linux/drivers/md/md-linear.h

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License cleanup: add SPDX GPL-2.0 license identifier to files with no license Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-01 14:07:57 +00:00
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINEAR_H
#define _LINEAR_H
struct dev_info {
struct md_rdev *rdev;
sector_t end_sector;
};
struct linear_conf
{
struct rcu_head rcu;
sector_t array_sectors;
md linear: fix a race between linear_add() and linear_congested() Recently I receive a bug report that on Linux v3.0 based kerenl, hot add disk to a md linear device causes kernel crash at linear_congested(). From the crash image analysis, I find in linear_congested(), mddev->raid_disks contains value N, but conf->disks[] only has N-1 pointers available. Then a NULL pointer deference crashes the kernel. There is a race between linear_add() and linear_congested(), RCU stuffs used in these two functions cannot avoid the race. Since Linuv v4.0 RCU code is replaced by introducing mddev_suspend(). After checking the upstream code, it seems linear_congested() is not called in generic_make_request() code patch, so mddev_suspend() cannot provent it from being called. The possible race still exists. Here I explain how the race still exists in current code. For a machine has many CPUs, on one CPU, linear_add() is called to add a hard disk to a md linear device; at the same time on other CPU, linear_congested() is called to detect whether this md linear device is congested before issuing an I/O request onto it. Now I use a possible code execution time sequence to demo how the possible race happens, seq linear_add() linear_congested() 0 conf=mddev->private 1 oldconf=mddev->private 2 mddev->raid_disks++ 3 for (i=0; i<mddev->raid_disks;i++) 4 bdev_get_queue(conf->disks[i].rdev->bdev) 5 mddev->private=newconf In linear_add() mddev->raid_disks is increased in time seq 2, and on another CPU in linear_congested() the for-loop iterates conf->disks[i] by the increased mddev->raid_disks in time seq 3,4. But conf with one more element (which is a pointer to struct dev_info type) to conf->disks[] is not updated yet, accessing its structure member in time seq 4 will cause a NULL pointer deference fault. To fix this race, there are 2 parts of modification in the patch, 1) Add 'int raid_disks' in struct linear_conf, as a copy of mddev->raid_disks. It is initialized in linear_conf(), always being consistent with pointers number of 'struct dev_info disks[]'. When iterating conf->disks[] in linear_congested(), use conf->raid_disks to replace mddev->raid_disks in the for-loop, then NULL pointer deference will not happen again. 2) RCU stuffs are back again, and use kfree_rcu() in linear_add() to free oldconf memory. Because oldconf may be referenced as mddev->private in linear_congested(), kfree_rcu() makes sure that its memory will not be released until no one uses it any more. Also some code comments are added in this patch, to make this modification to be easier understandable. This patch can be applied for kernels since v4.0 after commit: 3be260cc18f8 ("md/linear: remove rcu protections in favour of suspend/resume"). But this bug is reported on Linux v3.0 based kernel, for people who maintain kernels before Linux v4.0, they need to do some back back port to this patch. Changelog: - V3: add 'int raid_disks' in struct linear_conf, and use kfree_rcu() to replace rcu_call() in linear_add(). - v2: add RCU stuffs by suggestion from Shaohua and Neil. - v1: initial effort. Signed-off-by: Coly Li <colyli@suse.de> Cc: Shaohua Li <shli@fb.com> Cc: Neil Brown <neilb@suse.com> Cc: stable@vger.kernel.org Signed-off-by: Shaohua Li <shli@fb.com>
2017-01-28 13:11:49 +00:00
int raid_disks; /* a copy of mddev->raid_disks */
struct dev_info disks[0];
};
#endif