diff options
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/idmappings.rst | 14 | ||||
| -rw-r--r-- | Documentation/filesystems/locking.rst | 13 | ||||
| -rw-r--r-- | Documentation/filesystems/porting.rst | 25 | ||||
| -rw-r--r-- | Documentation/filesystems/tmpfs.rst | 85 | ||||
| -rw-r--r-- | Documentation/filesystems/vfs.rst | 12 |
5 files changed, 93 insertions, 56 deletions
diff --git a/Documentation/filesystems/idmappings.rst b/Documentation/filesystems/idmappings.rst index ad6d21640576..d095c5838f94 100644 --- a/Documentation/filesystems/idmappings.rst +++ b/Documentation/filesystems/idmappings.rst @@ -146,9 +146,10 @@ For the rest of this document we will prefix all userspace ids with ``u`` and all kernel ids with ``k``. Ranges of idmappings will be prefixed with ``r``. So an idmapping will be written as ``u0:k10000:r10000``. -For example, the id ``u1000`` is an id in the upper idmapset or "userspace -idmapset" starting with ``u1000``. And it is mapped to ``k11000`` which is a -kernel id in the lower idmapset or "kernel idmapset" starting with ``k10000``. +For example, within this idmapping, the id ``u1000`` is an id in the upper +idmapset or "userspace idmapset" starting with ``u0``. And it is mapped to +``k11000`` which is a kernel id in the lower idmapset or "kernel idmapset" +starting with ``k10000``. A kernel id is always created by an idmapping. Such idmappings are associated with user namespaces. Since we mainly care about how idmappings work we're not @@ -373,6 +374,13 @@ kernel maps the caller's userspace id down into a kernel id according to the caller's idmapping and then maps that kernel id up according to the filesystem's idmapping. +From the implementation point it's worth mentioning how idmappings are represented. +All idmappings are taken from the corresponding user namespace. + + - caller's idmapping (usually taken from ``current_user_ns()``) + - filesystem's idmapping (``sb->s_user_ns``) + - mount's idmapping (``mnt_idmap(vfsmnt)``) + Let's see some examples with caller/filesystem idmapping but without mount idmappings. This will exhibit some problems we can hit. After that we will revisit/reconsider these examples, this time using mount idmappings, to see how diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index ca3d24becbf5..b7e5a3841aa4 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 @@ -558,9 +560,8 @@ mutex or just to use i_size_read() instead. Note: this does not protect the file->f_pos against concurrent modifications since this is something the userspace has to take care about. -->iterate() is called with i_rwsem exclusive. - -->iterate_shared() is called with i_rwsem at least shared. +->iterate_shared() is called with i_rwsem held for reading, and with the +file f_pos_lock held exclusively ->fasync() is responsible for maintaining the FASYNC bit in filp->f_flags. Most instances call fasync_helper(), which does that maintenance, so it's diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst index d2d684ae7798..0f5da78ef4f9 100644 --- a/Documentation/filesystems/porting.rst +++ b/Documentation/filesystems/porting.rst @@ -537,7 +537,7 @@ vfs_readdir() is gone; switch to iterate_dir() instead **mandatory** -->readdir() is gone now; switch to ->iterate() +->readdir() is gone now; switch to ->iterate_shared() **mandatory** @@ -693,24 +693,19 @@ parallel now. --- -**recommended** +**mandatory** -->iterate_shared() is added; it's a parallel variant of ->iterate(). +->iterate_shared() is added. Exclusion on struct file level is still provided (as well as that between it and lseek on the same struct file), but if your directory has been opened several times, you can get these called in parallel. Exclusion between that method and all directory-modifying ones is still provided, of course. -Often enough ->iterate() can serve as ->iterate_shared() without any -changes - it is a read-only operation, after all. If you have any -per-inode or per-dentry in-core data structures modified by ->iterate(), -you might need something to serialize the access to them. If you -do dcache pre-seeding, you'll need to switch to d_alloc_parallel() for -that; look for in-tree examples. - -Old method is only used if the new one is absent; eventually it will -be removed. Switch while you still can; the old one won't stay. +If you have any per-inode or per-dentry in-core data structures modified +by ->iterate_shared(), you might need something to serialize the access +to them. If you do dcache pre-seeding, you'll need to switch to +d_alloc_parallel() for that; look for in-tree examples. --- @@ -930,9 +925,9 @@ should be done by looking at FMODE_LSEEK in file->f_mode. filldir_t (readdir callbacks) calling conventions have changed. Instead of returning 0 or -E... it returns bool now. false means "no more" (as -E... used to) and true - "keep going" (as 0 in old calling conventions). Rationale: -callers never looked at specific -E... values anyway. ->iterate() and -->iterate_shared() instance require no changes at all, all filldir_t ones in -the tree converted. +callers never looked at specific -E... values anyway. -> iterate_shared() +instances require no changes at all, all filldir_t ones in the tree +converted. --- diff --git a/Documentation/filesystems/tmpfs.rst b/Documentation/filesystems/tmpfs.rst index f18f46be5c0c..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. @@ -84,8 +84,6 @@ nr_inodes The maximum number of inodes for this instance. The default is half of the number of your physical RAM pages, or (on a machine with highmem) the number of lowmem RAM pages, whichever is the lower. -noswap Disables swap. Remounts must respect the original settings. - By default swap is enabled. ========= ============================================================ These parameters accept a suffix k, m or g for kilo, mega and giga and @@ -99,36 +97,65 @@ 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: + +====== =========================================================== +noswap Disables swap. Remounts must respect the original settings. + By default swap is enabled. +====== =========================================================== + tmpfs also supports Transparent Huge Pages which requires a kernel configured with CONFIG_TRANSPARENT_HUGEPAGE and with huge supported for your system (has_transparent_hugepage(), which is architecture specific). The mount options for this are: -====== ============================================================ -huge=0 never: disables huge pages for the mount -huge=1 always: enables huge pages for the mount -huge=2 within_size: only allocate huge pages if the page will be - fully within i_size, also respect fadvise()/madvise() hints. -huge=3 advise: only allocate huge pages if requested with - fadvise()/madvise() -====== ============================================================ - -There is a sysfs file which you can also use to control system wide THP -configuration for all tmpfs mounts, the file is: - -/sys/kernel/mm/transparent_hugepage/shmem_enabled - -This sysfs file is placed on top of THP sysfs directory and so is registered -by THP code. It is however only used to control all tmpfs mounts with one -single knob. Since it controls all tmpfs mounts it should only be used either -for emergency or testing purposes. The values you can set for shmem_enabled are: - -== ============================================================ --1 deny: disables huge on shm_mnt and all mounts, for - emergency use --2 force: enables huge on shm_mnt and all mounts, w/o needing - option, for testing -== ============================================================ +================ ============================================================== +huge=never Do not allocate huge pages. This is the default. +huge=always Attempt to allocate huge page every time a new page is needed. +huge=within_size Only allocate huge page if it will be fully within i_size. + Also respect madvise(2) hints. +huge=advise Only allocate huge page if requested with madvise(2). +================ ============================================================== + +See also Documentation/admin-guide/mm/transhuge.rst, which describes the +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 diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index cb2a97e49872..f8fe815ab1f3 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -260,9 +260,11 @@ filesystem. The following members are defined: void (*evict_inode) (struct inode *); void (*put_super) (struct super_block *); int (*sync_fs)(struct super_block *sb, int wait); - int (*freeze_super) (struct super_block *); + int (*freeze_super) (struct super_block *sb, + enum freeze_holder who); int (*freeze_fs) (struct super_block *); - int (*thaw_super) (struct super_block *); + int (*thaw_super) (struct super_block *sb, + enum freeze_wholder who); int (*unfreeze_fs) (struct super_block *); int (*statfs) (struct dentry *, struct kstatfs *); int (*remount_fs) (struct super_block *, int *, char *); @@ -515,6 +517,7 @@ 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 +678,10 @@ 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 ======================== |