| Message ID | 20180817090017.17610-4-osalvador@techadventures.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Refactoring for remove_memory_section/unregister_mem_sect_under_nodes | expand |
On 17.08.2018 11:00, Oscar Salvador wrote: > From: Oscar Salvador <osalvador@suse.de> > > Currently, unregister_mem_sect_under_nodes() tries to allocate a nodemask_t > in order to check whithin the loop which nodes have already been unlinked, > so we do not repeat the operation on them. > > NODEMASK_ALLOC calls kmalloc() if NODES_SHIFT > 8, otherwise > it just declares a nodemask_t variable whithin the stack. > > Since kmalloc() can fail, we actually check whether NODEMASK_ALLOC failed > or not, and we return -ENOMEM accordingly. > remove_memory_section() does not check for the return value though. > It is pretty rare that such a tiny allocation can fail, but if it does, > we will be left with dangled symlinks under /sys/devices/system/node/, > since the mem_blk's directories will be removed no matter what > unregister_mem_sect_under_nodes() returns. > > One way to solve this is to check whether unlinked_nodes is NULL or not. > In the case it is not, we can just use it as before, but if it is NULL, > we can just skip the node_test_and_set check, and call sysfs_remove_link() > unconditionally. > This is harmless as sysfs_remove_link() backs off somewhere down the chain > in case the link has already been removed. > This method was presented in v3 of the path [1]. > > But since the maximum number of nodes we can have is 1024, > when NODES_SHIFT = 10, that gives us a nodemask_t of 128 bytes. > Although everything depends on how deep the stack is, I think we can afford > to define the nodemask_t variable whithin the stack. > > That simplifies the code, and we do not need to worry about untested error > code paths. > > If we see that this causes troubles with the stack, we can always return to [1]. > > [1] https://patchwork.kernel.org/patch/10566673/ > > Signed-off-by: Oscar Salvador <osalvador@suse.de> > --- > drivers/base/node.c | 16 ++++++---------- > include/linux/node.h | 5 ++--- > 2 files changed, 8 insertions(+), 13 deletions(-) > > diff --git a/drivers/base/node.c b/drivers/base/node.c > index dd3bdab230b2..6b8c9b4537c9 100644 > --- a/drivers/base/node.c > +++ b/drivers/base/node.c > @@ -449,35 +449,31 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg) > } > > /* unregister memory section under all nodes that it spans */ > -int unregister_mem_sect_under_nodes(struct memory_block *mem_blk, > +void unregister_mem_sect_under_nodes(struct memory_block *mem_blk, > unsigned long phys_index) I am a friend of fixing up alignment of other parameters. > { > - NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL); > + nodemask_t unlinked_nodes; > unsigned long pfn, sect_start_pfn, sect_end_pfn; > > - if (!unlinked_nodes) > - return -ENOMEM; > - nodes_clear(*unlinked_nodes); > + nodes_clear(unlinked_nodes); > > sect_start_pfn = section_nr_to_pfn(phys_index); > sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1; > for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) { > - int nid; > + int nid = get_nid_for_pfn(pfn); > > - nid = get_nid_for_pfn(pfn); > if (nid < 0) > continue; > if (!node_online(nid)) > continue; > - if (node_test_and_set(nid, *unlinked_nodes)) > + if (node_test_and_set(nid, unlinked_nodes)) > continue; > + > sysfs_remove_link(&node_devices[nid]->dev.kobj, > kobject_name(&mem_blk->dev.kobj)); > sysfs_remove_link(&mem_blk->dev.kobj, > kobject_name(&node_devices[nid]->dev.kobj)); > } > - NODEMASK_FREE(unlinked_nodes); > - return 0; > } > > int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn) > diff --git a/include/linux/node.h b/include/linux/node.h > index 257bb3d6d014..1203378e596a 100644 > --- a/include/linux/node.h > +++ b/include/linux/node.h > @@ -72,7 +72,7 @@ extern int register_cpu_under_node(unsigned int cpu, unsigned int nid); > extern int unregister_cpu_under_node(unsigned int cpu, unsigned int nid); > extern int register_mem_sect_under_node(struct memory_block *mem_blk, > void *arg); > -extern int unregister_mem_sect_under_nodes(struct memory_block *mem_blk, > +extern void unregister_mem_sect_under_nodes(struct memory_block *mem_blk, > unsigned long phys_index); dito > > #ifdef CONFIG_HUGETLBFS > @@ -105,10 +105,9 @@ static inline int register_mem_sect_under_node(struct memory_block *mem_blk, > { > return 0; > } > -static inline int unregister_mem_sect_under_nodes(struct memory_block *mem_blk, > +static inline void unregister_mem_sect_under_nodes(struct memory_block *mem_blk, > unsigned long phys_index) dito > { > - return 0; > } > > static inline void register_hugetlbfs_with_node(node_registration_func_t reg, > We'll find out if we have enough stack :) But this is definitely simpler.
