kernel/linux.git/include/linux/file.h, branch v6.12.80

Merge tag 'pull-stable-struct_fd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2024-09-23T16:35:36+00:00

Pull 'struct fd' updates from Al Viro: "Just the 'struct fd' layout change, with conversion to accessor helpers" * tag 'pull-stable-struct_fd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: add struct fd constructors, get rid of __to_fd() struct fd: representation change introduce fd_file(), convert all accessors to it.

Merge tag 'vfs-6.12.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2024-09-16T09:15:26+00:00

Pull vfs mount updates from Christian Brauner: "Recently, we added the ability to list mounts in other mount namespaces and the ability to retrieve namespace file descriptors without having to go through procfs by deriving them from pidfds. This extends nsfs in two ways: (1) Add the ability to retrieve information about a mount namespace via NS_MNT_GET_INFO. This will return the mount namespace id and the number of mounts currently in the mount namespace. The number of mounts can be used to size the buffer that needs to be used for listmount() and is in general useful without having to actually iterate through all the mounts. The structure is extensible. (2) Add the ability to iterate through all mount namespaces over which the caller holds privilege returning the file descriptor for the next or previous mount namespace. To retrieve a mount namespace the caller must be privileged wrt to it's owning user namespace. This means that PID 1 on the host can list all mounts in all mount namespaces or that a container can list all mounts of its nested containers. Optionally pass a structure for NS_MNT_GET_INFO with NS_MNT_GET_{PREV,NEXT} to retrieve information about the mount namespace in one go. (1) and (2) can be implemented for other namespace types easily. Together with recent api additions this means one can iterate through all mounts in all mount namespaces without ever touching procfs. The commit message in 49224a345c48 ('Merge patch series "nsfs: iterate through mount namespaces"') contains example code how to do this" * tag 'vfs-6.12.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: nsfs: iterate through mount namespaces file: add fput() cleanup helper fs: add put_mnt_ns() cleanup helper fs: allow mount namespace fd

add struct fd constructors, get rid of __to_fd()

2024-08-13T02:01:15+00:00

Make __fdget() et.al. return struct fd directly. New helpers: BORROWED_FD(file) and CLONED_FD(file), for borrowed and cloned file references resp. NOTE: this might need tuning; in particular, inline on __fget_light() is there to keep the code generation same as before - we probably want to keep it inlined in fdget() et.al. (especially so in fdget_pos()), but that needs profiling. Reviewed-by: Christian Brauner Signed-off-by: Al Viro

struct fd: representation change

2024-08-13T02:01:05+00:00

We want the compiler to see that fdput() on empty instance is a no-op. The emptiness check is that file reference is NULL, while fdput() is "fput() if FDPUT_FPUT is present in flags". The reason why fdput() on empty instance is a no-op is something compiler can't see - it's that we never generate instances with NULL file reference combined with non-zero flags. It's not that hard to deal with - the real primitives behind fdget() et.al. are returning an unsigned long value, unpacked by (inlined) __to_fd() into the current struct file * + int. The lower bits are used to store flags, while the rest encodes the pointer. Linus suggested that keeping this unsigned long around with the extractions done by inlined accessors should generate a sane code and that turns out to be the case. Namely, turning struct fd into a struct-wrapped unsinged long, with fd_empty(f) => unlikely(f.word == 0) fd_file(f) => (struct file *)(f.word & ~3) fdput(f) => if (f.word & 1) fput(fd_file(f)) ends up with compiler doing the right thing. The cost is the patch footprint, of course - we need to switch f.file to fd_file(f) all over the tree, and it's not doable with simple search and replace; there are false positives, etc. Note that the sole member of that structure is an opaque unsigned long - all accesses should be done via wrappers and I don't want to use a name that would invite manual casts to file pointers, etc. The value of that member is equal either to (unsigned long)p | flags, p being an address of some struct file instance, or to 0 for an empty fd. For now the new predicate (fd_empty(f)) has no users; all the existing checks have form (!fd_file(f)). We will convert to fd_empty() use later; here we only define it (and tell the compiler that it's unlikely to return true). This commit only deals with representation change; there will be followups. Reviewed-by: Christian Brauner Signed-off-by: Al Viro

introduce fd_file(), convert all accessors to it.

2024-08-13T02:00:43+00:00

For any changes of struct fd representation we need to turn existing accesses to fields into calls of wrappers. Accesses to struct fd::flags are very few (3 in linux/file.h, 1 in net/socket.c, 3 in fs/overlayfs/file.c and 3 more in explicit initializers). Those can be dealt with in the commit converting to new layout; accesses to struct fd::file are too many for that. This commit converts (almost) all of f.file to fd_file(f). It's not entirely mechanical ('file' is used as a member name more than just in struct fd) and it does not even attempt to distinguish the uses in pointer context from those in boolean context; the latter will be eventually turned into a separate helper (fd_empty()). NOTE: mass conversion to fd_empty(), tempting as it might be, is a bad idea; better do that piecewise in commit that convert from fdget...() to CLASS(...). [conflicts in fs/fhandle.c, kernel/bpf/syscall.c, mm/memcontrol.c caught by git; fs/stat.c one got caught by git grep] [fs/xattr.c conflict] Reviewed-by: Christian Brauner Signed-off-by: Al Viro

file: fix typo in take_fd() comment

2024-08-12T20:03:27+00:00

The explanatory comment above take_fd() contains a typo, fix that to not confuse readers. Signed-off-by: Mathias Krause Link: https://lore.kernel.org/r/20240809135035.748109-1-minipli@grsecurity.net Signed-off-by: Christian Brauner

file: add fput() cleanup helper

2024-08-09T10:44:50+00:00

Add a simple helper to put a file reference. Link: https://lore.kernel.org/r/20240719-work-mount-namespace-v1-4-834113cab0d2@kernel.org Reviewed-by: Josef Bacik Reviewed-by: Jeff Layton Signed-off-by: Christian Brauner

file: add take_fd() cleanup helper

2024-06-28T08:36:45+00:00

Add a helper that returns the file descriptor and ensures that the old variable contains a negative value. This makes it easy to rely on CLASS(get_unused_fd). Link: https://lore.kernel.org/r/20240627-work-pidfs-v1-1-7e9ab6cc3bb1@kernel.org Reviewed-by: Jeff Layton Reviewed-by: Josef Bacik Reviewed-by: Alexander Mikhalitsyn Signed-off-by: Christian Brauner

file: add fd_raw cleanup class

2024-05-09T11:02:39+00:00

So we can also use CLASS(fd_raw, f)(fd) for codepaths where we allow FMODE_PATH aka O_PATH file descriptors to be used. Signed-off-by: Christian Brauner

file: add alloc_file_pseudo_noaccount()

2024-02-25T11:05:08+00:00

When we open block devices as files we want to make sure to not charge them against the open file limit of the caller as that can cause spurious failures. Link: https://lore.kernel.org/r/20240123-vfs-bdev-file-v2-1-adbd023e19cc@kernel.org Signed-off-by: Christian Brauner