diff options
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/caching/cachefiles.rst | 178 | ||||
| -rw-r--r-- | Documentation/filesystems/caching/netfs-api.rst | 4 | ||||
| -rw-r--r-- | Documentation/filesystems/fscrypt.rst | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/fsverity.rst | 37 | ||||
| -rw-r--r-- | Documentation/filesystems/idmappings.rst | 5 | ||||
| -rw-r--r-- | Documentation/filesystems/locking.rst | 58 | ||||
| -rw-r--r-- | Documentation/filesystems/netfs_library.rst | 9 | ||||
| -rw-r--r-- | Documentation/filesystems/porting.rst | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/proc.rst | 246 | ||||
| -rw-r--r-- | Documentation/filesystems/vfs.rst | 103 | ||||
| -rw-r--r-- | Documentation/filesystems/zonefs.rst | 52 |
11 files changed, 457 insertions, 239 deletions
diff --git a/Documentation/filesystems/caching/cachefiles.rst b/Documentation/filesystems/caching/cachefiles.rst index 8bf396b76359..fc7abf712315 100644 --- a/Documentation/filesystems/caching/cachefiles.rst +++ b/Documentation/filesystems/caching/cachefiles.rst @@ -28,6 +28,7 @@ Cache on Already Mounted Filesystem (*) Debugging. + (*) On-demand Read. Overview @@ -482,3 +483,180 @@ the control file. For example:: echo $((1|4|8)) >/sys/module/cachefiles/parameters/debug will turn on all function entry debugging. + + +On-demand Read +============== + +When working in its original mode, CacheFiles serves as a local cache for a +remote networking fs - while in on-demand read mode, CacheFiles can boost the +scenario where on-demand read semantics are needed, e.g. container image +distribution. + +The essential difference between these two modes is seen when a cache miss +occurs: In the original mode, the netfs will fetch the data from the remote +server and then write it to the cache file; in on-demand read mode, fetching +the data and writing it into the cache is delegated to a user daemon. + +``CONFIG_CACHEFILES_ONDEMAND`` should be enabled to support on-demand read mode. + + +Protocol Communication +---------------------- + +The on-demand read mode uses a simple protocol for communication between kernel +and user daemon. The protocol can be modeled as:: + + kernel --[request]--> user daemon --[reply]--> kernel + +CacheFiles will send requests to the user daemon when needed. The user daemon +should poll the devnode ('/dev/cachefiles') to check if there's a pending +request to be processed. A POLLIN event will be returned when there's a pending +request. + +The user daemon then reads the devnode to fetch a request to process. It should +be noted that each read only gets one request. When it has finished processing +the request, the user daemon should write the reply to the devnode. + +Each request starts with a message header of the form:: + + struct cachefiles_msg { + __u32 msg_id; + __u32 opcode; + __u32 len; + __u32 object_id; + __u8 data[]; + }; + +where: + + * ``msg_id`` is a unique ID identifying this request among all pending + requests. + + * ``opcode`` indicates the type of this request. + + * ``object_id`` is a unique ID identifying the cache file operated on. + + * ``data`` indicates the payload of this request. + + * ``len`` indicates the whole length of this request, including the + header and following type-specific payload. + + +Turning on On-demand Mode +------------------------- + +An optional parameter becomes available to the "bind" command:: + + bind [ondemand] + +When the "bind" command is given no argument, it defaults to the original mode. +When it is given the "ondemand" argument, i.e. "bind ondemand", on-demand read +mode will be enabled. + + +The OPEN Request +---------------- + +When the netfs opens a cache file for the first time, a request with the +CACHEFILES_OP_OPEN opcode, a.k.a an OPEN request will be sent to the user +daemon. The payload format is of the form:: + + struct cachefiles_open { + __u32 volume_key_size; + __u32 cookie_key_size; + __u32 fd; + __u32 flags; + __u8 data[]; + }; + +where: + + * ``data`` contains the volume_key followed directly by the cookie_key. + The volume key is a NUL-terminated string; the cookie key is binary + data. + + * ``volume_key_size`` indicates the size of the volume key in bytes. + + * ``cookie_key_size`` indicates the size of the cookie key in bytes. + + * ``fd`` indicates an anonymous fd referring to the cache file, through + which the user daemon can perform write/llseek file operations on the + cache file. + + +The user daemon can use the given (volume_key, cookie_key) pair to distinguish +the requested cache file. With the given anonymous fd, the user daemon can +fetch the data and write it to the cache file in the background, even when +kernel has not triggered a cache miss yet. + +Be noted that each cache file has a unique object_id, while it may have multiple +anonymous fds. The user daemon may duplicate anonymous fds from the initial +anonymous fd indicated by the @fd field through dup(). Thus each object_id can +be mapped to multiple anonymous fds, while the usr daemon itself needs to +maintain the mapping. + +When implementing a user daemon, please be careful of RLIMIT_NOFILE, +``/proc/sys/fs/nr_open`` and ``/proc/sys/fs/file-max``. Typically these needn't +be huge since they're related to the number of open device blobs rather than +open files of each individual filesystem. + +The user daemon should reply the OPEN request by issuing a "copen" (complete +open) command on the devnode:: + + copen <msg_id>,<cache_size> + +where: + + * ``msg_id`` must match the msg_id field of the OPEN request. + + * When >= 0, ``cache_size`` indicates the size of the cache file; + when < 0, ``cache_size`` indicates any error code encountered by the + user daemon. + + +The CLOSE Request +----------------- + +When a cookie withdrawn, a CLOSE request (opcode CACHEFILES_OP_CLOSE) will be +sent to the user daemon. This tells the user daemon to close all anonymous fds +associated with the given object_id. The CLOSE request has no extra payload, +and shouldn't be replied. + + +The READ Request +---------------- + +When a cache miss is encountered in on-demand read mode, CacheFiles will send a +READ request (opcode CACHEFILES_OP_READ) to the user daemon. This tells the user +daemon to fetch the contents of the requested file range. The payload is of the +form:: + + struct cachefiles_read { + __u64 off; + __u64 len; + }; + +where: + + * ``off`` indicates the starting offset of the requested file range. + + * ``len`` indicates the length of the requested file range. + + +When it receives a READ request, the user daemon should fetch the requested data +and write it to the cache file identified by object_id. + +When it has finished processing the READ request, the user daemon should reply +by using the CACHEFILES_IOC_READ_COMPLETE ioctl on one of the anonymous fds +associated with the object_id given in the READ request. The ioctl is of the +form:: + + ioctl(fd, CACHEFILES_IOC_READ_COMPLETE, msg_id); + +where: + + * ``fd`` is one of the anonymous fds associated with the object_id + given. + + * ``msg_id`` must match the msg_id field of the READ request. diff --git a/Documentation/filesystems/caching/netfs-api.rst b/Documentation/filesystems/caching/netfs-api.rst index 7308d76a29dc..1d18e9def183 100644 --- a/Documentation/filesystems/caching/netfs-api.rst +++ b/Documentation/filesystems/caching/netfs-api.rst @@ -433,11 +433,11 @@ has done a write and then the page it wrote from has been released by the VM, after which it *has* to look in the cache. To inform fscache that a page might now be in the cache, the following function -should be called from the ``releasepage`` address space op:: +should be called from the ``release_folio`` address space op:: void fscache_note_page_release(struct fscache_cookie *cookie); -if the page has been released (ie. releasepage returned true). +if the page has been released (ie. release_folio returned true). Page release and page invalidation should also wait for any mark left on the page to say that a DIO write is underway from that page:: diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst index 6ccd5efb25b7..2e9aaa295125 100644 --- a/Documentation/filesystems/fscrypt.rst +++ b/Documentation/filesystems/fscrypt.rst @@ -1256,7 +1256,7 @@ inline encryption hardware will encrypt/decrypt the file contents. When inline encryption isn't used, filesystems must encrypt/decrypt the file contents themselves, as described below: -For the read path (->readpage()) of regular files, filesystems can +For the read path (->read_folio()) of regular files, filesystems can read the ciphertext into the page cache and decrypt it in-place. The page lock must be held until decryption has finished, to prevent the page from becoming visible to userspace prematurely. diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst index 8cc536d08f51..756f2c215ba1 100644 --- a/Documentation/filesystems/fsverity.rst +++ b/Documentation/filesystems/fsverity.rst @@ -70,12 +70,23 @@ must live on a read-write filesystem because they are independently updated and potentially user-installed, so dm-verity cannot be used. The base fs-verity feature is a hashing mechanism only; actually -authenticating the files is up to userspace. However, to meet some -users' needs, fs-verity optionally supports a simple signature -verification mechanism where users can configure the kernel to require -that all fs-verity files be signed by a key loaded into a keyring; see -`Built-in signature verification`_. Support for fs-verity file hashes -in IMA (Integrity Measurement Architecture) policies is also planned. +authenticating the files may be done by: + +* Userspace-only + +* Builtin signature verification + userspace policy + + fs-verity optionally supports a simple signature verification + mechanism where users can configure the kernel to require that + all fs-verity files be signed by a key loaded into a keyring; + see `Built-in signature verification`_. + +* Integrity Measurement Architecture (IMA) + + IMA supports including fs-verity file digests and signatures in the + IMA measurement list and verifying fs-verity based file signatures + stored as security.ima xattrs, based on policy. + User API ======== @@ -548,7 +559,7 @@ already verified). Below, we describe how filesystems implement this. Pagecache ~~~~~~~~~ -For filesystems using Linux's pagecache, the ``->readpage()`` and +For filesystems using Linux's pagecache, the ``->read_folio()`` and ``->readahead()`` methods must be modified to verify pages before they are marked Uptodate. Merely hooking ``->read_iter()`` would be insufficient, since ``->read_iter()`` is not used for memory maps. @@ -653,12 +664,12 @@ weren't already directly answered in other parts of this document. hashed and what to do with those hashes, such as log them, authenticate them, or add them to a measurement list. - IMA is planned to support the fs-verity hashing mechanism as an - alternative to doing full file hashes, for people who want the - performance and security benefits of the Merkle tree based hash. - But it doesn't make sense to force all uses of fs-verity to be - through IMA. As a standalone filesystem feature, fs-verity - already meets many users' needs, and it's testable like other + IMA supports the fs-verity hashing mechanism as an alternative + to full file hashes, for those who want the performance and + security benefits of the Merkle tree based hash. However, it + doesn't make sense to force all uses of fs-verity