Re: [PATCH] reiser4: prevent system lockups

Re: [PATCH] reiser4: prevent system lockups

[Metztli Information Technology]

That is 'one hell of' a shrewd finding, Ed!
> On Tue, Feb 4, 2020 at 4:24 PM Edward Shishkin <edward.shishkin@gmail.com> wrote:
>
> Hi all,
>
> Starting from Linux-4.15, VFS introduces optimizations, which
> are incompatible with Reiser4 (as well as with any FS possessing
> an advanced transaction manager). Here is the problematic commit:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=aa65c29ce1b6e1990cd2c7d8004bbea7ff3aff38
Indeed, I knew *something* had changed but I focused heavily on confirming the validity of my reiser4 hacks; additionally, I began
examining attentively multiple Debian packaging for Linux major.minor changes, custom debian patches, as well as the packaging custom default .config
--believing the Debian Kernel Team modifications might have had introduced the hanging issue, Sir.
>
> The attached patch fixes the problem. This patch is against
> Linux-5.4+reiser4. Please, apply.
5.4.6 [?]

>
> Later I'll prepare backports for all the mentioned kernels and will
> put them on Sourceforge.
Cool! I was notified of your latest reiser4-for-5.4.17.patch.gz release.

> If someone urgently needs a backport, then
> let me know.
>
> Thanks,
> Edward.
Your dedication and outsized efforts toward maintaining and enhancing REISER4 are MUCH ADMIRED and APPRECIATED, Ed, THANK YOU!


Best Professional Regards.

Re: [PATCH] reiser4: prevent system lockups

[Edward Shishkin]

On 02/06/2020 03:12 PM, Metztli Information Technology wrote:
> That is 'one hell of' a shrewd finding, Ed!
>> On Tue, Feb 4, 2020 at 4:24 PM Edward Shishkin <edward.shishkin@gmail.com> wrote:
>>
>> Hi all,
>>
>> Starting from Linux-4.15, VFS introduces optimizations, which
>> are incompatible with Reiser4 (as well as with any FS possessing
>> an advanced transaction manager). Here is the problematic commit:
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=aa65c29ce1b6e1990cd2c7d8004bbea7ff3aff38
> Indeed, I knew *something* had changed but I focused heavily on confirming the validity of my reiser4 hacks; additionally, I began
> examining attentively multiple Debian packaging for Linux major.minor changes, custom debian patches, as well as the packaging custom default .config
> --believing the Debian Kernel Team modifications might have had introduced the hanging issue, Sir.
>> The attached patch fixes the problem. This patch is against
>> Linux-5.4+reiser4. Please, apply.
> 5.4.6 [?]

Yes, against Linux-5.4.X+reiser4-for-5.4.6.

Also I've uploaded reiser4-for-5.4.17, which already contains that fixup:
https://sourceforge.net/projects/reiser4/files/reiser4-for-linux-5.x/

Edward.

>
>> Later I'll prepare backports for all the mentioned kernels and will
>> put them on Sourceforge.
> Cool! I was notified of your latest reiser4-for-5.4.17.patch.gz release.
>
>> If someone urgently needs a backport, then
>> let me know.
>>
>> Thanks,
>> Edward.
> Your dedication and outsized efforts toward maintaining and enhancing REISER4 are MUCH ADMIRED and APPRECIATED, Ed, THANK YOU!
>
>
> Best Professional Regards.

[PATCH] reiser4: prevent system lockups

[Edward Shishkin]

[-- Attachment #1: Type: text/plain, Size: 583 bytes --]

Hi all,

Starting from Linux-4.15, VFS introduces optimizations, which
are incompatible with Reiser4 (as well as with any FS possessing
an advanced transaction manager). Here is the problematic commit:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=aa65c29ce1b6e1990cd2c7d8004bbea7ff3aff38

The attached patch fixes the problem. This patch is against
Linux-5.4+reiser4. Please, apply.

Later I'll prepare backports for all the mentioned kernels and will
put them on Sourceforge. If someone urgently needs a backport, then
let me know.

Thanks,
Edward.

[-- Attachment #2: reiser4-fix-lockup.patch --]
[-- Type: text/x-patch, Size: 2137 bytes --]

diff -urN linux-5.4.6/fs/reiser4/page_cache.c linux-5.4.6.patched/fs/reiser4/page_cache.c
--- linux-5.4.6/fs/reiser4/page_cache.c	2020-02-05 00:08:07.121592727 +0100
+++ linux-5.4.6.patched/fs/reiser4/page_cache.c	2020-02-05 00:09:44.508645047 +0100
@@ -549,7 +549,8 @@
 	 */
 	.releasepage = reiser4_releasepage,
 	.direct_IO = NULL,
-	.migratepage = reiser4_migratepage
+	.migratepage = reiser4_migratepage,
+	.batch_lock_tabu = 1
 };
 
 /* called just before page is released (no longer used by reiser4). Callers:
diff -urN linux-5.4.6/fs/reiser4/plugin/object.c linux-5.4.6.patched/fs/reiser4/plugin/object.c
--- linux-5.4.6/fs/reiser4/plugin/object.c	2020-02-05 00:08:07.129592814 +0100
+++ linux-5.4.6.patched/fs/reiser4/plugin/object.c	2020-02-05 00:09:44.508645047 +0100
@@ -150,7 +150,8 @@
 	.bmap = reiser4_bmap_dispatch,
 	.invalidatepage = reiser4_invalidatepage,
 	.releasepage = reiser4_releasepage,
-	.migratepage = reiser4_migratepage
+	.migratepage = reiser4_migratepage,
+	.batch_lock_tabu = 1
 };
 
 /* VFS methods for symlink files */
diff -urN linux-5.4.6/include/linux/fs.h linux-5.4.6.patched/include/linux/fs.h
--- linux-5.4.6/include/linux/fs.h	2020-02-05 00:08:07.135592878 +0100
+++ linux-5.4.6.patched/include/linux/fs.h	2020-02-05 00:09:21.339394689 +0100
@@ -409,6 +409,7 @@
 	int (*swap_activate)(struct swap_info_struct *sis, struct file *file,
 				sector_t *span);
 	void (*swap_deactivate)(struct file *file);
+	int batch_lock_tabu;
 };
 
 extern const struct address_space_operations empty_aops;
diff -urN linux-5.4.6/mm/truncate.c linux-5.4.6.patched/mm/truncate.c
--- linux-5.4.6/mm/truncate.c	2019-12-21 11:05:23.000000000 +0100
+++ linux-5.4.6.patched/mm/truncate.c	2020-02-05 00:09:21.339394689 +0100
@@ -360,6 +360,13 @@
 				continue;
 			}
 			pagevec_add(&locked_pvec, page);
+			if (mapping->a_ops->batch_lock_tabu)
+				/*
+				 * the file system doesn't allow to hold
+				 * many pages locked, while calling
+				 * ->invalidatepage() for one of them
+				 */
+				break;
 		}
 		for (i = 0; i < pagevec_count(&locked_pvec); i++)
 			truncate_cleanup_page(mapping, locked_pvec.pages[i]);