Questions about the openwrt file system overlay, jffs2, ubifs, ext4

Hello everyone, I recently encountered a problem with the file system on openwrt. I hope someone can help me.

Question 1: When using emmc, the overlay file system mounted in jffs2 format has exceeded 3G bytes. Is there any problem with this? Because when I look at the description of the jffs2 file system, the maximum file system is 128M bytes.

I tested writing a file of 1000M bytes, but the file system only consumed about 30M bytes, as shown in the figure:

Question 2. Should I use rootfstype = squashfs, ext4? But I changed the kernel startup command line parameter to rootfstype = squashfs, ext4, use squashfs.combined.bin,but the system does not recognize the file system

By the way, I have successfully run the board of nand flash, and I am currently testing the board of flash for emmc.

When using imx6, I have used the latest branch of openwrt to verify that the overlay supports rootfstype = squashfs, ubifs.here is logs:

[    1.358530] Creating 5 MTD partitions on "gpmi-nand":
[    1.363689] 0x000000000000-0x000000400000 : "uboot"
[    1.381474] 0x000000400000-0x000000e00000 : "kernel"
[    1.399690] 0x000000e00000-0x000000f00000 : "dtb"
[    1.417313] 0x000000f00000-0x000002d00000 : "backup"
[    1.436103] 0x000002d00000-0x000010000000 : "ubi"
[    1.460574] gpmi-nand 1806000.gpmi-nand: driver registered.
[    1.472067] spi_imx 2008000.ecspi: probed
[    1.479211] spi_imx 200c000.ecspi: probed
[    1.485365] libphy: Fixed MDIO Bus: probed
[    1.491093] CAN device driver interface
[    1.495671] 2090000.can supply xceiver not found, using dummy regulator
[    1.505047] flexcan 2090000.can: device registered (reg_base=90a7c000, irq=28)
[    1.512631] 2094000.can supply xceiver not found, using dummy regulator
[    1.521722] flexcan 2094000.can: device registered (reg_base=90a84000, irq=29)
[    1.532385] 20b4000.ethernet supply phy not found, using dummy regulator
[    1.540289] pps pps0: new PPS source ptp0
[    1.544775] fec 20b4000.ethernet eth1 (uninitialized): Invalid MAC address: 00:00:00:00:00:00
[    1.553372] fec 20b4000.ethernet eth1 (uninitialized): Using random MAC address: ea:c9:dc:cd:9a:83
[    1.563414] libphy: fec_enet_mii_bus: probed
[    1.582302] fec 20b4000.ethernet eth1: registered PHC device 0
[    1.590469] 2188000.ethernet supply phy not found, using dummy regulator
[    1.598425] pps pps1: new PPS source ptp1
[    1.605563] fec 2188000.ethernet eth0: registered PHC device 1
[    1.613492] usbcore: registered new interface driver rtl8188eu
[    1.619842] usbcore: registered new interface driver asix
[    1.625602] usbcore: registered new interface driver ax88179_178a
[    1.631907] usbcore: registered new interface driver cdc_ether
[    1.638048] usbcore: registered new interface driver smsc95xx
[    1.644038] usbcore: registered new interface driver net1080
[    1.649858] usbcore: registered new interface driver cdc_subset
[    1.656003] usbcore: registered new interface driver zaurus
[    1.661786] usbcore: registered new interface driver cdc_ncm
[    1.667674] usbcore: registered new interface driver huawei_cdc_ncm
[    1.674039] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
[    1.680603] ehci-pci: EHCI PCI platform driver
[    1.685289] ehci-mxc: Freescale On-Chip EHCI Host driver
[    1.691280] usbcore: registered new interface driver cdc_wdm
[    1.697407] usbcore: registered new interface driver usb-storage
[    1.703849] usbcore: registered new interface driver usbserial
[    1.709829] usbcore: registered new interface driver usbserial_generic
[    1.716713] usbserial: USB Serial support registered for generic
[    1.722884] usbcore: registered new interface driver ftdi_sio
[    1.728866] usbserial: USB Serial support registered for FTDI USB Serial Device
[    1.736393] usbcore: registered new interface driver option
[    1.742100] usbserial: USB Serial support registered for GSM modem (1-port)
[    1.749270] usbcore: registered new interface driver pl2303
[    1.755041] usbserial: USB Serial support registered for pl2303
[    1.761134] usbcore: registered new interface driver usb_ehset_test
[    1.770557] 2184800.usbmisc supply vbus-wakeup not found, using dummy regulator
[    1.780285] 2184000.usb supply vbus not found, using dummy regulator
