aboutsummaryrefslogtreecommitdiff
path: root/Documentation/filesystems
diff options
context:
space:
mode:
authorLinus Torvalds2023-08-28 09:55:25 -0700
committerLinus Torvalds2023-08-28 09:55:25 -0700
commitecd7db20474c3859d4d01f34aaabf41bd28c7d84 (patch)
tree70d787f3138a907c3e6eb53c403beac3e2bf91c9 /Documentation/filesystems
parent615e95831ec3d428cc554ac12e9439e2d66038d3 (diff)
parent572a3d1e5d3a3e335b92e2c28a63c0b27944480c (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.rst8
-rw-r--r--Documentation/filesystems/tmpfs.rst38
-rw-r--r--Documentation/filesystems/vfs.rst6
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
========================