From 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 21 Feb 2023 18:24:12 -0800 Subject: Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next Pull networking updates from Jakub Kicinski: "Core: - Add dedicated kmem_cache for typical/small skb->head, avoid having to access struct page at kfree time, and improve memory use. - Introduce sysctl to set default RPS configuration for new netdevs. - Define Netlink protocol specification format which can be used to describe messages used by each family and auto-generate parsers. Add tools for generating kernel data structures and uAPI headers. - Expose all net/core sysctls inside netns. - Remove 4s sleep in netpoll if carrier is instantly detected on boot. - Add configurable limit of MDB entries per port, and port-vlan. - Continue populating drop reasons throughout the stack. - Retire a handful of legacy Qdiscs and classifiers. Protocols: - Support IPv4 big TCP (TSO frames larger than 64kB). - Add IP_LOCAL_PORT_RANGE socket option, to control local port range on socket by socket basis. - Track and report in procfs number of MPTCP sockets used. - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path manager. - IPv6: don't check net.ipv6.route.max_size and rely on garbage collection to free memory (similarly to IPv4). - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986). - ICMP: add per-rate limit counters. - Add support for user scanning requests in ieee802154. - Remove static WEP support. - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate reporting. - WiFi 7 EHT channel puncturing support (client & AP). BPF: - Add a rbtree data structure following the "next-gen data structure" precedent set by recently added linked list, that is, by using kfunc + kptr instead of adding a new BPF map type. - Expose XDP hints via kfuncs with initial support for RX hash and timestamp metadata. - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to better support decap on GRE tunnel devices not operating in collect metadata. - Improve x86 JIT's codegen for PROBE_MEM runtime error checks. - Remove the need for trace_printk_lock for bpf_trace_printk and bpf_trace_vprintk helpers. - Extend libbpf's bpf_tracing.h support for tracing arguments of kprobes/uprobes and syscall as a special case. - Significantly reduce the search time for module symbols by livepatch and BPF. - Enable cpumasks to be used as kptrs, which is useful for tracing programs tracking which tasks end up running on which CPUs in different time intervals. - Add support for BPF trampoline on s390x and riscv64. - Add capability to export the XDP features supported by the NIC. - Add __bpf_kfunc tag for marking kernel functions as kfuncs. - Add cgroup.memory=nobpf kernel parameter option to disable BPF memory accounting for container environments. Netfilter: - Remove the CLUSTERIP target. It has been marked as obsolete for years, and we still have WARN splats wrt races of the out-of-band /proc interface installed by this target. - Add 'destroy' commands to nf_tables. They are identical to the existing 'delete' commands, but do not return an error if the referenced object (set, chain, rule...) did not exist. Driver API: - Improve cpumask_local_spread() locality to help NICs set the right IRQ affinity on AMD platforms. - Separate C22 and C45 MDIO bus transactions more clearly. - Introduce new DCB table to control DSCP rewrite on egress. - Support configuration of Physical Layer Collision Avoidance (PLCA) Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of shared medium Ethernet. - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing preemption of low priority frames by high priority frames. - Add support for controlling MACSec offload using netlink SET. - Rework devlink instance refcounts to allow registration and de-registration under the instance lock. Split the code into multiple files, drop some of the unnecessarily granular locks and factor out common parts of netlink operation handling. - Add TX frame aggregation parameters (for USB drivers). - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning messages with notifications for debug. - Allow offloading of UDP NEW connections via act_ct. - Add support for per action HW stats in TC. - Support hardware miss to TC action (continue processing in SW from a specific point in the action chain). - Warn if old Wireless Extension user space interface is used with modern cfg80211/mac80211 drivers. Do not support