) Please consider pulling these changes from the signed vfs-6.13.tmpfs tag. Thanks! Christian ---------------------------------------------------------------- vfs-6.13.tmpfs ---------------------------------------------------------------- André Almeida (12): libfs: Create the helper function generic_ci_validate_strict_name() ext4: Use generic_ci_validate_strict_name helper unicode: Export latest available UTF-8 version number unicode: Recreate utf8_parse_version() libfs: Export generic_ci_ dentry functions tmpfs: Add casefold lookup support tmpfs: Add flag FS_CASEFOLD_FL support for tmpfs dirs tmpfs: Expose filesystem features via sysfs docs: tmpfs: Add casefold options libfs: Fix kernel-doc warning in generic_ci_validate_strict_name tmpfs: Fix type for sysfs' casefold attribute tmpfs: Initialize sysfs during tmpfs init Christian Brauner (2): Merge patch series "tmpfs: Add case-insensitive support for tmpfs" Merge patch series "tmpfs: Casefold fixes" Documentation/filesystems/tmpfs.rst | 24 ++++ fs/ext4/namei.c | 5 +- fs/libfs.c | 12 +- fs/unicode/utf8-core.c | 26 ++++ fs/unicode/utf8-selftest.c | 3 - include/linux/fs.h | 49 +++++++ include/linux/shmem_fs.h | 6 +- include/linux/unicode.h | 4 + mm/shmem.c | 265 ++++++++++++++++++++++++++++++++++-- 9 files changed, 371 insertions(+), 23 deletions(-)