linux-kernel - [PATCH 2/3] resource: Include resource end in walk

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Date:   Thu, 27 Sep 2018 09:22:02 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Lianbo Jiang <lijiang@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
        kexec@...ts.infradead.org, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, x86@...nel.org, akpm@...ux-foundation.org,
        dan.j.williams@...el.com, thomas.lendacky@....com,
        baiyaowei@...s.chinamobile.com, tiwai@...e.de, bp@...e.de,
        brijesh.singh@....com, dyoung@...hat.com, bhe@...hat.com
Subject: [PATCH 2/3] resource: Include resource end in walk_*() interfaces

From: Bjorn Helgaas <bhelgaas@...gle.com>

find_next_iomem_res() finds an iomem resource that covers part of a range
described by "start, end".  All callers expect that range to be inclusive,
i.e., both start and end are included, but find_next_iomem_res() doesn't
handle the end address correctly.

If it finds an iomem resource that contains exactly the end address, it
skips it, e.g., if "start, end" is [0x0-0x10000] and there happens to be an
iomem resource [mem 0x10000-0x10000] (the single byte at 0x10000), we skip
it:

  find_next_iomem_res(...)
  {
    start = 0x0;
    end = 0x10000;
    for (p = next_resource(...)) {
      # p->start = 0x10000;
      # p->end = 0x10000;
      # we *should* return this resource, but this condition is false:
      if ((p->end >= start) && (p->start < end))
        break;

Adjust find_next_iomem_res() so it allows a resource that includes the
single byte at the end of the range.  This is a corner case that we
probably don't see in practice.

Fixes: 58c1b5b07907 ("[PATCH] memory hotadd fixes: find_next_system_ram catch range fix")
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
---
 kernel/resource.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 30e1bc68503b..155ec873ea4d 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -319,7 +319,7 @@ int release_resource(struct resource *old)
 EXPORT_SYMBOL(release_resource);
 
 /*
- * Finds the lowest iomem resource existing within [res->start.res->end).
+ * Finds the lowest iomem resource existing within [res->start..res->end].
  * The caller must specify res->start, res->end, res->flags, and optionally
  * desc.  If found, returns 0, res is overwritten, if not found, returns -1.
  * This function walks the whole tree and not just first level children until
@@ -352,7 +352,7 @@ static int find_next_iomem_res(struct resource *res, unsigned long desc,
 			p = NULL;
 			break;
 		}
-		if ((p->end >= start) && (p->start < end))
+		if ((p->end >= start) && (p->start <= end))
 			break;
 	}