to be through + IMA. fs-verity already meets many users' needs even as a + standalone filesystem feature, and it's testable like other filesystem features e.g. with xfstests. :Q: Isn't fs-verity useless because the attacker can just modify the diff --git a/Documentation/filesystems/idmappings.rst b/Documentation/filesystems/idmappings.rst index 7a879ec3b6bf..c1db8748389c 100644 --- a/Documentation/filesystems/idmappings.rst +++ b/Documentation/filesystems/idmappings.rst @@ -369,6 +369,11 @@ 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. +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 +they can solve the problems we observed before. + Example 1 ~~~~~~~~~ diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index c26d854275a0..c0fe711f14d3 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -237,20 +237,20 @@ address_space_operations prototypes:: int (*writepage)(struct page *page, struct writeback_control *wbc); - int (*readpage)(struct file *, struct page *); + int (*read_folio)(struct file *, struct folio *); int (*writepages)(struct address_space *, struct writeback_control *); bool (*dirty_folio)(struct address_space *, struct folio *folio); void (*readahead)(struct readahead_control *); int (*write_begin)(struct file *, struct address_space *mapping, - loff_t pos, unsigned len, unsigned flags, + loff_t pos, unsigned len, struct page **pagep, void **fsdata); int (*write_end)(struct file *, struct address_space *mapping, loff_t pos, unsigned len, unsigned copied, struct page *page, void *fsdata); sector_t (*bmap)(struct address_space *, sector_t); void (*invalidate_folio) (struct folio *, size_t start, size_t len); - int (*releasepage) (struct page *, int); - void (*freepage)(struct page *); + bool (*release_folio)(struct folio *, gfp_t); + void (*free_folio)(struct folio *); int (*direct_IO)(struct kiocb *, struct iov_iter *iter); bool (*isolate_page) (struct page *, isolate_mode_t); int (*migratepage)(struct address_space *, struct page *, struct page *); @@ -258,26 +258,27 @@ prototypes:: int (*launder_folio)(struct folio *); bool (*is_partially_uptodate)(struct folio *, size_t from, size_t count); int (*error_remove_page)(struct address_space *, struct page *); - int (*swap_activate)(struct file *); + int (*swap_activate)(struct swap_info_struct *sis, struct file *f, sector_t *span) int (*swap_deactivate)(struct file *); + int (*swap_rw)(struct kiocb *iocb, struct iov_iter *iter); locking rules: - All except dirty_folio and freepage may block + All except dirty_folio and free_folio may block ====================== ======================== ========= =============== -ops PageLocked(page) i_rwsem invalidate_lock +ops folio locked i_rwsem invalidate_lock ====================== ======================== ========= =============== writepage: yes, unlocks (see below) -readpage: yes, unlocks shared +read_folio: yes, unlocks shared writepages: -dirty_folio maybe +dirty_folio: maybe readahead: yes, unlocks shared write_begin: locks the page exclusive write_end: yes, unlocks exclusive bmap: invalidate_folio: yes exclusive -releasepage: yes -freepage: yes +release_folio: yes +free_folio: yes direct_IO: isolate_page: yes migratepage: yes (both) @@ -287,15 +288,16 @@ is_partially_uptodate: yes error_remove_page: yes swap_activate: no swap_deactivate: no +swap_rw: yes, unlocks ====================== ======================== ========= =============== -->write_begin(), ->write_end() and ->readpage() may be called from +->write_begin(), ->write_end() and ->read_folio() may be called from the request handler (/dev/loop). -->readpage() unlocks the page, either synchronously or via I/O +->read_folio() unlocks the folio, either synchronously or via I/O completion. -->readahead() unlocks the pages that I/O is attempted on like ->readpage(). +->readahead() unlocks the folios that I/O is attempted on like ->read_folio(). ->writepage() is used for two purposes: for "memory cleansing" and for "sync". These are quite different operations and the behaviour may differ @@ -372,12 +374,12 @@ invalidate_lock before invalidating page cache in truncate / hole punch path (and thus calling into ->invalidate_folio) to block races between page cache invalidation and page cache filling functions (fault, read, ...). -->releasepage() is called when the kernel is about to try to drop the -buffers from the page in preparation for freeing it. It returns zero to -indicate that the buffers are (or may be) freeable. If ->releasepage is zero, -the kernel assumes that the fs has no private interest in the buffers. +->release_folio() is called when the kernel is about to try to drop the +buffers from the folio in preparation for freeing it. It returns false to +indicate that the buffers are (or may be) freeable. If ->release_folio is +NULL, the kernel assumes that the fs has no private interest in the buffers. -->freepage() is called when the kernel is done dropping the page +->free_folio() is called when the kernel has dropped the folio from the page cache. ->launder_folio() may be called prior to releasing a folio if @@ -386,15 +388,19 @@ cleaned, or an error value if not. Note that in order to prevent the folio getting mapped back in and redirtied, it needs to be kept locked across the entire operation. -->swap_activate will be called with a non-zero argument on -files backing (non block device backed) swapfiles. A return value -of zero indicates success, in which case this file can be used for -backing swapspace. The swapspace operations will be proxied to the -address space operations. +->swap_activate() will be called to prepare the given file for swap. It +should perform any validation and preparation necessary to ensure that +writes can be performed with minimal