[    1.804448] 2184200.usb supply vbus not found, using dummy regulator
[    1.814839] ci_hdrc ci_hdrc.1: EHCI Host Controller
[    1.819837] ci_hdrc ci_hdrc.1: new USB bus registered, assigned bus number 1
[    1.853735] ci_hdrc ci_hdrc.1: USB 2.0 started, EHCI 1.00
[    1.861112] hub 1-0:1.0: USB hub found
[    1.865130] hub 1-0:1.0: 1 port detected
[    1.871856] mousedev: PS/2 mouse device common for all mice
[    1.879771] input: 20cc000.snvs:snvs-powerkey as /devices/soc0/soc/2000000.aips-bus/20cc000.snvs/20cc000.snvs:snvs-powerkey/input/input0
[    1.898422] snvs_rtc 20cc000.snvs:snvs-rtc-lp: rtc core: registered 20cc000.snvs:snvs-r as rtc0
[    1.908098] i2c /dev entries driver
[    1.912610] IR NEC protocol handler initialized
[    1.917297] IR RC5(x/sz) protocol handler initialized
[    1.922388] IR RC6 protocol handler initialized
[    1.927003] IR JVC protocol handler initialized
[    1.931571] IR Sony protocol handler initialized
[    1.936266] IR SANYO protocol handler initialized
[    1.941004] IR Sharp protocol handler initialized
[    1.945785] IR MCE Keyboard/mouse protocol handler initialized
[    1.951651] IR XMP protocol handler initialized
[    1.959127] pxp-v4l2 pxp_v4l2: initialized
[    1.968249] imx2-wdt 20bc000.wdog: timeout 60 sec (nowayout=0)
[    1.975435] Bluetooth: HCI UART driver ver 2.3
[    1.979945] Bluetooth: HCI UART protocol H4 registered
[    1.985234] Bluetooth: HCI UART protocol BCSP registered
[    1.990588] Bluetooth: HCI UART protocol ATH3K registered
[    1.996307] usbcore: registered new interface driver bcm203x
[    2.002200] usbcore: registered new interface driver btusb
[    2.007991] usbcore: registered new interface driver ath3k
[    2.015776] sdhci: Secure Digital Host Controller Interface driver
[    2.022014] sdhci: Copyright(c) Pierre Ossman
[    2.026517] sdhci-pltfm: SDHCI platform and OF driver helper
[    2.034572] sdhci-esdhc-imx 2190000.usdhc: could not get ultra high speed state, work on normal mode
[    2.103704] mmc0: SDHCI controller on 2190000.usdhc [2190000.usdhc] using ADMA
[    2.125689] random: fast init done
[    2.139740] usbcore: registered new interface driver usbhid
[    2.145729] usbhid: USB HID core driver
[    2.152039] 2198000.adc supply vref not found, using dummy regulator
[    2.185147] NET: Registered protocol family 26
[    2.191285] NET: Registered protocol family 10
[    2.208969] sit: IPv6, IPv4 and MPLS over IPv4 tunneling driver
[    2.219763] NET: Registered protocol family 17
[    2.224589] usb 1-1: new high-speed USB device number 2 using ci_hdrc
[    2.231569] can: controller area network core (rev 20120528 abi 9)
[    2.238791] NET: Registered protocol family 29
[    2.244536] can: raw protocol (rev 20120528)
[    2.250071] can: broadcast manager protocol (rev 20161123 t)
[    2.255919] can: netlink gateway (rev 20130117) max_hops=1
[    2.262083] Bluetooth: RFCOMM TTY layer initialized
[    2.267194] Bluetooth: RFCOMM socket layer initialized
[    2.272418] Bluetooth: RFCOMM ver 1.11
[    2.276394] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[    2.281750] Bluetooth: BNEP filters: protocol multicast
[    2.289272] Bluetooth: BNEP socket layer initialized
[    2.294556] Bluetooth: HIDP (Human Interface Emulation) ver 1.2
[    2.300543] Bluetooth: HIDP socket layer initialized
[    2.305756] 8021q: 802.1Q VLAN Support v1.8
[    2.310106] Key type dns_resolver registered
[    2.324731] cpu cpu0: Registered imx6q-cpufreq
[    2.393531] imx_thermal 2000000.aips-bus:tempmon: Industrial CPU temperature grade - max:105C critical:100C passive:95C
[    2.405405] ubi0: default fastmap pool size: 80
[    2.410234] ubi0: default fastmap WL pool size: 40
[    2.417433] ubi0: attaching mtd4
[    2.425315] hub 1-1:1.0: USB hub found
[    2.430312] hub 1-1:1.0: 4 ports detected
[    2.753680] usb 1-1.2: new high-speed USB device number 3 using ci_hdrc
[    4.423456] random: crng init done
[    4.522157] ubi0: scanning is finished
[    4.545907] ubi0: attached mtd4 (name "ubi", size 211 MiB)
[    4.551444] ubi0: PEB size: 131072 bytes (128 KiB), LEB size: 126976 bytes
[    4.558473] ubi0: min./max. I/O unit sizes: 2048/2048, sub-page size 2048
[    4.565337] ubi0: VID header offset: 2048 (aligned 2048), data offset: 4096