Wireless Extensions for Wi-Fi 7 devices at all. Everyone should switch to using nl80211 interface instead. - Improve the CAN bit timing configuration. Use extack to return error messages directly to user space, update the SJW handling, including the definition of a new default value that will benefit CAN-FD controllers, by increasing their oscillator tolerance. New hardware / drivers: - Ethernet: - nVidia BlueField-3 support (control traffic driver) - Ethernet support for imx93 SoCs - Motorcomm yt8531 gigabit Ethernet PHY - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA) - Microchip LAN8841 PHY (incl. cable diagnostics and PTP) - Amlogic gxl MDIO mux - WiFi: - RealTek RTL8188EU (rtl8xxxu) - Qualcomm Wi-Fi 7 devices (ath12k) - CAN: - Renesas R-Car V4H Drivers: - Bluetooth: - Set Per Platform Antenna Gain (PPAG) for Intel controllers. - Ethernet NICs: - Intel (1G, igc): - support TSN / Qbv / packet scheduling features of i226 model - Intel (100G, ice): - use GNSS subsystem instead of TTY - multi-buffer XDP support - extend support for GPIO pins to E823 devices - nVidia/Mellanox: - update the shared buffer configuration on PFC commands - implement PTP adjphase function for HW offset control - TC support for Geneve and GRE with VF tunnel offload - more efficient crypto key management method - multi-port eswitch support - Netronome/Corigine: - add DCB IEEE support - support IPsec offloading for NFP3800 - Freescale/NXP (enetc): - support XDP_REDIRECT for XDP non-linear buffers - improve reconfig, avoid link flap and waiting for idle - support MAC Merge layer - Other NICs: - sfc/ef100: add basic devlink support for ef100 - ionic: rx_push mode operation (writing descriptors via MMIO) - bnxt: use the auxiliary bus abstraction for RDMA - r8169: disable ASPM and reset bus in case of tx timeout - cpsw: support QSGMII mode for J721e CPSW9G - cpts: support pulse-per-second output - ngbe: add an mdio bus driver - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing - r8152: handle devices with FW with NCM support - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation - virtio-net: support multi buffer XDP - virtio/vsock: replace virtio_vsock_pkt with sk_buff - tsnep: XDP support - Ethernet high-speed switches: - nVidia/Mellanox (mlxsw): - add support for latency TLV (in FW control messages) - Microchip (sparx5): - separate explicit and implicit traffic forwarding rules, make the implicit rules always active - add support for egress DSCP rewrite - IS0 VCAP support (Ingress Classification) - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS etc.) - ES2 VCAP support (Egress Access Control) - support for Per-Stream Filtering and Policing (802.1Q, 8.6.5.1) - Ethernet embedded switches: - Marvell (mv88e6xxx): - add MAB (port auth) offload support - enable PTP receive for mv88e6390 - NXP (ocelot): - support MAC Merge layer - support for the the vsc7512 internal copper phys - Microchip: - lan9303: convert to PHYLINK - lan966x: support TC flower filter statistics - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x - lan937x: support Credit Based Shaper configuration - ksz9477: support Energy Efficient Ethernet - other: - qca8k: convert to regmap read/write API, use bulk operations - rswitch: Improve TX timestamp accuracy - Intel WiFi (iwlwifi): - EHT (Wi-Fi 7) rate reporting - STEP equalizer support: transfer some STEP (connection to radio on platforms with integrated wifi) related parameters from the BIOS to the firmware. - Qualcomm 802.11ax WiFi (ath11k): - IPQ5018 support - Fine Timing Measurement (FTM) responder role support - channel 177 support - MediaTek WiFi (mt76): - per-PHY LED support - mt7996: EHT (Wi-Fi 7) support - Wireless Ethernet Dispatch (WED) reset support - switch to using page pool allocator - RealTek WiFi (rtw89): - support new version of Bluetooth co-existance - Mobile: - rmnet: support TX aggregation" * tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits) page_pool: add a comment explaining the fragment counter usage net: ethtool: fix __ethtool_dev_mm_supported() implementation ethtool: pse-pd: Fix double word in comments xsk: add linux/vmalloc.h to xsk.c sefltests: netdevsim: wait for devlink instance after netns removal selftest: fib_tests: Always cleanup before exit net/mlx5e: Align IPsec ASO result memory to be as required by hardware net/mlx5e: TC, Set CT miss to the specific ct action instance net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG net/mlx5: Refactor tc miss handling to a single function net/mlx5: Kconfig: Make tc offload depend on tc skb extension net/sched: flower: Support hardware miss to tc action net/sched: flower: Move filter handle initialization earlier net/sched: cls_api: Support hardware miss to tc action net/sched: Rename user cookie and act cookie sfc: fix builds without CONFIG_RTC_LIB sfc: clean up some inconsistent indentings net/mlx4_en: Introduce flexible array to silence overflow warning net: lan966x: Fix possible deadlock inside PTP net/ulp: Remove redundant ->clone() test in inet_clone_ulp(). ... --- Documentation/admin-guide/xfs.rst | 543 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 543 insertions(+) create mode 100644 Documentation/admin-guide/xfs.rst (limited to 'Documentation/admin-guide/xfs.rst') diff --git a/Documentation/admin-guide/xfs.rst b/Documentation/admin-guide/xfs.rst new file mode 100644 index 000000000..8de008c0c --- /dev/null +++ b/Documentation/admin-guide/xfs.rst @@ -0,0 +1,543 @@ +.. SPDX-License-Identifier: GPL-2.0 + +====================== +The SGI XFS Filesystem +====================== + +XFS is a high performance journaling filesystem which originated +on the SGI IRIX platform. It is completely multi-threaded, can +support large files and large filesystems, extended attributes, +variable block sizes, is extent based, and makes extensive use of +Btrees (directories, extents, free space) to aid both performance +and scalability. + +Refer to the documentation at https://xfs.wiki.kernel.org/ +for further details. This implementation is on-disk compatible +with the IRIX version of XFS. + + +Mount Options +============= + +When mounting an XFS filesystem, the following options are accepted. + + allocsize=size + Sets the buffered I/O end-of-file preallocation size when + doing delayed allocation writeout (default size is 64KiB). + Valid values for this option are page size (typically 4KiB) + through to 1GiB, inclusive, in power-of-2 increments. + + The default behaviour is for dynamic end-of-file + preallocation size, which uses a set of heuristics to + optimise the preallocation size based on the current + allocation patterns within the file and the access patterns + to the file. Specifying a fixed ``allocsize`` value turns off + the dynamic behaviour. + + attr2 or noattr2 + The options enable/disable an "opportunistic" improvement to + be made in the way inline extended attributes are stored + on-disk. When the new form is used for the first time when + ``attr2`` is selected (either when setting or removing extended + attributes) the on-disk superblock feature bit field will be + updated to reflect this format being in use. + + The default behaviour is determined by the on-disk feature + bit indicating that ``attr2`` behaviour is active. If either + mount option is set, then that becomes the new default used + by the filesystem. + + CRC enabled filesystems always use the ``attr2`` format, and so + will reject the ``noattr2`` mount option if it is set. + + discard or nodiscard (default) + Enable/disable the issuing of commands 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. + + Note: It is currently recommended that you use the ``fstrim`` + application to ``discard`` unused blocks rather than the ``discard`` + mount option because the performance impact of this option + is quite severe. + + grpid/bsdgroups or nogrpid/sysvgroups (default) + These options define what group ID a newly created file + gets. When ``grpid`` is set, it takes the group ID of the + directory in which it is created; otherwise it takes the + ``fsgid`` of the current process, unless the directory has the + ``setgid`` bit set, in which case it takes the ``gid`` from the + parent directory, and also gets the ``setgid`` bit set if it is + a directory itself. + + filestreams + Make the data allocator use the filestreams allocation mode + across the entire filesystem rather than just on directories + configured to use it. + + ikeep or noikeep (default) + When ``ikeep`` is specified, XFS does not delete empty inode + clusters and keeps them around on disk. When ``noikeep`` is + specified, empty inode clusters are returned to the free + space pool. + + inode32 or inode64 (default) + When ``inode32`` is specified, it indicates that XFS limits + inode creation to locations which will not result in inode + numbers with more than 32 bits of significance. + + When ``inode64`` is