memory allocation. It should call +add_swap_extent(), or the helper iomap_swapfile_activate(), and return +the number of extents added. If IO should be submitted through +->swap_rw(), it should set SWP_FS_OPS, otherwise IO will be submitted +directly to the block device ``sis->bdev``. ->swap_deactivate() will be called in the sys_swapoff() path after ->swap_activate() returned success. +->swap_rw will be called for swap IO if SWP_FS_OPS was set by ->swap_activate(). + file_lock_operations ==================== @@ -428,6 +434,8 @@ prototypes:: void (*lm_break)(struct file_lock *); /* break_lease callback */ int (*lm_change)(struct file_lock **, int); bool (*lm_breaker_owns_lease)(struct file_lock *); + bool (*lm_lock_expirable)(struct file_lock *); + void (*lm_expire_lock)(void); locking rules: @@ -439,6 +447,8 @@ lm_grant: no no no lm_break: yes no no lm_change yes no no lm_breaker_owns_lease: yes no no +lm_lock_expirable yes no no +lm_expire_lock no no yes ====================== ============= ================= ========= buffer_head diff --git a/Documentation/filesystems/netfs_library.rst b/Documentation/filesystems/netfs_library.rst index 69f00179fdfe..a80a59941d2f 100644 --- a/Documentation/filesystems/netfs_library.rst +++ b/Documentation/filesystems/netfs_library.rst @@ -96,7 +96,7 @@ attached to an inode (or NULL if fscache is disabled):: Buffered Read Helpers ===================== -The library provides a set of read helpers that handle the ->readpage(), +The library provides a set of read helpers that handle the ->read_folio(), ->readahead() and much of the ->write_begin() VM operations and translate them into a common call framework. @@ -136,20 +136,19 @@ Read Helper Functions Three read helpers are provided:: void netfs_readahead(struct readahead_control *ractl); - int netfs_readpage(struct file *file, - struct page *page); + int netfs_read_folio(struct file *file, + struct folio *folio); int netfs_write_begin(struct file *file, struct address_space *mapping, loff_t pos, unsigned int len, - unsigned int flags, struct folio **_folio, void **_fsdata); Each corresponds to a VM address space operation. These operations use the state in the per-inode context. -For ->readahead() and ->readpage(), the network filesystem just point directly +For ->readahead() and ->read_folio(), the network filesystem just point directly at the corresponding read helper; whereas for ->write_begin(), it may be a little more complicated as the network filesystem might want to flush conflicting writes or track dirty data and needs to put the acquired folio if diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst index 7c1583dbeb59..2e0e4f0e0c6f 100644 --- a/Documentation/filesystems/porting.rst +++ b/Documentation/filesystems/porting.rst @@ -624,7 +624,7 @@ any symlink that might use page_follow_link_light/page_put_link() must have inode_nohighmem(inode) called before anything might start playing with its pagecache. No highmem pages should end up in the pagecache of such symlinks. That includes any preseeding that might be done during symlink -creation. __page_symlink() will honour the mapping gfp flags, so once +creation. page_symlink() will honour the mapping gfp flags, so once you've done inode_nohighmem() it's safe to use, but if you allocate and insert the page manually, make sure to use the right gfp flags. diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 061744c436d9..1bc91fb8c321 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -942,56 +942,73 @@ can be substantial. In many cases there are other means to find out additional memory using subsystem specific interfaces, for instance /proc/net/sockstat for TCP memory allocations. -The following is from a 16GB PIII, which has highmem enabled. -You may not have all of these fields. +Example output. You may not have all of these fields. :: > cat /proc/meminfo - MemTotal: 16344972 kB - MemFree: 13634064 kB - MemAvailable: 14836172 kB - Buffers: 3656 kB - Cached: 1195708 kB - SwapCached: 0 kB - Active: 891636 kB - Inactive: 1077224 kB - HighTotal: 15597528 kB - HighFree: 13629632 kB - LowTotal: 747444 kB - LowFree: 4432 kB - SwapTotal: 0 kB - SwapFree: 0 kB - Dirty: 968 kB - Writeback: 0 kB - AnonPages: 861800 kB - Mapped: 280372 kB - Shmem: 644 kB - KReclaimable: 168048 kB - Slab: 284364 kB - SReclaimable: 159856 kB - SUnreclaim: 124508 kB - PageTables: 24448 kB - NFS_Unstable: 0 kB - Bounce: 0 kB - WritebackTmp: 0 kB - CommitLimit: 7669796 kB - Committed_AS: 100056 kB - VmallocTotal: 112216 kB - VmallocUsed: 428 kB - VmallocChunk: 111088 kB - Percpu: 62080 kB - HardwareCorrupted: 0 kB - AnonHugePages: 49152 kB - ShmemHugePages: 0 kB - ShmemPmdMapped: 0 kB + MemTotal: 32858820 kB + MemFree: 21001236 kB + MemAvailable: 27214312 kB + Buffers: 581092 kB + Cached: 5587612 kB + SwapCached: 0 kB + Active: 3237152 kB + Inactive: 7586256 kB + Active(anon): 94064 kB + Inactive(anon): 4570616 kB + Active(file): 3143088 kB + Inactive(file): 3015640 kB + Unevictable: 0 kB + Mlocked: 0 kB + SwapTotal: 0 kB + SwapFree: 0 kB + Zswap: 1904 kB + Zswapped: 7792 kB + Dirty: 12 kB + Writeback: 0 kB + AnonPages: 4654780 kB + Mapped: 266244 kB + Shmem: 9976 kB + KReclaimable: 517708 kB + Slab: 660044 kB + SReclaimable: 517708 kB + SUnreclaim: 142336 kB + KernelStack: 11168 kB + PageTables: 20540 kB + NFS_Unstable: 0 kB + Bounce: 0 kB + WritebackTmp: 0 kB + CommitLimit: 16429408 kB + Committed_AS: 7715148 kB + VmallocTotal: 34359738367 kB + VmallocUsed: 40444 kB + VmallocChunk: 0 kB + Percpu: 29312 kB + HardwareCorrupted: 0 kB + AnonHugePages: 4149248 kB + ShmemHugePages: 0 kB + ShmemPmdMapped: 0 kB + FileHugePages: 0 kB + FilePmdMapped: 0 kB + CmaTotal: 0 kB + CmaFree: 0 kB + HugePages_Total: 0 + HugePages_Free: 0 + HugePages_Rsvd: 