s390/vmem: get rid of memory segment list

I can't come up with a satisfying reason why we still need the memory
segment list. We used to represent in the list:
- boot memory
- standby memory added via add_memory()
- loaded dcss segments

When loading/unloading dcss segments, we already track them in a
separate list and check for overlaps
(arch/s390/mm/extmem.c:segment_overlaps_others()) when loading segments.

The overlap check was introduced for some segments in
commit b2300b9efe1b ("[S390] dcssblk: add >2G DCSSs support and stacked
contiguous DCSSs support.")
and was extended to cover all dcss segments in
commit ca57114609d1 ("s390/extmem: remove code for 31 bit addressing
mode").

Although I doubt that overlaps with boot memory and standby memory
are relevant, let's reshuffle the checks in load_segment() to request
the resource first. This will bail out in case we have overlaps with
other resources (esp. boot memory and standby memory). The order
is now different compared to segment_unload() and segment_unload(), but
that should not matter.

This smells like a leftover from ancient times, let's get rid of it. We
can now convert vmem_remove_mapping() into a void function - everybody
ignored the return value already.

Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20200625150029.45019-1-david@redhat.com>
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Tested-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> [DCSS]
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

1 files changed, 13 insertions, 12 deletions

diff --git a/arch/s390/mm/extmem.c b/arch/s390/mm/extmem.c
index 9e0aa7aa03ba..105c09282f8c 100644
--- a/arch/s390/mm/extmem.c
+++ b/arch/s390/mm/extmem.c
@@ -313,15 +313,10 @@ __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long
 		goto out_free;
 	}
 
-	rc = vmem_add_mapping(seg->start_addr, seg->end - seg->start_addr + 1);
-
-	if (rc)
-		goto out_free;
-
 	seg->res = kzalloc(sizeof(struct resource), GFP_KERNEL);
 	if (seg->res == NULL) {
 		rc = -ENOMEM;
-		goto out_shared;
+		goto out_free;
 	}
 	seg->res->flags = IORESOURCE_BUSY | IORESOURCE_MEM;
 	seg->res->start = seg->start_addr;
@@ -335,12 +330,17 @@ __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long
 	if (rc == SEG_TYPE_SC ||
 	    ((rc == SEG_TYPE_SR || rc == SEG_TYPE_ER) && !do_nonshared))
 		seg->res->flags |= IORESOURCE_READONLY;
+
+	/* Check for overlapping resources before adding the mapping. */
 	if (request_resource(&iomem_resource, seg->res)) {
 		rc = -EBUSY;
-		kfree(seg->res);
-		goto out_shared;
+		goto out_free_resource;
 	}
 
+	rc = vmem_add_mapping(seg->start_addr, seg->end - seg->start_addr + 1);
+	if (rc)
+		goto out_resource;
+
 	if (do_nonshared)
 		diag_cc = dcss_diag(&loadnsr_scode, seg->dcss_name,
 				&start_addr, &end_addr);
@@ -351,14 +351,14 @@ __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long
 		dcss_diag(&purgeseg_scode, seg->dcss_name,
 				&dummy, &dummy);
 		rc = diag_cc;
-		goto out_resource;
+		goto out_mapping;
 	}
 	if (diag_cc > 1) {
 		pr_warn("Loading DCSS %s failed with rc=%ld\n", name, end_addr);
 		rc = dcss_diag_translate_rc(end_addr);
 		dcss_diag(&purgeseg_scode, seg->dcss_name,
 				&dummy, &dummy);
-		goto out_resource;
+		goto out_mapping;
 	}
 	seg->start_addr = start_addr;
 	seg->end = end_addr;
@@ -377,11 +377,12 @@ __segment_load (char *name, int do_nonshared, unsigned long *addr, unsigned long
 			(void*) seg->end, segtype_string[seg->vm_segtype]);
 	}
 	goto out;
+ out_mapping:
+	vmem_remove_mapping(seg->start_addr, seg->end - seg->start_addr + 1);
  out_resource:
 	release_resource(seg->res);
+ out_free_resource:
 	kfree(seg->res);
- out_shared:
-	vmem_remove_mapping(seg->start_addr, seg->end - seg->start_addr + 1);
  out_free:
 	kfree(seg);
  out: