diff options
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/00-INDEX | 4 | ||||
| -rw-r--r-- | Documentation/filesystems/debugfs.txt | 4 | ||||
| -rw-r--r-- | Documentation/filesystems/efivarfs.txt | 16 | ||||
| -rw-r--r-- | Documentation/filesystems/ext4.txt | 19 | ||||
| -rw-r--r-- | Documentation/filesystems/f2fs.txt | 421 | ||||
| -rw-r--r-- | Documentation/filesystems/jfs.txt | 19 | ||||
| -rw-r--r-- | Documentation/filesystems/nfs/nfs.txt | 44 | ||||
| -rw-r--r-- | Documentation/filesystems/nfs/nfsd-admin-interfaces.txt | 41 | ||||
| -rw-r--r-- | Documentation/filesystems/nfs/nfsroot.txt | 10 | ||||
| -rw-r--r-- | Documentation/filesystems/proc.txt | 138 | ||||
| -rw-r--r-- | Documentation/filesystems/vfat.txt | 9 | ||||
| -rw-r--r-- | Documentation/filesystems/xfs.txt | 13 |
12 files changed, 710 insertions, 28 deletions
diff --git a/Documentation/filesystems/00-INDEX b/Documentation/filesystems/00-INDEX index 8c624a18f67..8042050eb26 100644 --- a/Documentation/filesystems/00-INDEX +++ b/Documentation/filesystems/00-INDEX @@ -38,6 +38,8 @@ dnotify_test.c - example program for dnotify ecryptfs.txt - docs on eCryptfs: stacked cryptographic filesystem for Linux. +efivarfs.txt + - info for the efivarfs filesystem. exofs.txt - info, usage, mount options, design about EXOFS. ext2.txt @@ -48,6 +50,8 @@ ext4.txt - info, mount options and specifications for the Ext4 filesystem. files.txt - info on file management in the Linux kernel. +f2fs.txt + - info and mount options for the F2FS filesystem. fuse.txt - info on the Filesystem in User SpacE including mount options. gfs2.txt diff --git a/Documentation/filesystems/debugfs.txt b/Documentation/filesystems/debugfs.txt index 7a34f827989..3a863f69272 100644 --- a/Documentation/filesystems/debugfs.txt +++ b/Documentation/filesystems/debugfs.txt @@ -15,8 +15,8 @@ Debugfs is typically mounted with a command like: mount -t debugfs none /sys/kernel/debug (Or an equivalent /etc/fstab line). -The debugfs root directory is accessible by anyone by default. To -restrict access to the tree the "uid", "gid" and "mode" mount +The debugfs root directory is accessible only to the root user by +default. To change access to the tree the "uid", "gid" and "mode" mount options can be used. Note that the debugfs API is exported GPL-only to modules. diff --git a/Documentation/filesystems/efivarfs.txt b/Documentation/filesystems/efivarfs.txt new file mode 100644 index 00000000000..c477af086e6 --- /dev/null +++ b/Documentation/filesystems/efivarfs.txt @@ -0,0 +1,16 @@ + +efivarfs - a (U)EFI variable filesystem + +The efivarfs filesystem was created to address the shortcomings of +using entries in sysfs to maintain EFI variables. The old sysfs EFI +variables code only supported variables of up to 1024 bytes. This +limitation existed in version 0.99 of the EFI specification, but was +removed before any full releases. Since variables can now be larger +than a single page, sysfs isn't the best interface for this. + +Variables can be created, deleted and modified with the efivarfs +filesystem. + +efivarfs is typically mounted like this, + + mount -t efivarfs none /sys/firmware/efi/efivars diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt index 1b7f9acbcbb..34ea4f1fa6e 100644 --- a/Documentation/filesystems/ext4.txt +++ b/Documentation/filesystems/ext4.txt @@ -200,12 +200,9 @@ inode_readahead_blks=n This tuning parameter controls the maximum table readahead algorithm will pre-read into the buffer cache. The default value is 32 blocks. -nouser_xattr Disables Extended User Attributes. If you have extended - attribute support enabled in the kernel configuration - (CONFIG_EXT4_FS_XATTR), extended attribute support - is enabled by default on mount. See the attr(5) manual - page and http://acl.bestbits.at/ for more information - about extended attributes. +nouser_xattr Disables Extended User Attributes. See the + attr(5) manual page and http://acl.bestbits.at/ + for more information about extended attributes. noacl This option disables POSIX Access Control List support. If ACL support is enabled in the kernel @@ -375,6 +372,16 @@ dioread_nolock locking. If the dioread_nolock option is specified Because of the restrictions this options comprises it is off by default (e.g. dioread_lock). +max_dir_size_kb=n This limits the size of directories so that any + attempt to expand them beyond the specified + limit in kilobytes will cause an ENOSPC error. + This is useful in memory constrained + environments, where a very large directory can + cause severe performance problems or even + provoke the Out Of Memory killer. (For example, + if there is only 512mb memory available, a 176mb + directory may seriously cramp the system's style.) + i_version Enable 64-bit inode version support. This option is off by default. diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt new file mode 100644 index 00000000000..8fbd8b46ee3 --- /dev/null +++ b/Documentation/filesystems/f2fs.txt @@ -0,0 +1,421 @@ +================================================================================ +WHAT IS Flash-Friendly