0 + HugePages_Surp: 0 + Hugepagesize: 2048 kB + Hugetlb: 0 kB + DirectMap4k: 401152 kB + DirectMap2M: 10008576 kB + DirectMap1G: 24117248 kB MemTotal Total usable RAM (i.e. physical RAM minus a few reserved bits and the kernel binary code) MemFree - The sum of LowFree+HighFree + Total free RAM. On highmem systems, the sum of LowFree+HighFree MemAvailable An estimate of how much memory is available for starting new applications, without swapping. Calculated from MemFree, @@ -1005,8 +1022,9 @@ Buffers Relatively temporary storage for raw disk blocks shouldn't get tremendously large (20MB or so) Cached - in-memory cache for files read from the disk (the - pagecache). Doesn't include SwapCached + In-memory cache for files read from the disk (the + pagecache) as well as tmpfs & shmem. + Doesn't include SwapCached. SwapCached Memory that once was swapped out, is swapped back in but still also is in the swapfile (if memory is needed it @@ -1018,6 +1036,11 @@ Active Inactive Memory which has been less recently used. It is more eligible to be reclaimed for other purposes +Unevictable + Memory allocated for userspace which cannot be reclaimed, such + as mlocked pages, ramfs backing pages, secret memfd pages etc. +Mlocked + Memory locked with mlock(). HighTotal, HighFree Highmem is all memory above ~860MB of physical memory. Highmem areas are for use by userspace programs, or @@ -1034,26 +1057,20 @@ SwapTotal SwapFree Memory which has been evicted from RAM, and is temporarily on the disk +Zswap + Memory consumed by the zswap backend (compressed size) +Zswapped + Amount of anonymous memory stored in zswap (original size) Dirty Memory which is waiting to get written back to the disk Writeback Memory which is actively being written back to the disk AnonPages Non-file backed pages mapped into userspace page tables -HardwareCorrupted - The amount of RAM/memory in KB, the kernel identifies as - corrupted. -AnonHugePages - Non-file backed huge pages mapped into userspace page tables Mapped files which have been mmaped, such as libraries Shmem Total memory used by shared memory (shmem) and tmpfs -ShmemHugePages - Memory used by shared memory (shmem) and tmpfs allocated - with huge pages -ShmemPmdMapped - Shared memory mapped into userspace with huge pages KReclaimable Kernel allocations that the kernel will attempt to reclaim under memory pressure. Includes SReclaimable (below), and other @@ -1064,9 +1081,10 @@ SReclaimable Part of Slab, that might be reclaimed, such as caches SUnreclaim Part of Slab, that cannot be reclaimed on memory pressure +KernelStack + Memory consumed by the kernel stacks of all tasks PageTables - amount of memory dedicated to the lowest level of page - tables. + Memory consumed by userspace page tables NFS_Unstable Always zero. Previous counted pages which had been written to the server, but has not been committed to stable storage. @@ -1098,7 +1116,7 @@ Committed_AS has been allocated by processes, even if it has not been "used" by them as of yet. A process which malloc()'s 1G of memory, but only touches 300M of it will show up as - using 1G. This 1G is memory which has been "committed" to + using 1G. This 1G is memory which has been "committed" to by the VM and can be used at any time by the allocating application. With strict overcommit enabled on the system (mode 2 in 'vm.overcommit_memory'), allocations which would @@ -1107,7 +1125,7 @@ Committed_AS not fail due to lack of memory once that memory has been successfully allocated. VmallocTotal - total size of vmalloc memory area + total size of vmalloc virtual address space VmallocUsed amount of vmalloc area which is used VmallocChunk @@ -1115,6 +1133,30 @@ VmallocChunk Percpu Memory allocated to the percpu allocator used to back percpu allocations. This stat excludes the cost of metadata. +HardwareCorrupted + The amount of RAM/memory in KB, the kernel identifies as + corrupted. +AnonHugePages + Non-file backed huge pages mapped into userspace page tables +ShmemHugePages + Memory used by shared memory (shmem) and tmpfs allocated + with huge pages +ShmemPmdMapped + Shared memory mapped into userspace with huge pages +FileHugePages + Memory used for filesystem data (page cache) allocated + with huge pages +FilePmdMapped + Page cache mapped into userspace with huge pages +CmaTotal + Memory reserved for the Contiguous Memory Allocator (CMA) +CmaFree + Free remaining memory in the CMA reserves +HugePages_Total, HugePages_Free, HugePages_Rsvd, HugePages_Surp, Hugepagesize, Hugetlb + See Documentation/admin-guide/mm/hugetlbpage.rst. +DirectMap4k, DirectMap2M, DirectMap1G + Breakdown of page table sizes used in the kernel's + identity mapping of RAM vmallocinfo ~~~~~~~~~~~ @@ -1183,85 +1225,7 @@ Provides counts of softirq handlers serviced since boot time, for each CPU. HRTIMER: 0 0 0 0 RCU: 1678 1769 2178 2250 - -1.3 IDE devices in /proc/ide ----------------------------- - -The subdirectory /proc/ide contains information about all IDE devices of which -the kernel is aware. There is one subdirectory for each IDE controller, the -file drivers and a link for each IDE device, pointing to the device directory -in the controller specific subtree. - -The file 'drivers' contains general information about the drivers used for the -IDE devices:: - - > cat /proc/ide/drivers - ide-cdrom version 4.53 - ide-disk version 1.08 - -More detailed information can be found in the controller specific -subdirectories. These are named ide0, ide1 and so on. Each of these -directories contains the files shown in table 1-6. - - -.. table:: Table 1-6: IDE controller info in /proc/ide/ide? - - ======= ======================================= - File Content - ======= ======================================= - channel