| Message ID | 20180925091457.28651-6-david@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: online/offline_pages called w.o. mem_hotplug_lock | expand |
On Tue, Sep 25, 2018 at 11:14:56AM +0200, David Hildenbrand wrote: > Let's perform all checking + offlining + removing under > device_hotplug_lock, so nobody can mess with these devices via > sysfs concurrently. > > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Paul Mackerras <paulus@samba.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Rashmica Gupta <rashmica.g@gmail.com> > Cc: Balbir Singh <bsingharora@gmail.com> > Cc: Michael Neuling <mikey@neuling.org> > Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com> > Reviewed-by: Rashmica Gupta <rashmica.g@gmail.com> > Signed-off-by: David Hildenbrand <david@redhat.com> > --- > arch/powerpc/platforms/powernv/memtrace.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c > index fdd48f1a39f7..d84d09c56af9 100644 > --- a/arch/powerpc/platforms/powernv/memtrace.c > +++ b/arch/powerpc/platforms/powernv/memtrace.c > @@ -70,6 +70,7 @@ static int change_memblock_state(struct memory_block *mem, void *arg) > return 0; > } > > +/* called with device_hotplug_lock held */ > static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages) > { > u64 end_pfn = start_pfn + nr_pages - 1; > @@ -111,6 +112,7 @@ static u64 memtrace_alloc_node(u32 nid, u64 size) > end_pfn = round_down(end_pfn - nr_pages, nr_pages); > > for (base_pfn = end_pfn; base_pfn > start_pfn; base_pfn -= nr_pages) { > + lock_device_hotplug(); Why not grab the lock before the for loop? That way we can avoid bad cases like a large node being scanned for a small number of pages (nr_pages). Ideally we need a cond_resched() in the loop, but I guess offline_pages() has one. Acked-by: Balbir Singh <bsingharora@gmail.com>
On 25/09/2018 14:15, Balbir Singh wrote: > On Tue, Sep 25, 2018 at 11:14:56AM +0200, David Hildenbrand wrote: >> Let's perform all checking + offlining + removing under >> device_hotplug_lock, so nobody can mess with these devices via >> sysfs concurrently. >> >> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> >> Cc: Paul Mackerras <paulus@samba.org> >> Cc: Michael Ellerman <mpe@ellerman.id.au> >> Cc: Rashmica Gupta <rashmica.g@gmail.com> >> Cc: Balbir Singh <bsingharora@gmail.com> >> Cc: Michael Neuling <mikey@neuling.org> >> Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com> >> Reviewed-by: Rashmica Gupta <rashmica.g@gmail.com> >> Signed-off-by: David Hildenbrand <david@redhat.com> >> --- >> arch/powerpc/platforms/powernv/memtrace.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c >> index fdd48f1a39f7..d84d09c56af9 100644 >> --- a/arch/powerpc/platforms/powernv/memtrace.c >> +++ b/arch/powerpc/platforms/powernv/memtrace.c >> @@ -70,6 +70,7 @@ static int change_memblock_state(struct memory_block *mem, void *arg) >> return 0; >> } >> >> +/* called with device_hotplug_lock held */ >> static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages) >> { >> u64 end_pfn = start_pfn + nr_pages - 1; >> @@ -111,6 +112,7 @@ static u64 memtrace_alloc_node(u32 nid, u64 size) >> end_pfn = round_down(end_pfn - nr_pages, nr_pages); >> >> for (base_pfn = end_pfn; base_pfn > start_pfn; base_pfn -= nr_pages) { >> + lock_device_hotplug(); > > Why not grab the lock before the for loop? That way we can avoid bad cases like a > large node being scanned for a small number of pages (nr_pages). Ideally we need > a cond_resched() in the loop, but I guess offline_pages() has one. Yes, it does. I can move it out of the loop, thanks! > > Acked-by: Balbir Singh <bsingharora@gmail.com> >
diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c index fdd48f1a39f7..d84d09c56af9 100644 --- a/arch/powerpc/platforms/powernv/memtrace.c +++ b/arch/powerpc/platforms/powernv/memtrace.c @@ -70,6 +70,7 @@ static int change_memblock_state(struct memory_block *mem, void *arg) return 0; } +/* called with device_hotplug_lock held */ static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages) { u64 end_pfn = start_pfn + nr_pages - 1; @@ -111,6 +112,7 @@ static u64 memtrace_alloc_node(u32 nid, u64 size) end_pfn = round_down(end_pfn - nr_pages, nr_pages); for (base_pfn = end_pfn; base_pfn > start_pfn; base_pfn -= nr_pages) { + lock_device_hotplug(); if (memtrace_offline_pages(nid, base_pfn, nr_pages) == true) { /* * Remove memory in memory block size chunks so that @@ -118,7 +120,6 @@ static u64 memtrace_alloc_node(u32 nid, u64 size) * we never try to remove memory that spans two iomem * resources. */ - lock_device_hotplug(); end_pfn = base_pfn + nr_pages; for (pfn = base_pfn; pfn < end_pfn; pfn += bytes>> PAGE_SHIFT) { __remove_memory(nid, pfn << PAGE_SHIFT, bytes); @@ -126,6 +127,7 @@ static u64 memtrace_alloc_node(u32 nid, u64 size) unlock_device_hotplug(); return base_pfn << PAGE_SHIFT; } + unlock_device_hotplug(); } return 0;