File System (F2FS)? +================================================================================ + +NAND flash memory-based storage devices, such as SSD, eMMC, and SD cards, have +been equipped on a variety systems ranging from mobile to server systems. Since +they are known to have different characteristics from the conventional rotating +disks, a file system, an upper layer to the storage device, should adapt to the +changes from the sketch in the design level. + +F2FS is a file system exploiting NAND flash memory-based storage devices, which +is based on Log-structured File System (LFS). The design has been focused on +addressing the fundamental issues in LFS, which are snowball effect of wandering +tree and high cleaning overhead. + +Since a NAND flash memory-based storage device shows different characteristic +according to its internal geometry or flash memory management scheme, namely FTL, +F2FS and its tools support various parameters not only for configuring on-disk +layout, but also for selecting allocation and cleaning algorithms. + +The file system formatting tool, "mkfs.f2fs", is available from the following +git tree: +>> git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs-tools.git + +For reporting bugs and sending patches, please use the following mailing list: +>> linux-f2fs-devel@lists.sourceforge.net + +================================================================================ +BACKGROUND AND DESIGN ISSUES +================================================================================ + +Log-structured File System (LFS) +-------------------------------- +"A log-structured file system writes all modifications to disk sequentially in +a log-like structure, thereby speeding up both file writing and crash recovery. +The log is the only structure on disk; it contains indexing information so that +files can be read back from the log efficiently. In order to maintain large free +areas on disk for fast writing, we divide the log into segments and use a +segment cleaner to compress the live information from heavily fragmented +segments." from Rosenblum, M. and Ousterhout, J. K., 1992, "The design and +implementation of a log-structured file system", ACM Trans. Computer Systems +10, 1, 26–52. + +Wandering Tree Problem +---------------------- +In LFS, when a file data is updated and written to the end of log, its direct +pointer block is updated due to the changed location. Then the indirect pointer +block is also updated due to the direct pointer block update. In this manner, +the upper index structures such as inode, inode map, and checkpoint block are +also updated recursively. This problem is called as wandering tree problem [1], +and in order to enhance the performance, it should eliminate or relax the update +propagation as much as possible. + +[1] Bityutskiy, A. 2005. JFFS3 design issues. http://www.linux-mtd.infradead.org/ + +Cleaning Overhead +----------------- +Since LFS is based on out-of-place writes, it produces so many obsolete blocks +scattered across the whole storage. In order to serve new empty log space, it +needs to reclaim these obsolete blocks seamlessly to users. This job is called +as a cleaning process. + +The process consists of three operations as follows. +1. A victim segment is selected through referencing segment usage table. +2. It loads parent index structures of all the data in the victim identified by + segment summary blocks. +3. It checks the cross-reference between the data and its parent index structure. +4. It moves valid data selectively. + +This cleaning job may cause unexpected long delays, so the most important goal +is to hide the latencies to users. And also definitely, it should reduce the +amount of valid data to be moved, and move them quickly as well. + +================================================================================ +KEY FEATURES +================================================================================ + +Flash Awareness +--------------- +- Enlarge the random write area for better performance, but provide the high + spatial locality +- Align FS data structures to the operational units in FTL as best efforts + +Wandering Tree Problem +---------------------- +- Use a term, “node”, that represents inodes as well as various pointer blocks +- Introduce Node Address Table (NAT) containing the locations of all the “node” + blocks; this will cut off the update propagation. + +Cleaning Overhead +----------------- +- Support a background cleaning process +- Support greedy and cost-benefit algorithms for victim selection policies +- Support multi-head logs for static/dynamic hot and cold data separation +- Introduce adaptive logging for efficient block allocation + +================================================================================ +MOUNT OPTIONS +================================================================================ + +background_gc_off Turn off cleaning operations, namely garbage collection, + triggered in background when I/O subsystem is idle. +disable_roll_forward Disable the roll-forward recovery routine +discard Issue discard/TRIM commands when a segment is cleaned. +no_heap Disable heap-style segment allocation which finds free + segments for data from the beginning of main area, while + for node from the end of main area. +nouser_xattr Disable Extended User Attributes. Note: xattr is enabled + by default if CONFIG_F2FS_FS_XATTR is selected. +noacl Disable POSIX Access Control List. Note: acl is enabled + by default if CONFIG_F2FS_FS_POSIX_ACL is selected. +active_logs=%u Support configuring the number of active logs. In the + current design, f2fs supports only 2, 4, and 6 logs. + Default number is 6. +disable_ext_identify Disable the extension list configured by mkfs, so f2fs + does not aware of cold files such as media files. + +================================================================================ +DEBUGFS ENTRIES +================================================================================ + +/sys/kernel/debug/f2fs/ contains information about all the partitions mounted as +f2fs. Each file shows the whole f2fs information. + +/sys/kernel/debug/f2fs/status includes: + - major file system information managed by f2fs currently + - average SIT information about whole segments + - current memory footprint consumed by f2fs. + +================================================================================ +USAGE +================================================================================ + +1. Download userland tools and compile them. + +2. Skip, if f2fs was compiled statically inside kernel. + Otherwise, insert the f2fs.ko module. + # insmod f2fs.ko + +3. Create a directory trying to mount + # mkdir /mnt/f2fs + +4. Format the block device, and then mount as f2fs + # mkfs.f2fs -l label /dev/block_device + # mount -t f2fs /dev/block_device /mnt/f2fs + +Format options +-------------- +-l [label] : Give a volume label, up to 256 unicode name. +-a [0 or 1] : Split start location of each area for heap-based allocation. + 1 is set by default, which performs this. +-o [int] : Set overprovision ratio in percent over volume size. + 5 is set by default. +-s [int] : Set the number of segments per section. + 1 is set by default. +-z [int] : Set the number of sections per zone. + 1 is set by default. +-e [str] : Set basic extension list. e.g. "mp3,gif,mov" + +================================================================================ +DESIGN +================================================================================ + +On-disk Layout +-------------- + +F2FS divides the whole volume into a number of segments, each of which is fixed +to 2MB in size. A section is composed of consecutive segments, and a zone +consists of a set of sections. By default, section and zone sizes are set to one +segment size identically, but users can easily modify the sizes by mkfs. + +F2FS splits the entire volume into six areas, and all the areas except superblock +consists of multiple segments as described below. + + align with the zone size <-| + |-> align with the segment size + _________________________________________________________________________ + | | | Node | Segment | Segment | | + | Superblock | Checkpoint | Address | Info. | Summary | Main | + | (SB) | (CP) | Table (NAT) | Table (SIT) | Area (SSA) | | + |____________|_____2______|______N______|______N______|______N_____|__N___| + . . + . . + . . + ._________________________________________. + |_Segment_|_..._|_Segment_|_..._|_Segment_| + . . + ._________._________ + |_section_|__...__|_ + . . + .________. + |__zone__| + +- Superblock (SB) + : It is located at the beginning of the partition, and there exist two copies + to avoid file system crash. It contains basic partition information and some + default parameters of f2fs. + +- Checkpoint (CP) + : It contains file system information, bitmaps for valid NAT/SIT sets, orphan + inode lists, and summary entries of current active segments. + +- Node Address Table (NAT) + : It is composed of a block address table for all the node blocks stored in + Main area. + +- Segment Information Table (SIT) + : It contains segment information such as valid block count and bitmap for the + validity of all the blocks. + +- Segment Summary Area (SSA) + : It contains summary entries which contains the owner information of all the + data and node blocks stored in Main area. + +- Main Area + : It contains file and directory data including their indices. + +In order to avoid misalignment between file system and flash-based storage, F2FS +aligns the start block address of CP with the segment size. Also, it aligns the +start block address of Main area with the zone size by reserving some segments +in SSA area. + +Reference the following survey for additional technical details. +https://wiki.linaro.org/WorkingGroups/Kernel/Projects/FlashCardSurvey + +File System Metadata Structure +------------------------------ + +F2FS adopts the checkpointing scheme to maintain file system consistency. At +mount time, F2FS first tries to find the last valid checkpoint data by scanning +CP area. In order to reduce the scanning