- kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

list of all subsystems (swap space)
by inventsekar Jan. 20, 2018

Jan. 20, 2018

Hi All, 1. so I tried to find out which subsystem the swap space comes under.. when I googled for list of subsystems Linux architecture, no luck. Between, I found out that kernel map ( http://www.makelinux.net/kernel_map/ ), which gives me kind of subsystems/modules. Is there any documentation/links for list of subsystems on Linux?!?! 2. it looks like swap space itself a separate subsystem/module. I thought to subscribe to some lkml dl for swap, but I am not finding any DL at all. Please suggest. Best regards Sekar On Jan 15, 2018 11:52 PM, "inventsekar" <inventsekar(a)gmail.com> wrote: Hi All, I have been reading about swap space and got these questions... 1. Btrfs was the only one fs which got this below issue or any other fs also? 2. The other way around - is there any FS which is best suitable (best performance) for swap file? 2. Is this issue still there or the wiki isn't updated? *https://wiki.archlinux.org/index.php/swap <https://wiki.archlinux.org/index.php/swap>* *Warning:* Btrfs <https://wiki.archlinux.org/index.php/Btrfs> does not support swap files. Failure to heed this warning may result in file system corruption. While a swap file may be used on Btrfs when mounted through a loop device, this will result in severely degraded swap performance. Any suggestions, links, documentations please. Best regards Sekar

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About File systems magic numbers
by inventsekar Jan. 18, 2018

Jan. 18, 2018

Hi All, i have been reading Unix filesystem - evolution, design and implementation by Steve D. Pate and it provides a simple file system source code for learning and playing with. On the header file, it defines the fs magic number as #define UX_MAGIC 0x58494e55 1. which means, will it assign this magic number to ALL files created on this sample fs? That can't be so. Otherwise, why we need to define a magic number? 2. I assume, magic number will be assigned to files by the tools which we use to create the files(like vi, cat, etc). Is this correct? 3. It seems, windows files also have the magic numbers. let's say I copy some files from windows to Linux. We should have the common magic numbers between different Operating systems, so there won't be confusions. I mean, is there any standards common for all os's files magic numbers?!? Best regards Sekar

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swap space - which subsystem
by inventsekar Jan. 18, 2018

Jan. 18, 2018

1. so I tried to find out which subsystem the swap space comes under.. when I googled for list of subsystems Linux architecture, no luck. Between, I found out that kernel map, which gives me kind of subsystems/modules. Is there any documentation/links for list of subsystems on Linux?!?! 2. it looks like swap space itself a separate subsystem/module. I thought to subscribe to some lkml dl for swap, but I am not finding any DL at all. Please suggest. On Jan 15, 2018 11:52 PM, "inventsekar" <inventsekar(a)gmail.com> wrote: Hi All, I have been reading about swap space and got these questions... 1. Btrfs was the only one fs which got this below issue or any other fs also? 2. The other way around - is there any FS which is best suitable (best performance) for swap file? 2. Is this issue still there or the wiki isn't updated? *https://wiki.archlinux.org/index.php/swap <https://wiki.archlinux.org/index.php/swap>* *Warning:* Btrfs <https://wiki.archlinux.org/index.php/Btrfs> does not support swap files. Failure to heed this warning may result in file system corruption. While a swap file may be used on Btrfs when mounted through a loop device, this will result in severely degraded swap performance. Any suggestions, links, documentations please. Best regards Sekar

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Regarding Linux kernel vs Android
by inventsekar Jan. 18, 2018

Jan. 18, 2018

Hi... I tried searching but no luck. Can you please suggest how Linux kernel was modified and became Android?! Just high level ideas are enough. PS - when I send mail to this DL, I thought I would receive my own mail(similar to Google groups DL), as I am already member of the DL, but I am not getting my own mail, so I get confusion whether my mail was sent or not. On the subscription page, I looked for any options, but no luck. Please suggest Best regards Sekar

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OLED Display -- Framebuffer driver to DRM driver conversion required???
by B Mithran Jan. 18, 2018

Jan. 18, 2018

Hi, In my project (Arm processor based), we are using 2 displays. Primary display is for Ubuntu 16.04 OS Gui display and secondary display is for status messages, some small OLED display. This OLED display is framebuffer driver based. My doubt is: 1. Whether I need to convert this framebuffer driver to DRM driver? Is this required? What is the advantages of this? Please provide some inputs on this. -Thanks.

