mainlining shenanigans
8615b94f02
Running stress test io_paral (A pressure ubi test in mtd-utils) on an UBI device with fewer PEBs (fastmap enabled) may cause ENOSPC errors and make UBI device read-only, but there are still free PEBs on the UBI device. This problem can be easily reproduced by performing the following steps on a 2-core machine: $ modprobe nandsim first_id_byte=0x20 second_id_byte=0x33 parts=80 $ modprobe ubi mtd="0,0" fm_autoconvert $ ./io_paral /dev/ubi0 We may see the following verbose: (output) [io_paral] update_volume():108: failed to write 380 bytes at offset 95920 of volume 2 [io_paral] update_volume():109: update: 97088 bytes [io_paral] write_thread():227: function pwrite() failed with error 28 (No space left on device) [io_paral] write_thread():229: cannot write 15872 bytes to offs 31744, wrote -1 (dmesg) ubi0 error: ubi_wl_get_peb [ubi]: Unable to get a free PEB from user WL pool ubi0 warning: ubi_eba_write_leb [ubi]: switch to read-only mode CPU: 0 PID: 2027 Comm: io_paral Not tainted 5.3.0-rc2-00001-g5986cd0 #9 ubi0 warning: try_write_vid_and_data [ubi]: failed to write VID header to LEB 2:5, PEB 18 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0 -0-ga698c8995f-prebuilt.qemu.org 04/01/2014 Call Trace: dump_stack+0x85/0xba ubi_eba_write_leb+0xa1e/0xa40 [ubi] vol_cdev_write+0x307/0x520 [ubi] vfs_write+0xfa/0x280 ksys_pwrite64+0xc5/0xe0 __x64_sys_pwrite64+0x22/0x30 do_syscall_64+0xbf/0x440 In function ubi_wl_get_peb, the operation of filling the pool (ubi_update_fastmap) with free PEBs and fetching a free PEB from the pool is not atomic. After thread A filling the pool with free PEB, free PEB may be taken away by thread B. When thread A checks the expression again, the condition is still unsatisfactory. At this time, there may still be free PEBs on UBI that can be filled into the pool. This patch increases the number of attempts to obtain PEB. An extreme case (No free PEBs left after creating test volumes) has been tested on different type of machines for 100 times. The biggest number of attempts are shown below: x86_64 arm64 2-core 4 4 4-core 8 4 8-core 4 4 Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com> Signed-off-by: Richard Weinberger <richard@nod.at> |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.