Add proposed fix for data loss on md raid0 when discard is used (FS#45040).

PKGBUILD

@@ -5,7 +5,7 @@ pkgbase=linux               # Build stock -ARCH kernel
 #pkgbase=linux-custom       # Build kernel with a different name
 _srcname=linux-4.0
 pkgver=4.0.4
-pkgrel=1
+pkgrel=2
 arch=('i686' 'x86_64')
 url="http://www.kernel.org/"
 license=('GPL2')
@@ -19,6 +19,7 @@ source=("https://www.kernel.org/pub/linux/kernel/v4.x/${_srcname}.tar.xz"
         'config' 'config.x86_64'
         # standard config files for mkinitcpio ramdisk
         'linux.preset'
+        'md-raid0-fix-restore-to-sector-variable-in-raid0_mak.patch'
         'change-default-console-loglevel.patch')
 sha256sums=('0f2f7d44979bc8f71c4fc5d3308c03499c26a824dd311fdf6eef4dee0d7d5991'
             'SKIP'
@@ -27,6 +28,7 @@ sha256sums=('0f2f7d44979bc8f71c4fc5d3308c03499c26a824dd311fdf6eef4dee0d7d5991'
             'e8d639582697f22333a96aa1614bcf5d9bcf2e6683a3d5296f9cfc64843606f1'
             '5dadd75693e512b77f87f5620e470405b943373613eaf4df561037e9296453be'
             'f0d90e756f14533ee67afda280500511a62465b4f76adcc5effa95a40045179c'
+            'bc83293e64653d60793708a0e277741f57c018f5ea3551a8aff3a220df917ceb'
             '1256b241cd477b265a3c2d64bdc19ffe3c9bbcee82ea3994c590c2c76e767d99')
 validpgpkeys=(
               'ABAF11C65A2970B130ABE3C479BE3E4300411886' # Linus Torvalds
@@ -44,6 +46,9 @@ prepare() {
   # add latest fixes from stable queue, if needed
   # http://git.kernel.org/?p=linux/kernel/git/stable/stable-queue.git
 
+  # https://bugzilla.kernel.org/show_bug.cgi?id=98501
+  patch -Np1 -i "${srcdir}/md-raid0-fix-restore-to-sector-variable-in-raid0_mak.patch"
+
   # set DEFAULT_CONSOLE_LOGLEVEL to 4 (same value as the 'quiet' kernel param)
   # remove this when a Kconfig knob is made available by upstream
   # (relevant patch sent upstream: https://lkml.org/lkml/2011/7/26/227)

md-raid0-fix-restore-to-sector-variable-in-raid0_mak.patch

@@ -0,0 +1,50 @@
+From a81157768a00e8cf8a7b43b5ea5cac931262374f Mon Sep 17 00:00:00 2001
+From: Eric Work <work.eric@gmail.com>
+Date: Mon, 18 May 2015 23:26:23 -0700
+Subject: [PATCH] md/raid0: fix restore to sector variable in
+ raid0_make_request
+
+The variable "sector" in "raid0_make_request()" was improperly updated
+by a call to "sector_div()" which modifies its first argument in place.
+Commit 47d68979cc968535cb87f3e5f2e6a3533ea48fbd restored this variable
+after the call for later re-use.  Unfortunetly the restore was done after
+the referenced variable "bio" was advanced.  This lead to the original
+value and the restored value being different.  Here we move this line to
+the proper place.
+
+One observed side effect of this bug was discarding a file though
+unlinking would cause an unrelated file's contents to be discarded.
+
+Signed-off-by: NeilBrown <neilb@suse.de>
+Fixes: 47d68979cc96 ("md/raid0: fix bug with chunksize not a power of 2.")
+Cc: stable@vger.kernel.org (any that received above backport)
+URL: https://bugzilla.kernel.org/show_bug.cgi?id=98501
+---
+ drivers/md/raid0.c | 4 +++-
+ 1 file changed, 3 insertions(+), 1 deletion(-)
+
+diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
+index 6a68ef5..efb654e 100644
+--- a/drivers/md/raid0.c
++++ b/drivers/md/raid0.c
+@@ -524,6 +524,9 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
+ 			 ? (sector & (chunk_sects-1))
+ 			 : sector_div(sector, chunk_sects));
+ 
++		/* Restore due to sector_div */
++		sector = bio->bi_iter.bi_sector;
++
+ 		if (sectors < bio_sectors(bio)) {
+ 			split = bio_split(bio, sectors, GFP_NOIO, fs_bio_set);
+ 			bio_chain(split, bio);
+@@ -531,7 +534,6 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
+ 			split = bio;
+ 		}
+ 
+-		sector = bio->bi_iter.bi_sector;
+ 		zone = find_zone(mddev->private, &sector);
+ 		tmp_dev = map_sector(mddev, zone, sector, &sector);
+ 		split->bi_bdev = tmp_dev->bdev;
+-- 
+2.4.1
+