specified, it 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. + + ``inode32`` is provided for backwards compatibility with older + systems and applications, since 64 bits inode numbers might + cause problems for some applications that cannot handle + large inode numbers. If applications are in use which do + not handle inode numbers bigger than 32 bits, the ``inode32`` + option should be specified. + + largeio or nolargeio (default) + If ``nolargeio`` is specified, the optimal I/O reported in + ``st_blksize`` by **stat(2)** will be as small as possible to allow + user applications to avoid inefficient read/modify/write + I/O. This is typically the page size of the machine, as + this is the granularity of the page cache. + + If ``largeio`` is specified, a filesystem that was created with a + ``swidth`` specified will return the ``swidth`` value (in bytes) + in ``st_blksize``. If the filesystem does not have a ``swidth`` + specified but does specify an ``allocsize`` then ``allocsize`` + (in bytes) will be returned instead. Otherwise the behaviour + is the same as if ``nolargeio`` was specified. + + logbufs=value + Set the number of in-memory log buffers. Valid numbers + range from 2-8 inclusive. + + The default value is 8 buffers. + + If the memory cost of 8 log buffers is too high on small + systems, then it may be reduced at some cost to performance + on metadata intensive workloads. The ``logbsize`` option below + controls the size of each buffer and so is also relevant to + this case. + + logbsize=value + Set the size of each in-memory log buffer. The size may be + specified in bytes, or in kilobytes with a "k" suffix. + Valid sizes for version 1 and version 2 logs are 16384 (16k) + and 32768 (32k). Valid sizes for version 2 logs also + include 65536 (64k), 131072 (128k) and 262144 (256k). The + logbsize must be an integer multiple of the log + stripe unit configured at **mkfs(8)** time. + + The default value for version 1 logs is 32768, while the + default value for version 2 logs is MAX(32768, log_sunit). + + logdev=device and rtdev=device + Use an external log (metadata journal) and/or real-time device. + An XFS filesystem has up to three parts: a data section, a log + section, and a real-time section. The real-time section is + optional, and the log section can be separate from the data + section or contained within it. + + noalign + Data allocations will not be aligned at stripe unit + boundaries. This is only relevant to filesystems created + with non-zero data alignment parameters (``sunit``, ``swidth``) by + **mkfs(8)**. + + norecovery + The filesystem will be mounted without running log recovery. + If the filesystem was not cleanly unmounted, it is likely to + be inconsistent when mounted in ``norecovery`` mode. + Some files or directories may not be accessible because of this. + Filesystems mounted ``norecovery`` must be mounted read-only or + the mount will fail. + + nouuid + Don't check for double mounted file systems using the file + system ``uuid``. This is useful to mount LVM snapshot volumes, + and often used in combination with ``norecovery`` for mounting + read-only snapshots. + + noquota + Forcibly turns off all quota accounting and enforcement + within the filesystem. + + uquota/usrquota/uqnoenforce/quota + User disk quota accounting enabled, and limits (optionally) + enforced. Refer to **xfs_quota(8)** for further details. + + gquota/grpquota/gqnoenforce + Group disk quota accounting enabled and limits (optionally) + enforced. Refer to **xfs_quota(8)** for further details. + + pquota/prjquota/pqnoenforce + Project disk quota accounting enabled and limits (optionally) + enforced. Refer to **xfs_quota(8)** for further details. + + sunit=value and swidth=value + Used to specify the stripe unit and width for a RAID device + or a stripe volume. "value" must be specified in 512-byte + block units. These options are only relevant to filesystems + that were created with non-zero data alignment parameters. + + The ``sunit`` and ``swidth`` parameters specified must be compatible + with the existing filesystem alignment characteristics. In + general, that means the only valid changes to ``sunit`` are + increasing it by a power-of-2 multiple. Valid ``swidth`` values + are any integer multiple of a valid ``sunit`` value. + + Typically the only time these mount options are necessary if + after an underlying RAID device has had it's geometry + modified, such as adding