diff options
author | Linus Torvalds | 2023-08-28 09:55:25 -0700 |
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committer | Linus Torvalds | 2023-08-28 09:55:25 -0700 |
commit | ecd7db20474c3859d4d01f34aaabf41bd28c7d84 (patch) | |
tree | 70d787f3138a907c3e6eb53c403beac3e2bf91c9 /Documentation/filesystems | |
parent | 615e95831ec3d428cc554ac12e9439e2d66038d3 (diff) | |
parent | 572a3d1e5d3a3e335b92e2c28a63c0b27944480c (diff) |
Merge tag 'v6.6-vfs.tmpfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull libfs and tmpfs updates from Christian Brauner:
"This cycle saw a lot of work for tmpfs that required changes to the
vfs layer. Andrew, Hugh, and I decided to take tmpfs through vfs this
cycle. Things will go back to mm next cycle.
Features
========
- By far the biggest work is the quota support for tmpfs. New tmpfs
quota infrastructure is added to support it and a new QFMT_SHMEM
uapi option is exposed.
This offers user and group quotas to tmpfs (project quotas will be
added later). Similar to other filesystems tmpfs quota are not
supported within user namespaces yet.
- Add support for user xattrs. While tmpfs already supports security
xattrs (security.*) and POSIX ACLs for a long time it lacked
support for user xattrs (user.*). With this pull request tmpfs will
be able to support a limited number of user xattrs.
This is accompanied by a fix (see below) to limit persistent simple
xattr allocations.
- Add support for stable directory offsets. Currently tmpfs relies on
the libfs provided cursor-based mechanism for readdir. This causes
issues when a tmpfs filesystem is exported via NFS.
NFS clients do not open directories. Instead, each server-side
readdir operation opens the directory, reads it, and then closes
it. Since the cursor state for that directory is associated with
the opened file it is discarded after each readdir operation. Such
directory offsets are not just cached by NFS clients but also
various userspace libraries based on these clients.
As it stands there is no way to invalidate the caches when
directory offsets have changed and the whole application depends on
unchanging directory offsets.
At LSFMM we discussed how to solve this problem and decided to
support stable directory offsets. libfs now allows filesystems like
tmpfs to use an xarrary to map a directory offset to a dentry. This
mechanism is currently only used by tmpfs but can be supported by
others as well.
Fixes
=====
- Change persistent simple xattrs allocations in libfs from
GFP_KERNEL to GPF_KERNEL_ACCOUNT so they're subject to memory
cgroup limits. Since this is a change to libfs it affects both
tmpfs and kernfs.
- Correctly verify {g,u}id mount options.
A new filesystem context is created via fsopen() which records the
namespace that becomes the owning namespace of the superblock when
fsconfig(FSCONFIG_CMD_CREATE) is called for filesystems that are
mountable in namespaces. However, fsconfig() calls can occur in a
namespace different from the namespace where fsopen() has been
called.
Currently, when fsconfig() is called to set {g,u}id mount options
the requested {g,u}id is mapped into a k{g,u}id according to the
namespace where fsconfig() was called from. The resulting k{g,u}id
is not guaranteed to be resolvable in the namespace of the
filesystem (the one that fsopen() was called in).
This means it's possible for an unprivileged user to create files
owned by any group in a tmpfs mount since it's possible to set the
setid bits on the tmpfs directory.
The contract for {g,u}id mount options and {g,u}id values in
general set from userspace has always been that they are translated
according to the caller's idmapping. In so far, tmpfs has been
doing the correct thing. But since tmpfs is mountable in
unprivileged contexts it is also necessary to verify that the
resulting {k,g}uid is representable in the namespace of the
superblock to avoid such bugs.