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Bypassing RX_MMAP when it is full
by David Illescas Jan. 18, 2018

Jan. 18, 2018

I would like to enable the following functionality. I do not know whether it already exists or needs to be implemented. I would like to enable/disable logic to egress an incoming frame through some specified port in cases where RX_MMAP is full and would drop. Can this be done through bpf filters or kernel modules? Does it require any changes in the kernel itself? Thank you for your time. -- Sincerely, David Illescas

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Efficient management of emails
by Shyam Saini Jan. 15, 2018

Jan. 15, 2018

Hi Everyone, I have subscribed multiple mailing lists. My question is how do kernel developers and other users manage their emails on daily basis considering the fact that we receive hundreds of mails everyday. One way is to tag each mails with their name for example "NetDev". I'm curious is their any other way? I would one really appreciate if someone will share their experience and use case. Thanks a lot, Shyam

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Query regarding swap space on btrfs
by inventsekar Jan. 15, 2018

Jan. 15, 2018

Hi All, I have been reading about swap space and got these questions... 1. Btrfs was the only one fs which got this below issue or any other fs also? 2. The other way around - is there any FS which is best suitable (best performance) for swap file? 2. Is this issue still there or the wiki isn't updated? *https://wiki.archlinux.org/index.php/swap <https://wiki.archlinux.org/index.php/swap>* *Warning:* Btrfs <https://wiki.archlinux.org/index.php/Btrfs> does not support swap files. Failure to heed this warning may result in file system corruption. While a swap file may be used on Btrfs when mounted through a loop device, this will result in severely degraded swap performance. Any suggestions, links, documentations please. Best regards Sekar

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how to properly use ramoops/pstore
by Arthur LAMBERT Jan. 11, 2018