[    4.572325] ubi0: good PEBs: 1684, bad PEBs: 4, corrupted PEBs: 0
[    4.578499] ubi0: user volume: 2, internal volumes: 1, max. volumes count: 128
[    4.585789] ubi0: max/mean erase counter: 4/1, WL threshold: 4096, image sequence number: 1479956245
[    4.595163] ubi0: available PEBs: 0, total reserved PEBs: 1684, PEBs reserved for bad PEB handling: 36
[    4.604582] ubi0: background thread "ubi_bgt0d" started, PID 97
[    4.622703] mtd: device 5 (rootfs) set to be root filesystem
[    4.653811] block ubiblock0_0: created from ubi0:0(rootfs)
[    4.659414] snvs_rtc 20cc000.snvs:snvs-rtc-lp: setting system clock to 1970-01-01 00:00:02 UTC (2)
[    4.669251] ALSA device list:
[    4.672253]   No soundcards found.
[    4.684842] VFS: Mounted root (squashfs filesystem) readonly on device 254:0.
[    4.694458] Freeing unused kernel memory: 1024K
[    5.952310] init: Console is alive
[    5.956426] init: - watchdog -
[    6.884666] kmodloader: loading kernel modules from /etc/modules-boot.d/*
[    6.968703] gpio_button_hotplug: loading out-of-tree module taints kernel.
[    6.980827] ehci-platform: EHCI generic platform driver
[    6.991481] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
[    7.009594] init: - preinit -
[    8.743994] SMSC LAN8710/LAN8720 20b4000.ethernet-1:00: attached PHY driver [SMSC LAN8710/LAN8720] (mii_bus:phy_addr=20b4000.ethernet-1:00, irq=-1)
[    8.757727] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[   12.236463] mount_root: loading kmods from internal overlay
[   12.290281] kmodloader: loading kernel modules from //etc/modules-boot.d/*
[   12.303139] kmodloader: done loading kernel modules from //etc/modules-boot.d/*
[   12.480005] blk_update_request: I/O error, dev mtdblock0, sector 0
[   12.491117] blk_update_request: I/O error, dev mtdblock0, sector 0
[   12.497334] Buffer I/O error on dev mtdblock0, logical block 0, async page read
[   12.639636] UBIFS (ubi0:1): background thread "ubifs_bgt0_1" started, PID 146
[   12.724932] UBIFS (ubi0:1): recovery needed
[   13.110324] UBIFS (ubi0:1): recovery completed
[   13.115110] UBIFS (ubi0:1): UBIFS: mounted UBI device 0, volume 1, name "rootfs_data"
[   13.123440] UBIFS (ubi0:1): LEB size: 126976 bytes (124 KiB), min./max. I/O unit sizes: 2048 bytes/2048 bytes
[   13.133557] UBIFS (ubi0:1): FS size: 163672064 bytes (156 MiB, 1289 LEBs), journal size 8253440 bytes (7 MiB, 65 LEBs)
[   13.144329] UBIFS (ubi0:1): reserved for root: 4952683 bytes (4836 KiB)
[   13.150970] UBIFS (ubi0:1): media format: w4/r0 (latest is w4/r0), UUID 190733BA-FF82-493C-B732-332B384253C4, small LPT model
[   13.164384] UBIFS (ubi0:1): full atime support is enabled.
[   13.170220] block: attempting to load /tmp/ubifs_cfg/upper/etc/config/fstab
[   13.186836] block: extroot: not configured
[   13.226008] UBIFS (ubi0:1): un-mount UBI device 0
[   13.230780] UBIFS (ubi0:1): background thread "ubifs_bgt0_1" stops
[   13.249707] UBIFS (ubi0:1): background thread "ubifs_bgt0_1" started, PID 147
[   13.418793] UBIFS (ubi0:1): UBIFS: mounted UBI device 0, volume 1, name "rootfs_data"
[   13.426759] UBIFS (ubi0:1): LEB size: 126976 bytes (124 KiB), min./max. I/O unit sizes: 2048 bytes/2048 bytes
[   13.436757] UBIFS (ubi0:1): FS size: 163672064 bytes (156 MiB, 1289 LEBs), journal size 8253440 bytes (7 MiB, 65 LEBs)
[   13.447513] UBIFS (ubi0:1): reserved for root: 4952683 bytes (4836 KiB)
[   13.454188] UBIFS (ubi0:1): media format: w4/r0 (latest is w4/r0), UUID 190733BA-FF82-493C-B732-332B384253C4, small LPT model
[   13.468865] UBIFS (ubi0:1): full atime support is enabled.
[   13.491164] blk_update_request: I/O error, dev mtdblock0, sector 0
[   13.502288] blk_update_request: I/O error, dev mtdblock0, sector 0
[   13.508506] Buffer I/O error on dev mtdblock0, logical block 0, async page read
[   13.610149] ubi0 error: ubi_open_volume.part.0: cannot open device 0, volume 1, error -16
[   13.638225] block: attempting to load /tmp/ubifs_cfg/upper/etc/config/fstab
[   13.654566] block: extroot: not configured
[   13.688114] mount_root: switching to ubifs overlay
[   13.750669] urandom-seed: Seeding with /etc/urandom.seed
[   13.917238] procd: - early -
[   13.920346] procd: - watchdog -
[   15.069737] procd: - watchdog -
[   15.073401] procd: - ubus -
[   15.328278] procd: - init -