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author | 2023-02-21 18:24:12 -0800 | |
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committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /fs/jffs2/README.Locking | |
download | linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip |
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
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().
...
Diffstat (limited to 'fs/jffs2/README.Locking')
-rw-r--r-- | fs/jffs2/README.Locking | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/fs/jffs2/README.Locking b/fs/jffs2/README.Locking new file mode 100644 index 000000000..8918ac905 --- /dev/null +++ b/fs/jffs2/README.Locking @@ -0,0 +1,169 @@ + + JFFS2 LOCKING DOCUMENTATION + --------------------------- + +This document attempts to describe the existing locking rules for +JFFS2. It is not expected to remain perfectly up to date, but ought to +be fairly close. + + + alloc_sem + --------- + +The alloc_sem is a per-filesystem mutex, used primarily to ensure +contiguous allocation of space on the medium. It is automatically +obtained during space allocations (jffs2_reserve_space()) and freed +upon write completion (jffs2_complete_reservation()). Note that +the garbage collector will obtain this right at the beginning of +jffs2_garbage_collect_pass() and release it at the end, thereby +preventing any other write activity on the file system during a +garbage collect pass. + +When writing new nodes, the alloc_sem must be held until the new nodes +have been properly linked into the data structures for the inode to +which they belong. This is for the benefit of NAND flash - adding new +nodes to an inode may obsolete old ones, and by holding the alloc_sem +until this happens we ensure that any data in the write-buffer at the +time this happens are part of the new node, not just something that +was written afterwards. Hence, we can ensure the newly-obsoleted nodes +don't actually get erased until the write-buffer has been flushed to +the medium. + +With the introduction of NAND flash support and the write-buffer, +the alloc_sem is also used to protect the wbuf-related members of the +jffs2_sb_info structure. Atomically reading the wbuf_len member to see +if the wbuf is currently holding any data is permitted, though. + +Ordering constraints: See f->sem. + + + File Mutex f->sem + --------------------- + +This is the JFFS2-internal equivalent of the inode mutex i->i_sem. +It protects the contents of the jffs2_inode_info private inode data, +including the linked list of node fragments (but see the notes below on +erase_completion_lock), etc. + +The reason that the i_sem itself isn't used for this purpose is to +avoid deadlocks with garbage collection -- the VFS will lock the i_sem +before calling a function which may need to allocate space. The +allocation may trigger garbage-collection, which may need to move a +node belonging to the inode which was locked in the first place by the +VFS. If the garbage collection code were to attempt to lock the i_sem +of the inode from which it's garbage-collecting a physical node, this +lead to deadlock, unless we played games with unlocking the i_sem +before calling the space allocation functions. + +Instead of playing such games, we just have an extra internal +mutex, which is obtained by the garbage collection code and also +by the normal file system code _after_ allocation of space. + +Ordering constraints: + + 1. Never attempt to allocate space or lock alloc_sem with + any f->sem held. + 2. Never attempt to lock two file mutexes in one thread. + No ordering rules have been made for doing so. + 3. Never lock a page cache page with f->sem held. + + + erase_completion_lock spinlock + ------------------------------ + +This is used to serialise access to the eraseblock lists, to the +per-eraseblock lists of physical jffs2_raw_node_ref structures, and +(NB) the per-inode list of physical nodes. The latter is a special +case - see below. + +As the MTD API no longer permits erase-completion callback functions +to be called from bottom-half (timer) context (on the basis that nobody +ever actually implemented such a thing), it's now sufficient to use +a simple spin_lock() rather than spin_lock_bh(). + +Note that the per-inode list of physical nodes (f->nodes) is a special +case. Any changes to _valid_ nodes (i.e. ->flash_offset & 1 == 0) in +the list are protected by the file mutex f->sem. But the erase code +may remove _obsolete_ nodes from the list while holding only the +erase_completion_lock. So you can walk the list only while holding the +erase_completion_lock, and can drop the lock temporarily mid-walk as +long as the pointer you're holding is to a _valid_ node, not an +obsolete one. + +The erase_completion_lock is also used to protect the c->gc_task +pointer when the garbage collection thread exits. The code to kill the +GC thread locks it, sends the signal, then unlocks it - while the GC +thread itself locks it, zeroes c->gc_task, then unlocks on the exit path. + + + inocache_lock spinlock + ---------------------- + +This spinlock protects the hashed list (c->inocache_list) of the +in-core jffs2_inode_cache objects (each inode in JFFS2 has the +correspondent jffs2_inode_cache object). So, the inocache_lock +has to be locked while walking the c->inocache_list hash buckets. + +This spinlock also covers allocation of new inode numbers, which is +currently just '++->highest_ino++', but might one day get more complicated +if we need to deal with wrapping after 4 milliard inode numbers are used. + +Note, the f->sem guarantees that the correspondent jffs2_inode_cache +will not be removed. So, it is allowed to access it without locking +the inocache_lock spinlock. + +Ordering constraints: + + If both erase_completion_lock and inocache_lock are needed, the + c->erase_completion has to be acquired first. + + + erase_free_sem + -------------- + +This mutex is only used by the erase code which frees obsolete node +references and the jffs2_garbage_collect_deletion_dirent() function. +The latter function on NAND flash must read _obsolete_ nodes to +determine whether the 'deletion dirent' under consideration can be +discarded or whether it is still required to show that an inode has +been unlinked. Because reading from the flash may sleep, the +erase_completion_lock cannot be held, so an alternative, more +heavyweight lock was required to prevent the erase code from freeing +the jffs2_raw_node_ref structures in question while the garbage +collection code is looking at them. + +Suggestions for alternative solutions to this problem would be welcomed. + + + wbuf_sem + -------- + +This read/write semaphore protects against concurrent access to the +write-behind buffer ('wbuf') used for flash chips where we must write +in blocks. It protects both the contents of the wbuf and the metadata +which indicates which flash region (if any) is currently covered by +the buffer. + +Ordering constraints: + Lock wbuf_sem last, after the alloc_sem or and f->sem. + + + c->xattr_sem + ------------ + +This read/write semaphore protects against concurrent access to the +xattr related objects which include stuff in superblock and ic->xref. +In read-only path, write-semaphore is too much exclusion. It's enough +by read-semaphore. But you must hold write-semaphore when updating, +creating or deleting any xattr related object. + +Once xattr_sem released, there would be no assurance for the existence +of those objects. Thus, a series of processes is often required to retry, +when updating such a object is necessary under holding read semaphore. +For example, do_jffs2_getxattr() holds read-semaphore to scan xref and +xdatum at first. But it retries this process with holding write-semaphore +after release read-semaphore, if it's necessary to load name/value pair +from medium. + +Ordering constraints: + Lock xattr_sem last, after the alloc_sem. |