IDE channel (0 or 1) - config Configuration (only for PCI/IDE bridge) - mate Mate name - model Type/Chipset of IDE controller - ======= ======================================= - -Each device connected to a controller has a separate subdirectory in the -controllers directory. The files listed in table 1-7 are contained in these -directories. - - -.. table:: Table 1-7: IDE device information - - ================ ========================================== - File Content - ================ ========================================== - cache The cache - capacity Capacity of the medium (in 512Byte blocks) - driver driver and version - geometry physical and logical geometry - identify device identify block - media media type - model device identifier - settings device setup - smart_thresholds IDE disk management thresholds - smart_values IDE disk management values - ================ ========================================== - -The most interesting file is ``settings``. This file contains a nice -overview of the drive parameters:: - - # cat /proc/ide/ide0/hda/settings - name value min max mode - ---- ----- --- --- ---- - bios_cyl 526 0 65535 rw - bios_head 255 0 255 rw - bios_sect 63 0 63 rw - breada_readahead 4 0 127 rw - bswap 0 0 1 r - file_readahead 72 0 2097151 rw - io_32bit 0 0 3 rw - keepsettings 0 0 1 rw - max_kb_per_request 122 1 127 rw - multcount 0 0 8 rw - nice1 1 0 1 rw - nowerr 0 0 1 rw - pio_mode write-only 0 255 w - slow 0 0 1 rw - unmaskirq 0 0 1 rw - using_dma 0 0 1 rw - - -1.4 Networking info in /proc/net +1.3 Networking info in /proc/net -------------------------------- The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the @@ -1340,7 +1304,7 @@ It will contain information that is specific to that bond, such as the current slaves of the bond, the link status of the slaves, and how many times the slaves link has failed. -1.5 SCSI info +1.4 SCSI info ------------- If you have a SCSI host adapter in your system, you'll find a subdirectory @@ -1403,7 +1367,7 @@ AHA-2940 SCSI adapter:: Total transfers 0 (0 reads and 0 writes) -1.6 Parallel port info in /proc/parport +1.5 Parallel port info in /proc/parport --------------------------------------- The directory /proc/parport contains information about the parallel ports of @@ -1428,7 +1392,7 @@ These directories contain the four files shown in Table 1-10. number or none). ========= ==================================================================== -1.7 TTY info in /proc/tty +1.6 TTY info in /proc/tty ------------------------- Information about the available and actually used tty's can be found in the @@ -1463,7 +1427,7 @@ To see which tty's are currently in use, you can simply look into the file unknown /dev/tty 4 1-63 console -1.8 Miscellaneous kernel statistics in /proc/stat +1.7 Miscellaneous kernel statistics in /proc/stat ------------------------------------------------- Various pieces of information about kernel activity are available in the @@ -1536,7 +1500,7 @@ softirqs serviced; each subsequent column is the total for that particular softirq. -1.9 Ext4 file system parameters +1.8 Ext4 file system parameters ------------------------------- Information about mounted ext4 file systems can be found in @@ -1552,7 +1516,7 @@ in Table 1-12, below. mb_groups details of multiblock allocator buddy cache of free blocks ============== ========================================================== -1.10 /proc/consoles +1.9 /proc/consoles ------------------- Shows registered system console lines. diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index 794bd1a66bfb..08069ecd49a6 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -620,9 +620,9 @@ Writeback. The first can be used independently to the others. The VM can try to either write dirty pages in order to clean them, or release clean pages in order to reuse them. To do this it can call the ->writepage method -on dirty pages, and ->releasepage on clean pages with PagePrivate set. -Clean pages without PagePrivate and with no external references will be -released without notice being given to the address_space. +on dirty pages, and ->release_folio on clean folios with the private +flag set. Clean pages without PagePrivate and with no external references +will be released without notice being given to the address_space. To achieve this functionality, pages need to be placed on an LRU with lru_cache_add and mark_page_active needs to be called whenever the page @@ -656,7 +656,7 @@ by memory-mapping the page. Data is written into the address space by the application, and then written-back to storage typically in whole pages, however the address_space has finer control of write sizes. -The read process essentially only requires 'readpage'. The write +The read process essentially only requires 'read_folio'. The write process is more complicated and uses write_begin/write_end or dirty_folio to write data into the address_space, and writepage and writepages to writeback data to storage. @@ -722,20 +722,20 @@ cache in your filesystem. The following members are defined: struct address_space_operations { int (*writepage)(struct page *page, struct writeback_control *wbc); - int (*readpage)(struct file *, struct page *); + int (*read_folio)(struct file *, struct folio *); int (*writepages)(struct address_space *, struct writeback_control *); bool (*dirty_folio)(struct address_space *, struct folio *); void (*readahead)(struct readahead_control *); int (*write_begin)(struct file *, struct address_space *mapping, - loff_t pos, unsigned len, unsigned flags, + loff_t pos, unsigned len, struct page **pagep, void **fsdata); int (*write_end)(struct file *, struct address_space *mapping, loff_t pos, unsigned len, unsigned copied, struct page *page, void *fsdata); sector_t (*bmap)(struct address_space *, sector_t); void (*invalidate_folio) (struct folio *, size_t start, size_t len); - int (*releasepage) (struct page *, int); - void (*freepage)(struct page *); + bool (*release_folio)(struct folio *, gfp_t); + void (*free_folio)(struct folio *); ssize_t (*direct_IO)(struct kiocb *, struct iov_iter *iter); /* isolate a page for migration */ bool (*isolate_page) (struct page *, isolate_mode_t); @@ -747,10 +747,11 @@ cache in your filesystem. The following members are defined: bool (*is_partially_uptodate) (struct folio *, size_t from, size_t count); - void (*is_dirty_writeback) (struct page *, bool *, bool *); + void (*is_dirty_writeback)(struct folio *, bool *, bool *); int (*error_remove_page) (struct mapping *mapping, struct page *page); - int (*swap_activate)(struct file *); + int (*swap_activate)(struct swap_info_struct *sis, struct file *f, sector_t *span) int (*swap_deactivate)(struct file *); + int (*swap_rw)(struct kiocb *iocb, struct iov_iter *iter); }; ``writepage`` @@ -772,14 +773,14 @@ cache in your filesystem. The following members are defined: See the file "Locking" for more details. -``readpage`` - called by the VM to read a page from backing store. The page - will be Locked when readpage is called, and should be unlocked - and marked uptodate once the read completes. If ->readpage - discovers that it needs to unlock the page for some reason, it - can do so, and then return AOP_TRUNCATED_PAGE. In this case, - the page will be relocated, relocked and if that all succeeds, - ->readpage will be called again. +``read_folio`` + called by the VM to read a folio from backing store. The folio + will be locked when read_folio is called, and should be unlocked + and marked uptodate once the read completes. If ->read_folio + discovers that it cannot perform the I/O at this time, it can + unlock the folio and return AOP_TRUNCATED_PAGE. In this case, + the folio will be looked up again, relocked and if that all succeeds, + ->read_folio will be called again. ``writepages`` called by the VM to write out pages associated with the @@ -832,9 +833,6 @@ cache in your filesystem. The following members are defined: passed to write_begin is greater than the number of bytes copied into the page). - flags is a field for AOP_FLAG_xxx flags, described in - include/linux/fs.h. - A void * may be returned in fsdata, which then gets passed into write_end. @@ -867,36 +865,35 @@ cache in your filesystem. The following members are defined: address space. This generally corresponds to either a truncation, punch hole or a complete invalidation of the address space (in the latter case 'offset' will always be 0 and 'length' - will be folio_size()). Any private data associated with the page + will be folio_size()). Any private data associated with the folio should be updated to reflect this truncation. If offset is 0 and length is folio_size(), then the private data should be - released, because the page must be able to be completely - discarded. This may be done by calling the ->releasepage + released, because the folio must be able to be completely + discarded. This may be done by calling the ->release_folio function, but in this case the release MUST succeed. -``releasepage`` - releasepage is called on PagePrivate pages to indicate that the - page should be freed if possible. ->releasepage should remove - any private data from the page and clear the PagePrivate flag. - If releasepage() fails for some reason, it must indicate failure - with a 0 return value. releasepage() is used in two distinct - though related cases. The first is when the VM finds a clean - page with no active users and wants to make it a free page. If - ->releasepage succeeds, the page will be removed from the - address_space and become free. +``release_folio`` + release_folio is called on folios with private data to tell the + filesystem that the folio is about to be freed. ->release_folio + should remove any private data from the folio and clear the + private flag. If release_folio() fails, it should return false. + release_folio() is used in two distinct though related cases. + The first is when the VM wants to free a clean folio with no + active users. If ->release_folio succeeds, the folio will be + removed from the address_space and be freed. The second case is when a request has been made to invalidate - some or all pages in an address_space. This can happen through - the fadvise(POSIX_FADV_DONTNEED) system call or by the - filesystem explicitly requesting it as nfs and 9fs do (when they + some or all folios in an address_space. This can happen + through the fadvise(POSIX_FADV_DONTNEED) system call or by the + filesystem explicitly requesting it as nfs and 9p do (when they believe the cache may be out of date with storage) by calling invalidate_inode_pages2(). If the filesystem makes such a call, - and needs to be certain that all pages are invalidated, then its - releasepage will need to ensure this. Possibly it can clear the - PageUptodate bit if it cannot free private data yet. + and needs to be certain that all folios are invalidated, then + its release_folio will need to ensure this. Possibly it can + clear the uptodate flag if it cannot free private data yet. -``freepage`` - freepage is called once the page is no longer visible in the +``free_folio`` + free_folio is called once the folio is no longer visible in the page cache in order to allow the cleanup of any private data. Since it may be called by the memory reclaimer, it should not assume that the original address_space mapping still exists, and @@ -935,14 +932,14 @@ cache in your filesystem. The following members are defined: without needing I/O to bring the whole page up to