From cab114c5ca870e5f1b57fb2602cd9a038271c2e0 Mon Sep 17 00:00:00 2001 From: Corey Hickey Date: Mon, 11 Feb 2019 17:18:38 -0800 Subject: [PATCH] Fix reshape for decreasing data offset Git-commit: cab114c5ca870e5f1b57fb2602cd9a038271c2e0 Patch-mainline: mdadm-4.1+ References: jsc#SLE-10078, jsc#SLE-9348 ...when not changing the number of disks. This patch needs context to explain. These are the relevant parts of the original code (condensed and annotated): if (dir > 0) { /* Increase data offset (reshape backwards) */ if (data_offset < sd->data_offset + min) { pr_err("--data-offset too small on %s\n", dn); goto release; } } else { /* Decrease data offset (reshape forwards) */ if (data_offset < sd->data_offset - min) { pr_err("--data-offset too small on %s\n", dn); goto release; } } When this code is reached, mdadm has already decided on a reshape direction. When increasing the data offset, the reshape runs backwards (dir==1); when decreasing the data offset, the reshape runs forwards (dir==-1). The conditional within the backwards reshape is correct: the requested offset must be larger than the old offset plus a minimum delta; thus the reshape has room to work. For the forwards reshape, the requested offset needs to be smaller than the old offset minus a minimum delta; to do this correctly, the comparison must be reversed. Also update the error message. Note: I have tested this change on a RAID 5 on Linux 4.18.0 and verified that there were no errors from the kernel and that the device data remained intact. I do not know if there are considerations for different RAID levels. Signed-off-by: Corey Hickey Signed-off-by: Jes Sorensen Signed-off-by: Coly Li --- Grow.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/Grow.c b/Grow.c index 6d32661..764374f 100644 --- a/Grow.c +++ b/Grow.c @@ -2613,8 +2613,8 @@ static int set_new_data_offset(struct mdinfo *sra, struct supertype *st, goto release; } if (data_offset != INVALID_SECTORS && - data_offset < sd->data_offset - min) { - pr_err("--data-offset too small on %s\n", + data_offset > sd->data_offset - min) { + pr_err("--data-offset too large on %s\n", dn); goto release; } -- 2.25.0