time, F2FS uses only two copies of CP. +One of them always indicates the last valid data, which is called as shadow copy +mechanism. In addition to CP, NAT and SIT also adopt the shadow copy mechanism. + +For file system consistency, each CP points to which NAT and SIT copies are +valid, as shown as below. + + +--------+----------+---------+ + | CP | NAT | SIT | + +--------+----------+---------+ + . . . . + . . . . + . . . . + +-------+-------+--------+--------+--------+--------+ + | CP #0 | CP #1 | NAT #0 | NAT #1 | SIT #0 | SIT #1 | + +-------+-------+--------+--------+--------+--------+ + | ^ ^ + | | | + `----------------------------------------' + +Index Structure +--------------- + +The key data structure to manage the data locations is a "node". Similar to +traditional file structures, F2FS has three types of node: inode, direct node, +indirect node. F2FS assigns 4KB to an inode block which contains 923 data block +indices, two direct node pointers, two indirect node pointers, and one double +indirect node pointer as described below. One direct node block contains 1018 +data blocks, and one indirect node block contains also 1018 node blocks. Thus, +one inode block (i.e., a file) covers: + + 4KB * (923 + 2 * 1018 + 2 * 1018 * 1018 + 1018 * 1018 * 1018) := 3.94TB. + + Inode block (4KB) + |- data (923) + |- direct node (2) + | `- data (1018) + |- indirect node (2) + | `- direct node (1018) + | `- data (1018) + `- double indirect node (1) + `- indirect node (1018) + `- direct node (1018) + `- data (1018) + +Note that, all the node blocks are mapped by NAT which means the location of +each node is translated by the NAT table. In the consideration of the wandering +tree problem, F2FS is able to cut off the propagation of node updates caused by +leaf data writes. + +Directory Structure +------------------- + +A directory entry occupies 11 bytes, which consists of the following attributes. + +- hash hash value of the file name +- ino inode number +- len the length of file name +- type file type such as directory, symlink, etc + +A dentry block consists of 214 dentry slots and file names. Therein a bitmap is +used to represent whether each dentry is valid or not. A dentry block occupies +4KB with the following composition. + + Dentry Block(4 K) = bitmap (27 bytes) + reserved (3 bytes) + + dentries(11 * 214 bytes) + file name (8 * 214 bytes) + + [Bucket] + +--------------------------------+ + |dentry block 1 | dentry block 2 | + +--------------------------------+ + . . + . . + . [Dentry Block Structure: 4KB] . + +--------+----------+----------+------------+ + | bitmap | reserved | dentries | file names | + +--------+----------+----------+------------+ + [Dentry Block: 4KB] . . + . . + . . + +------+------+-----+------+ + | hash | ino | len | type | + +------+------+-----+------+ + [Dentry Structure: 11 bytes] + +F2FS implements multi-level hash tables for directory structure. Each level has +a hash table with dedicated number of hash buckets as shown below. Note that +"A(2B)" means a bucket includes 2 data blocks. + +---------------------- +A : bucket +B : block +N : MAX_DIR_HASH_DEPTH +---------------------- + +level #0 | A(2B) + | +level #1 | A(2B) - A(2B) + | +level #2 | A(2B) - A(2B) - A(2B) - A(2B) + . | . . . . +level #N/2 | A(2B) - A(2B) - A(2B) - A(2B) - A(2B) - ... - A(2B) + . | . . . . +level #N | A(4B) - A(4B) - A(4B) - A(4B) - A(4B) - ... - A(4B) + +The number of blocks and buckets are determined by, + + ,- 2, if n < MAX_DIR_HASH_DEPTH / 2, + # of blocks in level #n = | + `- 4, Otherwise + + ,- 2^n, if n < MAX_DIR_HASH_DEPTH / 2, + # of buckets in level #n = | + `- 2^((MAX_DIR_HASH_DEPTH / 2) - 1), Otherwise + +When F2FS finds a file name in a directory, at first a hash value of the file +name is calculated. Then, F2FS scans the hash table in level #0 to find the +dentry consisting of the file name and its inode number. If not found, F2FS +scans the next hash table in level #1. In this way, F2FS scans hash tables in +each levels incrementally from 1 to N. In each levels F2FS needs to scan only +one bucket determined by the following equation, which shows O(log(# of files)) +complexity. + + bucket number to scan in level #n = (hash value) % (# of buckets in level #n) + +In the case of file creation, F2FS finds empty consecutive slots that cover the +file name. F2FS searches the empty slots in the hash tables of whole levels from +1 to N in the same way as the lookup operation. + +The following figure shows an example of two cases holding children. + --------------> Dir <-------------- + | | + child child + + child - child [hole] - child + + child - child - child [hole] - [hole] - child + + Case 1: Case 2: + Number of children = 6, Number of children = 3, + File size = 7 File size = 7 + +Default Block Allocation +------------------------ + +At runtime, F2FS manages six active logs inside "Main" area: Hot/Warm/Cold node +and Hot/Warm/Cold data. + +- Hot node contains direct node blocks of directories. +- Warm node contains direct node blocks except hot node blocks. +- Cold node contains indirect node blocks +- Hot data contains dentry blocks +- Warm data contains data blocks except hot and cold data blocks +- Cold data contains multimedia data or migrated data blocks + +LFS has two schemes for free space management: threaded log and copy-and-compac- +tion. The copy-and-compaction scheme which is known as cleaning, is well-suited +for devices showing very good sequential write performance, since free segments +are served all the time for writing new data. However, it suffers from cleaning +overhead under high utilization. Contrarily, the threaded log scheme suffers +from random writes, but no cleaning process is needed. F2FS adopts a hybrid +scheme where the copy-and-compaction scheme is adopted by default, but the +policy is dynamically changed to the threaded log scheme according to the file +system status. + +In order to align F2FS with underlying flash-based storage, F2FS allocates a +segment in a unit of section. F2FS expects that the section size would be the +same as the unit size of garbage collection in FTL. Furthermore, with respect +to the mapping granularity in FTL, F2FS allocates each section of the active +logs from different zones as much as possible, since FTL can write the data in +the active logs into one allocation unit according to its mapping granularity. + +Cleaning process +---------------- + +F2FS does cleaning both on demand and in the background. On-demand cleaning is +triggered when there are not enough free segments to serve VFS calls. Background +cleaner is operated by a kernel thread, and triggers the cleaning job when the +system is idle. + +F2FS supports two victim selection policies: greedy and cost-benefit algorithms. +In the greedy algorithm, F2FS selects a victim segment having the smallest number +of valid blocks. In the cost-benefit algorithm, F2FS selects a victim segment +according to the segment age and the number of valid blocks in order to address +log block thrashing problem in the greedy algorithm. F2FS adopts the greedy +algorithm for on-demand cleaner, while background cleaner adopts cost-benefit +algorithm. + +In order to identify whether the data in the victim segment are valid or not, +F2FS manages a bitmap. Each bit represents the validity of a block, and the +bitmap is composed of a bit stream covering whole blocks in main area. diff --git a/Documentation/filesystems/jfs.txt b/Documentation/filesystems/jfs.txt index 26ebde77e82..f7433355394 100644 --- a/Documentation/filesystems/jfs.txt +++ b/Documentation/filesystems/jfs.txt @@ -3,6 +3,7 @@ IBM's Journaled File System (JFS) for Linux JFS Homepage: http://jfs.sourceforge.net/ The following mount options are supported: +(*) == default iocharset=name Character set to use for converting from Unicode to ASCII. The default is to do no conversion. Use @@ -21,12 +22,12 @@ nointegrity Do not write to the journal. The primary use of this option from backup media. The integrity of the volume is not guaranteed if the system abnormally abends. -integrity Default. Commit metadata changes to the journal. Use this - option to remount a volume where the nointegrity option was +integrity(*) Commit metadata changes to the journal. Use this option to + remount a volume where the nointegrity option was previously specified in order to restore normal behavior. errors=continue Keep going on a filesystem error. -errors=remount-ro Default. Remount the filesystem read-only on an error. +errors=remount-ro(*) Remount the filesystem read-only on an error. errors=panic Panic and halt the machine if an error occurs. uid=value Override on-disk uid with specified value @@ -35,7 +36,17 @@ umask=value Override on-disk umask with specified octal value. For directories, the execute bit will be set if the corresponding read bit is set. -Please send bugs, comments, cards and letters to shaggy@linux.vnet.ibm.com. +discard=minlen This enables/disables the use of discard/TRIM commands. +discard The discard/TRIM commands are sent to the underlying +nodiscard(*) block device when blocks are freed. This is useful for SSD + devices and sparse/thinly-provisioned LUNs. The FITRIM ioctl + command is also available together with the nodiscard option. + The value of minlen specifies the minimum blockcount, when + a TRIM command to the block device is considered usefull. + When no value is given to the discard option, it defaults to + 64 blocks, which means 256KiB in JFS. + The minlen value of discard overrides the minlen value given + on an FITRIM ioctl(). The JFS mailing list can be subscribed to by using the link labeled "Mail list Subscribe" at our web page http://jfs.sourceforge.net/ diff --git a/Documentation/filesystems/nfs/nfs.txt b/Documentation/filesystems/nfs/nfs.txt index f50f26ce6cd..f2571c8bef7 100644 --- a/Documentation/filesystems/nfs/nfs.txt +++ b/Documentation/filesystems/nfs/nfs.txt @@ -12,9 +12,47 @@ and work is in progress on adding support for minor version 1 of the NFSv4 protocol. The purpose of this document is to provide information on some of the -upcall interfaces that are used in order to provide the NFS client with -some of the information that it requires in order to fully comply with -the NFS spec. +special features of the NFS client that can be configured by system +administrators. + + +The nfs4_unique_id parameter +============================ + +NFSv4 requires clients to identify themselves to servers with a unique +string. File open and lock state shared between one client and one server +is associated with this identity. To support robust NFSv4 state recovery +and transparent state migration, this identity string must not change +across client reboots. + +Without any other intervention, the Linux client uses a string that contains +the local system's node name. System administrators, however, often do not +take care to ensure that node names are fully qualified and do not change +over the lifetime of a client system. Node names can have other +administrative requirements that require particular behavior that does not +work well as part of an nfs_client_id4 string. + +The nfs.nfs4_unique_id boot parameter specifies a unique string that can be +used instead of a system's node name when an NFS client identifies itself to +a server. Thus, if the system's node name is not unique, or it changes, its +nfs.nfs4_unique_id stays the same, preventing collision with other clients +or loss of state during NFS reboot recovery or transparent state migration. + +The nfs.nfs4_unique_id string is typically a UUID, though it can contain +anything that is believed to be unique across all NFS clients. An +nfs4_unique_id string should be chosen when a client system is installed, +just as a system's root file system gets a fresh UUID in its label at +install time. + +The string should remain fixed for the lifetime of the client. It can be +changed safely if care is taken that the client shuts down cleanly and all +outstanding NFSv4 state has expired, to prevent loss of NFSv4 state. + +This string can be stored in an NFS client's grub.conf, or it can be provided +via a net boot facility such as PXE. It may also be specified as an nfs.ko +module parameter. Specifying a uniquifier string is not support for NFS +clients running in containers. + The DNS resolver ================ diff --git a/Documentation/filesystems/nfs/nfsd-admin-interfaces.txt b/Documentation/filesystems/nfs/nfsd-admin-interfaces.txt new file mode 100644 index 00000000000..56a96fb08a7 --- /dev/null +++ b/Documentation/filesystems/nfs/nfsd-admin-interfaces.txt @@ -0,0 +1,41 @@ +Administrative interfaces for nfsd +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Note that normally these interfaces are used only by the utilities in +nfs-utils. + +nfsd is controlled mainly by pseudofiles under the "nfsd" filesystem, +which is normally mounted at /proc/fs/nfsd/. + +The server is always started by the first write of a nonzero value to +nfsd/threads. + +Before doing that, NFSD can be told which sockets to listen on by +writing to nfsd/portlist; that write may be: + + - an ascii-encoded file descriptor, which should refer to a + bound (and listening, for tcp) socket, or + - "transportname port", where transportname is currently either + "udp", "tcp", or "rdma". + +If nfsd is started without doing any of these, then it will create one +udp and one tcp listener at port 2049 (see nfsd_init_socks). + +On startup, nfsd and lockd grace periods start. + +nfsd is shut down by a write of 0 to nfsd/threads. All locks and state +are thrown away at that point. + +Between startup and shutdown, the number of threads may be adjusted up +or down by additional writes to nfsd/threads or by writes to +nfsd/pool_threads. + +For more detail about files under nfsd/ and what they control, see +fs/nfsd/nfsctl.c; most of them have detailed comments. + +Implementation notes +^^^^^^^^^^^^^^^^^^^^ + +Note that the rpc server requires the caller to serialize addition and +removal of listening sockets, and startup and shutdown of the server. +For nfsd this is done using nfsd_mutex. diff --git a/Documentation/filesystems/nfs/nfsroot.txt b/Documentation/filesystems/nfs/nfsroot.txt index ffdd9d866ad..2d66ed68812 100644 --- a/Documentation/filesystems/nfs/nfsroot.txt +++ b/Documentation/filesystems/nfs/nfsroot.txt @@ -78,7 +78,8 @@ nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>] flags = hard, nointr, noposix, cto, ac -ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf> +ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>: + <dns0-ip>:<dns1-ip> This parameter tells the kernel how to configure IP addresses of devices and also how to set up the IP routing table. It was originally called @@ -158,6 +159,13 @@ ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf> Default: any + <dns0-ip> IP address of first nameserver. + Value gets exported by /proc/net/pnp which is often linked + on embedded systems by /etc/resolv.conf. + + <dns1-ip> IP address of secound nameserver. + Same as above. + nfsrootdebug diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index fb0a6aeb936..fd8d0d594fc 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -41,6 +41,7 @@ Table of Contents 3.5 /proc/<pid>/mountinfo - Information