[Backport release-23.11] zfs: default disable zfs_dmu_offset_next_sync to avoid data corruption

pkgs/os-specific/linux/zfs/patches/disable-zfs-dmu-offset-next-sync-by-default-v2-2.patch

@@ -0,0 +1,44 @@
+From 3ba4ff328ab001d88d7714087d8a89687bc68312 Mon Sep 17 00:00:00 2001
+From: Andrew Marshall <[email protected]>
+Date: Sun, 26 Nov 2023 12:46:18 -0500
+Subject: [PATCH] Disable zfs_dmu_offset_next_sync tunable by default
+
+This helps mitigate a data corruption bug. This was previously defaulted
+to zero, so doing so seems safe.
+
+See https://github.com/openzfs/zfs/issues/11900
+See https://github.com/openzfs/zfs/issues/15526
+---
+ man/man4/zfs.4   | 2 +-
+ module/zfs/dmu.c | 2 +-
+ 2 files changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/man/man4/zfs.4 b/man/man4/zfs.4
+index 4ec52a2fb..2a69a8f54 100644
+--- a/man/man4/zfs.4
++++ b/man/man4/zfs.4
+@@ -1660,7 +1660,7 @@ Allow no-operation writes.
+ The occurrence of nopwrites will further depend on other pool properties
+ .Pq i.a. the checksumming and compression algorithms .
+ .
+-.It Sy zfs_dmu_offset_next_sync Ns = Ns Sy 1 Ns | Ns 0 Pq int
++.It Sy zfs_dmu_offset_next_sync Ns = Ns Sy 0 Ns | Ns 1 Pq int
+ Enable forcing TXG sync to find holes.
+ When enabled forces ZFS to sync data when
+ .Sy SEEK_HOLE No or Sy SEEK_DATA
+diff --git a/module/zfs/dmu.c b/module/zfs/dmu.c
+index ddb29020b..5d37b6f92 100644
+--- a/module/zfs/dmu.c
++++ b/module/zfs/dmu.c
+@@ -82,7 +82,7 @@ static uint_t zfs_per_txg_dirty_frees_percent = 30;
+  * Disabling this option will result in holes never being reported in dirty
+  * files which is always safe.
+  */
+-static int zfs_dmu_offset_next_sync = 1;
++static int zfs_dmu_offset_next_sync = 0;
+
+ /*
+  * Limit the amount we can prefetch with one call to this amount.  This
+-- 
+2.42.0
+

pkgs/os-specific/linux/zfs/stable.nix

@@ -3,7 +3,6 @@
 , stdenv
 , linuxKernel
 , removeLinuxDRM ? false
-, fetchpatch
 , ...
 } @ args:
 
@@ -24,5 +23,9 @@ callPackage ./generic.nix args {
   # this package should point to the latest release.
   version = "2.2.1";
 
+  extraPatches = [
+    ./patches/disable-zfs-dmu-offset-next-sync-by-default-v2-2.patch
+  ];
+
   sha256 = "sha256-2Q/Nhp3YKgMCLPNRNBq5r9U4GeuYlWMWAsjsQy3vFW4=";
 }

pkgs/os-specific/linux/zfs/unstable.nix

@@ -28,4 +28,8 @@ callPackage ./generic.nix args {
   sha256 = "sha256-2Q/Nhp3YKgMCLPNRNBq5r9U4GeuYlWMWAsjsQy3vFW4=";
 
   isUnstable = true;
+
+  extraPatches = [
+    ./patches/disable-zfs-dmu-offset-next-sync-by-default-v2-2.patch
+  ];
 }