The new mount api's cross-namespace delegation abilities are
already widely used. Having talked to a bunch of userspace this is
the most faithful solution with minimal regression risks"
* tag 'v6.6-vfs.tmpfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
tmpfs,xattr: GFP_KERNEL_ACCOUNT for simple xattrs
mm: invalidation check mapping before folio_contains
tmpfs: trivial support for direct IO
tmpfs,xattr: enable limited user extended attributes
tmpfs: track free_ispace instead of free_inodes
xattr: simple_xattr_set() return old_xattr to be freed
tmpfs: verify {g,u}id mount options correctly
shmem: move spinlock into shmem_recalc_inode() to fix quota support
libfs: Remove parent dentry locking in offset_iterate_dir()
libfs: Add a lock class for the offset map's xa_lock
shmem: stable directory offsets
shmem: Refactor shmem_symlink()
libfs: Add directory operations for stable offsets
shmem: fix quota lock nesting in huge hole handling
shmem: Add default quota limit mount options
shmem: quota support
shmem: prepare shmem quota infrastructure
quota: Check presence of quota operation structures instead of ->quota_read and ->quota_write callbacks
shmem: make shmem_get_inode() return ERR_PTR instead of NULL
shmem: make shmem_inode_acct_block() return error
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r-- | Documentation/filesystems/locking.rst | 8 | ||||
-rw-r--r-- | Documentation/filesystems/tmpfs.rst | 38 | ||||
-rw-r--r-- | Documentation/filesystems/vfs.rst | 6 |
3 files changed, 46 insertions, 6 deletions
diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index 0ca479dbb1cd..6e833ed0b22e 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -85,13 +85,14 @@ prototypes:: struct dentry *dentry, struct fileattr *fa); int (*fileattr_get)(struct dentry *dentry, struct fileattr *fa); struct posix_acl * (*get_acl)(struct mnt_idmap *, struct dentry *, int); + struct offset_ctx *(*get_offset_ctx)(struct inode *inode); locking rules: all may block -============== ============================================= +============== ================================================== ops i_rwsem(inode) -============== ============================================= +============== ================================================== lookup: shared create: exclusive link: exclusive (both) @@ -115,7 +116,8 @@ atomic_open: shared (exclusive if O_CREAT is set in open flags) tmpfile: no fileattr_get: no or exclusive fileattr_set: exclusive -============== ============================================= +get_offset_ctx no +============== ================================================== Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_rwsem diff --git a/Documentation/filesystems/tmpfs.rst b/Documentation/filesystems/tmpfs.rst index 2cd8fa332feb..56a26c843dbe 100644 --- a/Documentation/filesystems/tmpfs.rst +++ b/Documentation/filesystems/tmpfs.rst @@ -21,8 +21,8 @@ explained further below, some of which can be reconfigured dynamically on the fly using a remount ('mount -o remount ...') of the filesystem. A tmpfs filesystem can be resized but it cannot be resized to a size below its current usage. tmpfs also supports POSIX ACLs, and extended attributes for the -trusted.* and security.* namespaces. ramfs does not use swap and you cannot -modify any parameter for a ramfs filesystem. The size limit of a ramfs +trusted.*, security.* and user.* namespaces. ramfs does not use swap and you +cannot modify any parameter for a ramfs filesystem. The size limit of a ramfs filesystem is how much memory you have available, and so care must be taken if used so to not run out of memory. @@ -97,6 +97,9 @@ mount with such options, since it allows any user with write access to use up all the memory on the machine; but enhances the scalability of that instance in a system with many CPUs making intensive use of it. +If nr_inodes is not 0, that limited space for inodes is also used up by +extended attributes: "df -i"'s IUsed and IUse% increase, IFree decreases. + tmpfs blocks may be swapped out, when there is a shortage of memory. tmpfs has a mount option to disable its use of swap: @@ -123,6 +126,37 @@ sysfs file /sys/kernel/mm/transparent_hugepage/shmem_enabled: which can be used to deny huge pages on all tmpfs mounts in an emergency, or to force huge pages on all tmpfs mounts for testing. +tmpfs also supports quota with the following mount options + +======================== ================================================= +quota User and group quota accounting and enforcement + is enabled on the mount. Tmpfs is using hidden + system quota files that are initialized on mount. +usrquota User quota accounting and enforcement is enabled + on the mount. +grpquota Group quota accounting and enforcement is enabled + on the mount. +usrquota_block_hardlimit Set global user quota block hard limit. +usrquota_inode_hardlimit Set global user quota inode hard limit. +grpquota_block_hardlimit Set global group quota block hard limit. +grpquota_inode_hardlimit Set global group quota inode hard limit. +======================== ================================================= + +None of the quota related mount options can be set or changed on remount. + +Quota limit parameters accept a suffix k, m or g for kilo, mega and giga +and can't be changed on remount. Default global quota limits are taking +effect for any and all user/group/project except root the first time the +quota entry for user/group/project id is being accessed - typically the +first time an inode with a particular id ownership is being created after +the mount. In other words, instead of the limits being initialized to zero, +they are initialized with the particular value provided with these mount +options. The limits can be changed for any user/group id at any time as they +normally can be. + +Note that tmpfs quotas do not support user namespaces so no uid/gid +translation is done if quotas are enabled inside user namespaces. + tmpfs has a mount option to set the NUMA memory allocation policy for all files in that instance (if CONFIG_NUMA is enabled) - which can be adjusted on the fly via 'mount -o remount ...' diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index cb2a97e49872..898d0b43109e 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -515,6 +515,7 @@ As of kernel 2.6.22, the following members are defined: int (*fileattr_set)(struct mnt_idmap *idmap, struct dentry *dentry, struct fileattr *fa); int (*fileattr_get)(struct dentry *dentry, struct fileattr *fa); + struct offset_ctx *(*get_offset_ctx)(struct inode *inode); }; Again, all methods are called without any locks being held, unless @@ -675,7 +676,10 @@ otherwise noted. called on ioctl(FS_IOC_SETFLAGS) and ioctl(FS_IOC_FSSETXATTR) to change miscellaneous file flags and attributes. Callers hold i_rwsem exclusive. If unset, then fall back to f_op->ioctl(). - +``get_offset_ctx`` + called to get the offset context for a directory inode. A + filesystem must define this operation to use + simple_offset_dir_operations. The Address Space Object ======================== |