On Fri, Aug 17, 2018 at 11:00:16AM +0200, Oscar Salvador wrote:
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
Pavel, could you please review this?
AFAIK, the change made sense to you.
Andrew was about to take the patchset after the merge window,
but I think that a Reviewed-by would still make sense.
Thanks
On 8/17/18 5:00 AM, Oscar Salvador wrote: > From: Oscar Salvador <osalvador@suse.de> > > Currently, unregister_mem_sect_under_nodes() tries to allocate a nodemask_t > in order to check whithin the loop which nodes have already been unlinked, > so we do not repeat the operation on them. > > NODEMASK_ALLOC calls kmalloc() if NODES_SHIFT > 8, otherwise > it just declares a nodemask_t variable whithin the stack. > > Since kmalloc() can fail, we actually check whether NODEMASK_ALLOC failed > or not, and we return -ENOMEM accordingly. > remove_memory_section() does not check for the return value though. > It is pretty rare that such a tiny allocation can fail, but if it does, > we will be left with dangled symlinks under /sys/devices/system/node/, > since the mem_blk's directories will be removed no matter what > unregister_mem_sect_under_nodes() returns. > > One way to solve this is to check whether unlinked_nodes is NULL or not. > In the case it is not, we can just use it as before, but if it is NULL, > we can just skip the node_test_and_set check, and call sysfs_remove_link() > unconditionally. > This is harmless as sysfs_remove_link() backs off somewhere down the chain > in case the link has already been removed. > This method was presented in v3 of the path [1]. > > But since the maximum number of nodes we can have is 1024, > when NODES_SHIFT = 10, that gives us a nodemask_t of 128 bytes. > Although everything depends on how deep the stack is, I think we can afford > to define the nodemask_t variable whithin the stack. > > That simplifies the code, and we do not need to worry about untested error > code paths. > > If we see that this causes troubles with the stack, we can always return to [1]. > > Signed-off-by: Oscar Salvador <osalvador@suse.de> LGTM: Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com> Thank you, Pavel
diff --git a/drivers/base/node.c b/drivers/base/node.c index dd3bdab230b2..6b8c9b4537c9 100644 --- a/drivers/base/node.c +++ b/drivers/base/node.c @@ -449,35 +449,31 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg) } /* unregister memory section under all nodes that it spans */ -int unregister_mem_sect_under_nodes(struct memory_block *mem_blk, +void unregister_mem_sect_under_nodes(struct memory_block *mem_blk, unsigned long phys_index) { - NODEMASK_ALLOC(nodemask_t, unlinked_nodes, GFP_KERNEL); + nodemask_t unlinked_nodes; unsigned long pfn, sect_start_pfn, sect_end_pfn; - if (!unlinked_nodes) - return -ENOMEM; - nodes_clear(*unlinked_nodes); + nodes_clear(unlinked_nodes); sect_start_pfn = section_nr_to_pfn(phys_index); sect_end_pfn = sect_start_pfn + PAGES_PER_SECTION - 1; for (pfn = sect_start_pfn; pfn <= sect_end_pfn; pfn++) { - int nid; + int nid = get_nid_for_pfn(pfn); - nid = get_nid_for_pfn(pfn); if (nid < 0) continue; if (!node_online(nid)) continue; - if (node_test_and_set(nid, *unlinked_nodes)) + if (node_test_and_set(nid, unlinked_nodes)) continue; + sysfs_remove_link(&node_devices[nid]->dev.kobj, kobject_name(&mem_blk->dev.kobj)); sysfs_remove_link(&mem_blk->dev.kobj, kobject_name(&node_devices[nid]->dev.kobj)); } - NODEMASK_FREE(unlinked_nodes); - return 0; } int link_mem_sections(int nid, unsigned long start_pfn, unsigned long end_pfn) diff --git a/include/linux/node.h b/include/linux/node.h index 257bb3d6d014..1203378e596a 100644 --- a/include/linux/node.h +++ b/include/linux/node.h @@ -72,7 +72,7 @@ extern int register_cpu_under_node(unsigned int cpu, unsigned int nid); extern int unregister_cpu_under_node(unsigned int cpu, unsigned int nid); extern int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg); -extern int unregister_mem_sect_under_nodes(struct memory_block *mem_blk, +extern void unregister_mem_sect_under_nodes(struct memory_block *mem_blk, unsigned long phys_index); #ifdef CONFIG_HUGETLBFS @@ -105,10 +105,9 @@ static inline int register_mem_sect_under_node(struct memory_block *mem_blk, { return 0; } -static inline int unregister_mem_sect_under_nodes(struct memory_block *mem_blk, +static inline void unregister_mem_sect_under_nodes(struct memory_block *mem_blk, unsigned long phys_index) { - return 0; } static inline void register_hugetlbfs_with_node(node_registration_func_t reg,