| Message ID | 20180813154639.19454-3-osalvador@techadventures.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Refactoring for remove_memory_section/unregister_mem_sect_under_nodes | expand |
On 13.08.2018 17:46, osalvador@techadventures.net wrote: > From: Oscar Salvador <osalvador@suse.de> > > Before calling to unregister_mem_sect_under_nodes(), > remove_memory_section() already checks if we got a valid > memory_block. > > No need to check that again in unregister_mem_sect_under_nodes(). > > Signed-off-by: Oscar Salvador <osalvador@suse.de> > --- > drivers/base/node.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/drivers/base/node.c b/drivers/base/node.c > index 1ac4c36e13bb..dd3bdab230b2 100644 > --- a/drivers/base/node.c > +++ b/drivers/base/node.c > @@ -455,10 +455,6 @@ int unregister_mem_sect_under_nodes(struct memory_block *mem_blk, > NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL); > unsigned long pfn, sect_start_pfn, sect_end_pfn; > > - if (!mem_blk) { > - NODEMASK_FREE(unlinked_nodes); > - return -EFAULT; > - } > if (!unlinked_nodes) > return -ENOMEM; > nodes_clear(*unlinked_nodes); > While it is correct in current code, I wonder if this sanity check should stay. I would completely agree if it would be a static function.
On Tue, Aug 14, 2018 at 11:30:51AM +0200, David Hildenbrand wrote: > > While it is correct in current code, I wonder if this sanity check > should stay. I would completely agree if it would be a static function. Hi David, Well, unregister_mem_sect_under_nodes() __only__ gets called from remove_memory_section(). But remove_memory_section() only calls unregister_mem_sect_under_nodes() IFF mem_blk is not NULL: static int remove_memory_section { ... mem = find_memory_block(section); if (!mem) goto out_unlock; unregister_mem_sect_under_nodes(mem, __section_nr(section)); ... } So, to me keeping the check is redundant, as we already check for it before calling in. Thanks
On 14.08.2018 11:36, Oscar Salvador wrote: > On Tue, Aug 14, 2018 at 11:30:51AM +0200, David Hildenbrand wrote: > >> >> While it is correct in current code, I wonder if this sanity check >> should stay. I would completely agree if it would be a static function. > > Hi David, > > Well, unregister_mem_sect_under_nodes() __only__ gets called from remove_memory_section(). > But remove_memory_section() only calls unregister_mem_sect_under_nodes() IFF mem_blk > is not NULL: > > static int remove_memory_section > { > ... > mem = find_memory_block(section); > if (!mem) > goto out_unlock; > > unregister_mem_sect_under_nodes(mem, __section_nr(section)); > ... > } Yes I know, as I said, if it would be local to a file I would not care. Making this functions never return an error is nice, though (and as you noted, the return value is never checked). I am a friend of stating which conditions a function expects to hold if a function can be called from other parts of the system. Usually I prefer to use BUG_ONs for that (whoever decides to call it can directly see what he as to check before calling) or comments. But comments tend to become obsolete. > > So, to me keeping the check is redundant, as we already check for it before calling in. > > Thanks >
On Tue, Aug 14, 2018 at 11:44:50AM +0200, David Hildenbrand wrote: > > Yes I know, as I said, if it would be local to a file I would not care. > Making this functions never return an error is nice, though (and as you > noted, the return value is never checked). > > I am a friend of stating which conditions a function expects to hold if > a function can be called from other parts of the system. Usually I > prefer to use BUG_ONs for that (whoever decides to call it can directly > see what he as to check before calling) or comments. But comments tend > to become obsolete. Uhm, I think a BUG_ON is too much here. We could replace the check with a WARN_ON, just in case a new function decides to call unregister_mem_sect_under_nodes() in the future. Something like: WARN_ON(!mem_blk) return; In that case, we should get a nice splat in the logs that should tell us who is calling it with an invalid mem_blk.
On 14.08.2018 12:06, Oscar Salvador wrote: > On Tue, Aug 14, 2018 at 11:44:50AM +0200, David Hildenbrand wrote: >> >> Yes I know, as I said, if it would be local to a file I would not care. >> Making this functions never return an error is nice, though (and as you >> noted, the return value is never checked). >> >> I am a friend of stating which conditions a function expects to hold if >> a function can be called from other parts of the system. Usually I >> prefer to use BUG_ONs for that (whoever decides to call it can directly >> see what he as to check before calling) or comments. But comments tend >> to become obsolete. > > Uhm, I think a BUG_ON is too much here. > We could replace the check with a WARN_ON, just in case > a new function decides to call unregister_mem_sect_under_nodes() in the future. > > Something like: > > WARN_ON(!mem_blk) > return; > > In that case, we should get a nice splat in the logs that should tell us > who is calling it with an invalid mem_blk. > Whatever you think is best. I have no idea what the general rules in MM code are. Maybe dropping this check is totally fine.
On Tue, Aug 14, 2018 at 12:09:14PM +0200, David Hildenbrand wrote: > > Whatever you think is best. I have no idea what the general rules in MM > code are. Maybe dropping this check is totally fine. Well, if you ask me, callers should care for validating mem_blk before calling in. But a WARN_ON is not harmful either. Let us just wait to hear more from others. Thanks
diff --git a/drivers/base/node.c b/drivers/base/node.c index 1ac4c36e13bb..dd3bdab230b2 100644 --- a/drivers/base/node.c +++ b/drivers/base/node.c @@ -455,10 +455,6 @@ int unregister_mem_sect_under_nodes(struct memory_block *mem_blk, NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL); unsigned long pfn, sect_start_pfn, sect_end_pfn; - if (!mem_blk) { - NODEMASK_FREE(unlinked_nodes); - return -EFAULT; - } if (!unlinked_nodes) return -ENOMEM; nodes_clear(*unlinked_nodes);