about mounts 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 3.7 /proc/<pid>/task/<tid>/children - Information about task children + 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file 4 Configuring procfs 4.1 Mount options @@ -142,7 +143,7 @@ Table 1-1: Process specific entries in /proc pagemap Page table stack Report full stack trace, enable via CONFIG_STACKTRACE smaps a extension based on maps, showing the memory consumption of - each mapping + each mapping and flags associated with it .............................................................................. For example, to get the status information of a process, all you have to do is @@ -181,6 +182,7 @@ read the file /proc/PID/status: CapPrm: 0000000000000000 CapEff: 0000000000000000 CapBnd: ffffffffffffffff + Seccomp: 0 voluntary_ctxt_switches: 0 nonvoluntary_ctxt_switches: 1 @@ -237,6 +239,7 @@ Table 1-2: Contents of the status files (as of 2.6.30-rc7) CapPrm bitmap of permitted capabilities CapEff bitmap of effective capabilities CapBnd bitmap of capabilities bounding set + Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...) Cpus_allowed mask of CPUs on which this process may run Cpus_allowed_list Same as previous, but in "list format" Mems_allowed mask of memory nodes allowed to this process @@ -415,8 +418,9 @@ Swap: 0 kB KernelPageSize: 4 kB MMUPageSize: 4 kB Locked: 374 kB +VmFlags: rd ex mr mw me de -The first of these lines shows the same information as is displayed for the +the first of these lines shows the same information as is displayed for the mapping in /proc/PID/maps. The remaining lines show the size of the mapping (size), the amount of the mapping that is currently resident in RAM (RSS), the process' proportional share of this mapping (PSS), the number of clean and @@ -430,6 +434,41 @@ and a page is modified, the file page is replaced by a private anonymous copy. "Swap" shows how much would-be-anonymous memory is also used, but out on swap. +"VmFlags" field deserves a separate description. This member represents the kernel +flags associated with the particular virtual memory area in two letter encoded +manner. The codes are the following: + rd - readable + wr - writeable + ex - executable + sh - shared + mr - may read + mw - may write + me - may execute + ms - may share + gd - stack segment growns down + pf - pure PFN range + dw - disabled write to the mapped file + lo - pages are locked in memory + io - memory mapped I/O area + sr - sequential read advise provided + rr - random read advise provided + dc - do not copy area on fork + de - do not expand area on remapping + ac - area is accountable + nr - swap space is not reserved for the area + ht - area uses huge tlb pages + nl - non-linear mapping + ar - architecture specific flag + dd - do not include area into core dump + mm - mixed map area + hg - huge page advise flag + nh - no-huge page advise flag + mg - mergable advise flag + +Note that there is no guarantee that every flag and associated mnemonic will +be present in all further kernel releases. Things get changed, the flags may +be vanished or the reverse -- new added. + This file is only present if the CONFIG_MMU kernel configuration option is enabled. @@ -1367,16 +1406,10 @@ be used to tune the badness score. Its acceptable values range from -16 (OOM_DISABLE) to disable oom killing entirely for that task. Its value is scaled linearly with /proc/<pid>/oom_score_adj. -Writing to /proc/<pid>/oom_score_adj or /proc/<pid>/oom_adj will change the -other with its scaled value. - The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last value set by a CAP_SYS_RESOURCE process. To reduce the value any lower requires CAP_SYS_RESOURCE. -NOTICE: /proc/<pid>/oom_adj is deprecated and will be removed, please see -Documentation/feature-removal-schedule.txt. - Caveat: when a parent task is selected, the oom killer will sacrifice any first generation children with separate address spaces instead, if possible. This avoids servers and important system daemons from being killed and loses the @@ -1387,7 +1420,7 @@ minimal amount of work. ------------------------------------------------------------- This file can be used to check the current score used by the oom-killer is for -any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which +any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which process should be killed in an out-of-memory situation. @@ -1601,6 +1634,93 @@ pids, so one need to either stop or freeze processes being inspected if precise results are needed. +3.7 /proc/<pid>/fdinfo/<fd> - Information about opened file +--------------------------------------------------------------- +This file provides information associated with an opened file. The regular +files have at least two fields -- 'pos' and 'flags'. The 'pos' represents +the current offset of the opened file in decimal form [see lseek(2) for +details] and 'flags' denotes the octal O_xxx mask the file has been +created with [see open(2) for details]. + +A typical output is + + pos: 0 + flags: 0100002 + +The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags +pair provide additional information particular to the objects they represent. + + Eventfd files + ~~~~~~~~~~~~~ + pos: 0 + flags: 04002 + eventfd-count: 5a + + where 'eventfd-count' is hex value of a counter. + + Signalfd files + ~~~~~~~~~~~~~~ + pos: 0 + flags: 04002 + sigmask: 0000000000000200 + + where 'sigmask' is hex value of the signal mask associated + with a file. + + Epoll files + ~~~~~~~~~~~ + pos: 0 + flags: 02 + tfd: 5 events: 1d data: ffffffffffffffff + + where 'tfd' is a target file descriptor number in decimal form, + 'events' is events mask being watched and the 'data' is data + associated with a target [see epoll(7) for more details]. + + Fsnotify files + ~~~~~~~~~~~~~~ + For inotify files the format is the following + + pos: 0 + flags: 02000000 + inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d + + where 'wd' is a watch descriptor in decimal form, ie a target file + descriptor number, 'ino' and 'sdev' are inode and device where the + target file resides and the 'mask' is the mask of events, all in hex + form [see inotify(7) for more details]. + + If the kernel was built with exportfs support, the path to the target + file is encoded as a file handle. The file handle is provided by three + fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex + format. + + If the kernel is built without exportfs support the file handle won't be + printed out. + + If there is no inotify mark attached yet the 'inotify' line will be omitted. + + For fanotify files the format is + + pos: 0 + flags: 02 + fanotify flags:10 event-flags:0 + fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 + fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 + + where fanotify 'flags' and 'event-flags' are values used in fanotify_init + call, 'mnt_id' is the mount point identifier, 'mflags' is the value of + flags associated with mark which are tracked separately from events + mask. 'ino', 'sdev' are target inode and device, 'mask' is the events + mask and 'ignored_mask' is the mask of events which are to be ignored. + All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask' + does provide information about flags and mask used in fanotify_mark + call [see fsnotify manpage for details]. + + While the first three lines are mandatory and always printed, the rest is + optional and may be omitted if no marks created yet. + + ------------------------------------------------------------------------------ Configuring procfs ------------------------------------------------------------------------------ diff --git a/Documentation/filesystems/vfat.txt b/Documentation/filesystems/vfat.txt index de1e6c4dccf..d230dd9c99b 100644 --- a/Documentation/filesystems/vfat.txt +++ b/Documentation/filesystems/vfat.txt @@ -111,6 +111,15 @@ tz=UTC -- Interpret timestamps as UTC rather than local time. useful when mounting devices (like digital cameras) that are set to UTC in order to avoid the pitfalls of local time. +time_offset=minutes + -- Set offset for conversion of timestamps from local time + used by FAT to UTC. I.e. <minutes> minutes will be subtracted + from each timestamp to convert it to UTC used internally by + Linux. This is useful when time zone set in sys_tz is + not the time zone used by the filesystem. Note that this + option still does not provide correct time stamps in all + cases in presence of DST - time stamps in a different DST + setting will be off by one hour. showexec -- If set, the execute permission bits of the file will be allowed only if the extension part of the name is .EXE, diff --git a/Documentation/filesystems/xfs.txt b/Documentation/filesystems/xfs.txt index 3fc0c31a6f5..3e4b3dd1e04 100644 --- a/Documentation/filesystems/xfs.txt +++ b/Documentation/filesystems/xfs.txt @@ -43,7 +43,7 @@ When mounting an XFS filesystem, the following options are accepted. Issue command to let the block device reclaim space freed by the filesystem. This is useful for SSD devices, thinly provisioned LUNs and virtual machine images, but may have a performance - impact. This option is incompatible with the nodelaylog option. + impact. dmapi Enable the DMAPI (Data Management API) event callouts. @@ -72,8 +72,15 @@ When mounting an XFS filesystem, the following options are accepted. Indicates that XFS is allowed to create inodes at any location in the filesystem, including those which will result in inode numbers occupying more than 32 bits of significance. This is - provided for backwards compatibility, but causes problems for - backup applications that cannot handle large inode numbers. + the default allocation option. Applications which do not handle + inode numbers bigger than 32 bits, should use inode32 option. + + inode32 + Indicates that XFS is limited to create inodes at locations which + will not result in inode numbers with more than 32 bits of + significance. This is provided for backwards compatibility, since + 64 bits inode numbers might cause problems for some applications + that cannot handle large inode numbers. largeio/nolargeio If "nolargeio" is specified, the optimal I/O reported in |