a new disk to a RAID5 lun and + reshaping it. + + swalloc + Data allocations will be rounded up to stripe width boundaries + when the current end of file is being extended and the file + size is larger than the stripe width size. + + wsync + When specified, all filesystem namespace operations are + executed synchronously. This ensures that when the namespace + operation (create, unlink, etc) completes, the change to the + namespace is on stable storage. This is useful in HA setups + where failover must not result in clients seeing + inconsistent namespace presentation during or after a + failover event. + +Deprecation of V4 Format +======================== + +The V4 filesystem format lacks certain features that are supported by +the V5 format, such as metadata checksumming, strengthened metadata +verification, and the ability to store timestamps past the year 2038. +Because of this, the V4 format is deprecated. All users should upgrade +by backing up their files, reformatting, and restoring from the backup. + +Administrators and users can detect a V4 filesystem by running xfs_info +against a filesystem mountpoint and checking for a string containing +"crc=". If no such string is found, please upgrade xfsprogs to the +latest version and try again. + +The deprecation will take place in two parts. Support for mounting V4 +filesystems can now be disabled at kernel build time via Kconfig option. +The option will default to yes until September 2025, at which time it +will be changed to default to no. In September 2030, support will be +removed from the codebase entirely. + +Note: Distributors may choose to withdraw V4 format support earlier than +the dates listed above. + +Deprecated Mount Options +======================== + +=========================== ================ + Name Removal Schedule +=========================== ================ +Mounting with V4 filesystem September 2030 +ikeep/noikeep September 2025 +attr2/noattr2 September 2025 +=========================== ================ + + +Removed Mount Options +===================== + +=========================== ======= + Name Removed +=========================== ======= + delaylog/nodelaylog v4.0 + ihashsize v4.0 + irixsgid v4.0 + osyncisdsync/osyncisosync v4.0 + barrier v4.19 + nobarrier v4.19 +=========================== ======= + +sysctls +======= + +The following sysctls are available for the XFS filesystem: + + fs.xfs.stats_clear (Min: 0 Default: 0 Max: 1) + Setting this to "1" clears accumulated XFS statistics + in /proc/fs/xfs/stat. It then immediately resets to "0". + + fs.xfs.xfssyncd_centisecs (Min: 100 Default: 3000 Max: 720000) + The interval at which the filesystem flushes metadata + out to disk and runs internal cache cleanup routines. + + fs.xfs.filestream_centisecs (Min: 1 Default: 3000 Max: 360000) + The interval at which the filesystem ages filestreams cache + references and returns timed-out AGs back to the free stream + pool. + + fs.xfs.speculative_prealloc_lifetime + (Units: seconds Min: 1 Default: 300 Max: 86400) + The interval at which the background scanning for inodes + with unused speculative preallocation runs. The scan + removes unused preallocation from clean inodes and releases + the unused space back to the free pool. + + fs.xfs.speculative_cow_prealloc_lifetime + This is an alias for speculative_prealloc_lifetime. + + fs.xfs.error_level (Min: 0 Default: 3 Max: 11) + A volume knob for error reporting when internal errors occur. + This will generate detailed messages & backtraces for filesystem + shutdowns, for example. Current threshold values are: + + XFS_ERRLEVEL_OFF: 0 + XFS_ERRLEVEL_LOW: 1 + XFS_ERRLEVEL_HIGH: 5 + + fs.xfs.panic_mask (Min: 0 Default: 0 Max: 256) + Causes certain error conditions to call BUG(). Value is a bitmask; + OR together the tags which represent errors which should cause panics: + + XFS_NO_PTAG 0 + XFS_PTAG_IFLUSH 0x00000001 + XFS_PTAG_LOGRES 0x00000002 + XFS_PTAG_AILDELETE 0x00000004 + XFS_PTAG_ERROR_REPORT 0x00000008 + XFS_PTAG_SHUTDOWN_CORRUPT 0x00000010 + XFS_PTAG_SHUTDOWN_IOERROR 0x00000020 + XFS_PTAG_SHUTDOWN_LOGERROR 0x00000040 + XFS_PTAG_FSBLOCK_ZERO 0x00000080 + XFS_PTAG_VERIFIER_ERROR 0x00000100 + + This option is intended for debugging only. + + fs.xfs.irix_symlink_mode (Min: 0 Default: 0 Max: 1) + Controls whether symlinks are created with mode 0777 (default) + or whether their mode is affected by the umask (irix mode). + + fs.xfs.irix_sgid_inherit (Min: 0 