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authorLibravatar Linus Torvalds <torvalds@linux-foundation.org>2023-02-21 18:24:12 -0800
committerLibravatar Linus Torvalds <torvalds@linux-foundation.org>2023-02-21 18:24:12 -0800
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treecc5c2d0a898769fd59549594fedb3ee6f84e59a0 /fs/cramfs/README
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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(). ...
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+Notes on Filesystem Layout
+--------------------------
+
+These notes describe what mkcramfs generates. Kernel requirements are
+a bit looser, e.g. it doesn't care if the <file_data> items are
+swapped around (though it does care that directory entries (inodes) in
+a given directory are contiguous, as this is used by readdir).
+
+All data is currently in host-endian format; neither mkcramfs nor the
+kernel ever do swabbing. (See section `Block Size' below.)
+
+<filesystem>:
+ <superblock>
+ <directory_structure>
+ <data>
+
+<superblock>: struct cramfs_super (see cramfs_fs.h).
+
+<directory_structure>:
+ For each file:
+ struct cramfs_inode (see cramfs_fs.h).
+ Filename. Not generally null-terminated, but it is
+ null-padded to a multiple of 4 bytes.
+
+The order of inode traversal is described as "width-first" (not to be
+confused with breadth-first); i.e. like depth-first but listing all of
+a directory's entries before recursing down its subdirectories: the
+same order as `ls -AUR' (but without the /^\..*:$/ directory header
+lines); put another way, the same order as `find -type d -exec
+ls -AU1 {} \;'.
+
+Beginning in 2.4.7, directory entries are sorted. This optimization
+allows cramfs_lookup to return more quickly when a filename does not
+exist, speeds up user-space directory sorts, etc.
+
+<data>:
+ One <file_data> for each file that's either a symlink or a
+ regular file of non-zero st_size.
+
+<file_data>:
+ nblocks * <block_pointer>
+ (where nblocks = (st_size - 1) / blksize + 1)
+ nblocks * <block>
+ padding to multiple of 4 bytes
+
+The i'th <block_pointer> for a file stores the byte offset of the
+*end* of the i'th <block> (i.e. one past the last byte, which is the
+same as the start of the (i+1)'th <block> if there is one). The first
+<block> immediately follows the last <block_pointer> for the file.
+<block_pointer>s are each 32 bits long.
+
+When the CRAMFS_FLAG_EXT_BLOCK_POINTERS capability bit is set, each
+<block_pointer>'s top bits may contain special flags as follows:
+
+CRAMFS_BLK_FLAG_UNCOMPRESSED (bit 31):
+ The block data is not compressed and should be copied verbatim.
+
+CRAMFS_BLK_FLAG_DIRECT_PTR (bit 30):
+ The <block_pointer> stores the actual block start offset and not
+ its end, shifted right by 2 bits. The block must therefore be
+ aligned to a 4-byte boundary. The block size is either blksize
+ if CRAMFS_BLK_FLAG_UNCOMPRESSED is also specified, otherwise
+ the compressed data length is included in the first 2 bytes of
+ the block data. This is used to allow discontiguous data layout
+ and specific data block alignments e.g. for XIP applications.
+
+
+The order of <file_data>'s is a depth-first descent of the directory
+tree, i.e. the same order as `find -size +0 \( -type f -o -type l \)
+-print'.
+
+
+<block>: The i'th <block> is the output of zlib's compress function
+applied to the i'th blksize-sized chunk of the input data if the
+corresponding CRAMFS_BLK_FLAG_UNCOMPRESSED <block_ptr> bit is not set,
+otherwise it is the input data directly.
+(For the last <block> of the file, the input may of course be smaller.)
+Each <block> may be a different size. (See <block_pointer> above.)
+
+<block>s are merely byte-aligned, not generally u32-aligned.
+
+When CRAMFS_BLK_FLAG_DIRECT_PTR is specified then the corresponding
+<block> may be located anywhere and not necessarily contiguous with
+the previous/next blocks. In that case it is minimally u32-aligned.
+If CRAMFS_BLK_FLAG_UNCOMPRESSED is also specified then the size is always
+blksize except for the last block which is limited by the file length.