date. ``is_dirty_writeback`` - Called by the VM when attempting to reclaim a page. The VM uses + Called by the VM when attempting to reclaim a folio. The VM uses dirty and writeback information to determine if it needs to stall to allow flushers a chance to complete some IO. - Ordinarily it can use PageDirty and PageWriteback but some - filesystems have more complex state (unstable pages in NFS + Ordinarily it can use folio_test_dirty and folio_test_writeback but + some filesystems have more complex state (unstable folios in NFS prevent reclaim) or do not set those flags due to locking problems. This callback allows a filesystem to indicate to the - VM if a page should be treated as dirty or writeback for the + VM if a folio should be treated as dirty or writeback for the purposes of stalling. ``error_remove_page`` @@ -952,15 +949,21 @@ cache in your filesystem. The following members are defined: unless you have them locked or reference counts increased. ``swap_activate`` - Called when swapon is used on a file to allocate space if - necessary and pin the block lookup information in memory. A - return value of zero indicates success, in which case this file - can be used to back swapspace. + + Called to prepare the given file for swap. It should perform + any validation and preparation necessary to ensure that writes + can be performed with minimal memory allocation. It should call + add_swap_extent(), or the helper iomap_swapfile_activate(), and + return the number of extents added. If IO should be submitted + through ->swap_rw(), it should set SWP_FS_OPS, otherwise IO will + be submitted directly to the block device ``sis->bdev``. ``swap_deactivate`` Called during swapoff on files where swap_activate was successful. +``swap_rw`` + Called to read or write swap pages when SWP_FS_OPS is set. The File Object =============== diff --git a/Documentation/filesystems/zonefs.rst b/Documentation/filesystems/zonefs.rst index 6b213fe9a33e..394b9f15dce0 100644 --- a/Documentation/filesystems/zonefs.rst +++ b/Documentation/filesystems/zonefs.rst @@ -306,8 +306,15 @@ Further notes: Mount options ------------- -zonefs define the "errors=<behavior>" mount option to allow the user to specify -zonefs behavior in response to I/O errors, inode size inconsistencies or zone +zonefs defines several mount options: +* errors=<behavior> +* explicit-open + +"errors=<behavior>" option +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The "errors=<behavior>" option mount option allows the user to specify zonefs +behavior in response to I/O errors, inode size inconsistencies or zone condition changes. The defined behaviors are as follow: * remount-ro (default) @@ -326,6 +333,9 @@ discover the amount of data that has been written to the zone. In the case of a read-only zone discovered at run-time, as indicated in the previous section. The size of the zone file is left unchanged from its last updated value. +"explicit-open" option +~~~~~~~~~~~~~~~~~~~~~~ + A zoned block device (e.g. an NVMe Zoned Namespace device) may have limits on the number of zones that can be active, that is, zones that are in the implicit open, explicit open or closed conditions. This potential limitation @@ -341,6 +351,44 @@ guaranteed that write requests can be processed. Conversely, the to the device on the last close() of a zone file if the zone is not full nor empty. +Runtime sysfs attributes +------------------------ + +zonefs defines several sysfs attributes for mounted devices. All attributes +are user readable and can be found in the directory /sys/fs/zonefs/<dev>/, +where <dev> is the name of the mounted zoned block device. + +The attributes defined are as follows. + +* **max_wro_seq_files**: This attribute reports the maximum number of + sequential zone files that can be open for writing. This number corresponds + to the maximum number of explicitly or implicitly open zones that the device + supports. A value of 0 means that the device has no limit and that any zone + (any file) can be open for writing and written at any time, regardless of the + state of other zones. When the *explicit-open* mount option is used, zonefs + will fail any open() system call requesting to open a sequential zone file for + writing when the number of sequential zone files already open for writing has + reached the *max_wro_seq_files* limit. +* **nr_wro_seq_files**: This attribute reports the current number of sequential + zone files open for writing. When the "explicit-open" mount option is used, + this number can never exceed *max_wro_seq_files*. If the *explicit-open* + mount option is not used, the reported number can be greater than + *max_wro_seq_files*. In such case, it is the responsibility of the + application to not write simultaneously more than *max_wro_seq_files* + sequential zone files. Failure to do so can result in write errors. +* **max_active_seq_files**: This attribute reports the maximum number of + sequential zone files that are in an active state, that is, sequential zone + files that are partially writen (not empty nor full) or that have a zone that + is explicitly open (which happens only if the *explicit-open* mount option is + used). This number is always equal to the maximum number of active zones that + the device supports. A value of 0 means that the mounted device has no limit + on the number of sequential zone files that can be active. +* **nr_active_seq_files**: This attributes reports the current number of + sequential zone files that are active. If *max_active_seq_files* is not 0, + then the value of *nr_active_seq_files* can never exceed the value of + *nr_active_seq_files*, regardless of the use of the *explicit-open* mount + option. + Zonefs User Space Tools ======================= |