Jan. 11, 2018

Hi, Im am working on a ARM imx6ul board with custom kernel. I have some freeze issue. I was able to detect that it is a kernel panic. I would like to be able to save across reboot kernel panic log thanks to ramoops feature. I dont have physical access to the board during the kernel panic. Only way for me to understand and fix the issue is to save and store the kernel panic log to send the log to a server later. To enable ramoops, I update my kernel config : [arthur * 4.1.15_2.0.0_nano] cat output/build/linux-4.1.15_2.1.0_v17/.config | grep PSTORE CONFIG_PSTORE=y CONFIG_PSTORE_CONSOLE=y # CONFIG_PSTORE_PMS I configure the ramoops platform data in the board config file of the kernel tree : arthur * 4.1.15_2.0.0_nano] git diff arch/arm diff --git a/arch/arm/mach-imx/mach-imx6ul.c b/arch/arm/mach-imx/mach-imx6ul.c index dcabfb1..5b1d74c 100644 --- a/arch/arm/mach-imx/mach-imx6ul.c +++ b/arch/arm/mach-imx/mach-imx6ul.c @@ -23,6 +23,22 @@ #include "common.h" #include "cpuidle.h" #include "hardware.h" +#include <linux/pstore_ram.h> +#include <linux/memblock.h> +static struct ramoops_platform_data ramoops_data = { + .mem_address = 0x80000000, + .mem_size = 0x00005000, // 5 Mb ?? + .record_size = 0x00001000, // 1 Mb + .dump_oops = 1, +}; + +static struct platform_device ramoops_dev = { + .name = "ramoops", + .dev = { + .platform_data = &ramoops_data, + }, +}; + static void __init imx6ul_enet_clk_init(void) { @@ -169,6 +185,15 @@ static inline void imx6ul_enet_init(void) static void __init imx6ul_init_machine(void) { struct device *parent; + int ret; + + ret = platform_device_register(&ramoops_dev); + if (ret) { + printk(KERN_ERR "unable to register platform device\n"); + return; + } + /* Do I need that ???? */ + //memblock_reserve(ramoops_data.mem_address, ramoops_data.mem_size); parent = imx_soc_device_init(); if (parent == NULL) Then when I tried to mount the pstore partition : # mount -t pstore -o kmsg_bytes=1000 - /sys/fs/pstore TUTU size : -335633131 ------------[ cut here ]------------ WARNING: CPU: 0 PID: 547 at mm/page_alloc.c:2668 __alloc_pages_nodemask+0x19c/0x838() Modules linked in: bcmdhd CPU: 0 PID: 547 Comm: mount Not tainted 4.1.15 #27 Hardware name: Freescale i.MX6 Ultralite (Device Tree) [<800144bc>] (unwind_backtrace) from [<800121ec>] (show_stack+0x10/0x14) [<800121ec>] (show_stack) from [<80034444>] (warn_slowpath_common+0x80/0xac) [<80034444>] (warn_slowpath_common) from [<8003450c>] (warn_slowpath_null+0x1c/0x24) [<8003450c>] (warn_slowpath_null) from [<800a2704>] (__alloc_pages_nodemask+0x19c/0x838) [<800a2704>] (__alloc_pages_nodemask) from [<800b5a60>] (kmalloc_order+0x10/0x20) [<800b5a60>] (kmalloc_order) from [<80253fa8>] (persistent_ram_save_old+0x118/0x134) [<80253fa8>] (persistent_ram_save_old) from [<80253154>] (ramoops_get_next_prz+0x6c/0x78) [<80253154>] (ramoops_get_next_prz) from [<802531a0>] (ramoops_pstore_read+0x40/0x254) [<802531a0>] (ramoops_pstore_read) from [<80252990>] (pstore_get_records+0xa8/0x2e0) [<80252990>] (pstore_get_records) from [<80251da8>] (pstore_fill_super+0xa8/0xbc) [<80251da8>] (pstore_fill_super) from [<800db540>] (mount_single+0x88/0xac) [<800db540>] (mount_single) from [<800db5d4>] (mount_fs+0x14/0xa4) [<800db5d4>] (mount_fs) from [<800f4688>] (vfs_kern_mount+0x48/0x114) [<800f4688>] (vfs_kern_mount) from [<800f7744>] (do_mount+0x198/0xc28) [<800f7744>] (do_mount) from [<800f84fc>] (SyS_mount+0x74/0xa0) [<800f84fc>] (SyS_mount) from [<8000f2a0>] (ret_fast_syscall+0x0/0x3c) persistent_ram: failed to allocate buffer In the function persistent_ram_save_old for unknow reason the size is negative. Do I miss something ? I also try to patch my kernel to use device tree for ramoops but nothing was working correctly. Same result if I tried to set ramoops settings through kernel parameter. When I try to use other value for ramoops configuration, my kernel is not able to boot anymore. Thanks, Arthur.

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Help! Can't subscribe kernel mail list
by Douglas Su Jan. 11, 2018

Jan. 11, 2018

After I sent 'subscribe linux-kernel' to majordomo(a)vger.kernel.org, I got an undelivered message, in which said: majordomo(a)vger.kernel.org (majordomo(a)vger.kernel.org) Your message wasn't delivered because the destination email system rejected your message for security or policy reasons. For example, the email address might only accept messages from certain senders, or it might not accept certain types of messages, like those larger than a specific size. Contact the recipient (by phone, for example) and work with them and their email admin to determine what policy or setting blocked your message and what you should do to make sure that future messages from you won't be rejected. For more information, see Status code 5.7.1. vger.kernel.org gave this error: Hello [40.92.4.67], for your MAIL FROM address <d...@outlook.com> policy analysis reported: Your address is not liked source for email. I searched Mail list FAQ, but still have no idea. It seems that the vger.kernel.org mail server banned my mail address.

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