Default: 0 Max: 1) + Controls files created in SGID directories. + If the group ID of the new file does not match the effective group + ID or one of the supplementary group IDs of the parent dir, the + ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl + is set. + + fs.xfs.inherit_sync (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "sync" flag set + by the **xfs_io(8)** chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.inherit_nodump (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "nodump" flag set + by the **xfs_io(8)** chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.inherit_noatime (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "noatime" flag set + by the **xfs_io(8)** chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.inherit_nosymlinks (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "nosymlinks" flag set + by the **xfs_io(8)** chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.inherit_nodefrag (Min: 0 Default: 1 Max: 1) + Setting this to "1" will cause the "nodefrag" flag set + by the **xfs_io(8)** chattr command on a directory to be + inherited by files in that directory. + + fs.xfs.rotorstep (Min: 1 Default: 1 Max: 256) + In "inode32" allocation mode, this option determines how many + files the allocator attempts to allocate in the same allocation + group before moving to the next allocation group. The intent + is to control the rate at which the allocator moves between + allocation groups when allocating extents for new files. + +Deprecated Sysctls +================== + +=========================================== ================ + Name Removal Schedule +=========================================== ================ +fs.xfs.irix_sgid_inherit September 2025 +fs.xfs.irix_symlink_mode September 2025 +fs.xfs.speculative_cow_prealloc_lifetime September 2025 +=========================================== ================ + + +Removed Sysctls +=============== + +============================= ======= + Name Removed +============================= ======= + fs.xfs.xfsbufd_centisec v4.0 + fs.xfs.age_buffer_centisecs v4.0 +============================= ======= + +Error handling +============== + +XFS can act differently according to the type of error found during its +operation. The implementation introduces the following concepts to the error +handler: + + -failure speed: + Defines how fast XFS should propagate an error upwards when a specific + error is found during the filesystem operation. It can propagate + immediately, after a defined number of retries, after a set time period, + or simply retry forever. + + -error classes: + Specifies the subsystem the error configuration will apply to, such as + metadata IO or memory allocation. Different subsystems will have + different error handlers for which behaviour can be configured. + + -error handlers: + Defines the behavior for a specific error. + +The filesystem behavior during an error can be set via ``sysfs`` files. Each +error handler works independently - the first condition met by an error handler +for a specific class will cause the error to be propagated rather than reset and +retried. + +The action taken by the filesystem when the error is propagated is context +dependent - it may cause a shut down in the case of an unrecoverable error, +it may be reported back to userspace, or it may even be ignored because +there's nothing useful we can with the error or anyone we can report it to (e.g. +during unmount). + +The configuration files are organized into the following hierarchy for each +mounted filesystem: + + /sys/fs/xfs//error/// + +Where: + + The short device name of the mounted filesystem. This is the same device + name that shows up in XFS kernel error messages as "XFS(): ..." + + + The subsystem the error configuration belongs to. As of 4.9, the defined + classes are: + + - "metadata": applies metadata buffer write IO + + + The individual error handler configurations. + + +Each filesystem has "global" error configuration options defined in their top +level directory: + + /sys/fs/xfs//error/ + + fail_at_unmount (Min: 0 Default: 1 Max: 1) + Defines the filesystem error behavior at unmount time. + + If set to a value of 1, XFS will override all other error configurations + during unmount and replace them with "immediate fail" characteristics. + i.e. no retries, no retry timeout. This will always allow unmount to + succeed when there are persistent errors present. + + If set to 0, the configured retry behaviour will continue until all + retries and/or timeouts have been exhausted. This will delay unmount + completion when there are persistent errors, and it may prevent the + filesystem from ever unmounting fully in the case of "retry forever" + handler configurations. + + Note: there is no guarantee that fail_at_unmount can be set while an + unmount is in progress. It is possible that the ``sysfs`` entries are + removed by the unmounting filesystem before a "retry forever" error + handler configuration causes unmount to hang, and hence the filesystem + must be configured appropriately before unmount begins to prevent + unmount hangs. + +Each filesystem has specific error class handlers that define the error +propagation behaviour for specific errors. There is also a "default" error +handler defined, which defines the behaviour for all errors that don't have +specific handlers defined. Where multiple retry constraints are configured for +a single error, the first retry configuration that expires will cause the error +to be propagated. The handler configurations are found in the directory: + + /sys/fs/xfs//error/// + + max_retries (Min: -1 Default: Varies Max: INTMAX) + Defines the allowed number of retries of a specific error before + the filesystem will propagate the error. The retry count for a given + error context (e.g. a specific metadata buffer) is reset every time + there is a successful completion of the operation. + + Setting the value to "-1" will cause XFS to retry forever for this + specific error. + + Setting the value to "0" will cause XFS to fail immediately when the + specific error is reported. + + Setting the value to "N" (where 0 < N < Max) will make XFS retry the + operation "N" times before propagating the error. + + retry_timeout_seconds (Min: -1 Default: Varies Max: 1 day) + Define the amount of time (in seconds) that the filesystem is + allowed to retry its operations when the specific error is + found. + + Setting the value to "-1" will allow XFS to retry forever for this + specific error. + + Setting the value to "0" will cause XFS to fail immediately when the + specific error is reported. + + Setting the value to "N" (where 0 < N < Max) will allow XFS to retry the + operation for up to "N" seconds before propagating the error. + +**Note:** The default behaviour for a specific error handler is dependent on both +the class and error context. For example, the default values for +"metadata/ENODEV" are "0" rather than "-1" so that this error handler defaults +to "fail immediately" behaviour. This is done because ENODEV is a fatal, +unrecoverable error no matter how many times the metadata IO is retried. + +Workqueue Concurrency +===================== + +XFS uses kernel workqueues to parallelize metadata update processes. This +enables it to take advantage of storage hardware that can service many IO +operations simultaneously. This interface exposes internal implementation +details of XFS, and as such is explicitly not part of any userspace API/ABI +guarantee the kernel may give userspace. These are undocumented features of +the generic workqueue implementation XFS uses for concurrency, and they are +provided here purely for diagnostic and tuning purposes and may change at any +time in the future. + +The control knobs for a filesystem's workqueues are organized by task at hand +and the short name of the data device. They all can be found in: + + /sys/bus/workqueue/devices/${task}!${device} + +================ =========== + Task Description +================ =========== + xfs_iwalk-$pid Inode scans of the entire filesystem. Currently limited to + mount time quotacheck. + xfs-gc Background garbage collection of disk space that have been + speculatively allocated beyond EOF or for staging copy on + write operations. +================ =========== + +For example, the knobs for the quotacheck workqueue for /dev/nvme0n1 would be +found in /sys/bus/workqueue/devices/xfs_iwalk-1111!nvme0n1/. + +The interesting knobs for XFS workqueues are as follows: + +============ =========== + Knob Description +============ =========== + max_active Maximum number of background threads that can be started to + run the work. + cpumask CPUs upon which the threads are allowed to run. + nice Relative priority of scheduling the threads. These are the + same nice levels that can be applied to userspace processes. +============ =========== -- cgit v1.2.3