+If CRAMFS_BLK_FLAG_DIRECT_PTR is set and CRAMFS_BLK_FLAG_UNCOMPRESSED
+is not set then the first 2 bytes of the block contains the size of the
+remaining block data as this cannot be determined from the placement of
+logically adjacent blocks.
+
+
+Holes
+-----
+
+This kernel supports cramfs holes (i.e. [efficient representation of]
+blocks in uncompressed data consisting entirely of NUL bytes), but by
+default mkcramfs doesn't test for & create holes, since cramfs in
+kernels up to at least 2.3.39 didn't support holes. Run mkcramfs
+with -z if you want it to create files that can have holes in them.
+
+
+Tools
+-----
+
+The cramfs user-space tools, including mkcramfs and cramfsck, are
+located at <http://sourceforge.net/projects/cramfs/>.
+
+
+Future Development
+==================
+
+Block Size
+----------
+
+(Block size in cramfs refers to the size of input data that is
+compressed at a time. It's intended to be somewhere around
+PAGE_SIZE for cramfs_read_folio's convenience.)
+
+The superblock ought to indicate the block size that the fs was
+written for, since comments in <linux/pagemap.h> indicate that
+PAGE_SIZE may grow in future (if I interpret the comment
+correctly).
+
+Currently, mkcramfs #define's PAGE_SIZE as 4096 and uses that
+for blksize, whereas Linux-2.3.39 uses its PAGE_SIZE, which in
+turn is defined as PAGE_SIZE (which can be as large as 32KB on arm).
+This discrepancy is a bug, though it's not clear which should be
+changed.
+
+One option is to change mkcramfs to take its PAGE_SIZE from
+<asm/page.h>. Personally I don't like this option, but it does
+require the least amount of change: just change `#define
+PAGE_SIZE (4096)' to `#include <asm/page.h>'. The disadvantage
+is that the generated cramfs cannot always be shared between different
+kernels, not even necessarily kernels of the same architecture if
+PAGE_SIZE is subject to change between kernel versions
+(currently possible with arm and ia64).
+
+The remaining options try to make cramfs more sharable.
+
+One part of that is addressing endianness. The two options here are
+`always use little-endian' (like ext2fs) or `writer chooses
+endianness; kernel adapts at runtime'. Little-endian wins because of
+code simplicity and little CPU overhead even on big-endian machines.
+
+The cost of swabbing is changing the code to use the le32_to_cpu
+etc. macros as used by ext2fs. We don't need to swab the compressed
+data, only the superblock, inodes and block pointers.
+
+
+The other part of making cramfs more sharable is choosing a block
+size. The options are:
+
+ 1. Always 4096 bytes.
+
+ 2. Writer chooses blocksize; kernel adapts but rejects blocksize >
+ PAGE_SIZE.
+
+ 3. Writer chooses blocksize; kernel adapts even to blocksize >
+ PAGE_SIZE.
+
+It's easy enough to change the kernel to use a smaller value than
+PAGE_SIZE: just make cramfs_read_folio read multiple blocks.
+
+The cost of option 1 is that kernels with a larger PAGE_SIZE
+value don't get as good compression as they can.
+
+The cost of option 2 relative to option 1 is that the code uses
+variables instead of #define'd constants. The gain is that people
+with kernels having larger PAGE_SIZE can make use of that if
+they don't mind their cramfs being inaccessible to kernels with
+smaller PAGE_SIZE values.
+
+Option 3 is easy to implement if we don't mind being CPU-inefficient:
+e.g. get read_folio to decompress to a buffer of size MAX_BLKSIZE (which
+must be no larger than 32KB) and discard what it doesn't need.
+Getting read_folio to read into all the covered pages is harder.
+
+The main advantage of option 3 over 1, 2, is better compression. The
+cost is greater complexity. Probably not worth it, but I hope someone
+will disagree. (If it is implemented, then I'll re-use that code in
+e2compr.)
+
+
+Another cost of 2 and 3 over 1 is making mkcramfs use a different
+block size, but that just means adding and parsing a -b option.
+
+
+Inode Size
+----------
+
+Given that cramfs will probably be used for CDs etc. as well as just
+silicon ROMs, it might make sense to expand the inode a little from
+its current 12 bytes. Inodes other than the root inode are followed
+by filename, so the expansion doesn't even have to be a multiple of 4
+bytes.