| Message ID | 20181107101830.17405-2-mhocko@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm, memory_hotplug: improve memory offlining failures debugging | expand |
On Wed, 7 Nov 2018 11:18:26 +0100 Michal Hocko <mhocko@kernel.org> wrote: > From: Michal Hocko <mhocko@suse.com> > > __dump_page prints the mapping pointer but that is quite unhelpful > for many reports because the pointer itself only helps to distinguish > anon/ksm mappings from other ones (because of lowest bits > set). Sometimes it would be much more helpful to know what kind of > mapping that is actually and if we know this is a file mapping then also > try to resolve the dentry name. > > ... > > --- a/mm/debug.c > +++ b/mm/debug.c > > ... > > @@ -70,6 +71,18 @@ void __dump_page(struct page *page, const char *reason) > if (PageCompound(page)) > pr_cont(" compound_mapcount: %d", compound_mapcount(page)); > pr_cont("\n"); > + if (PageAnon(page)) > + pr_emerg("anon "); > + else if (PageKsm(page)) > + pr_emerg("ksm "); > + else if (mapping) { > + pr_emerg("%ps ", mapping->a_ops); > + if (mapping->host->i_dentry.first) { > + struct dentry *dentry; > + dentry = container_of(mapping->host->i_dentry.first, struct dentry, d_u.d_alias); > + pr_emerg("name:\"%*s\" ", dentry->d_name.len, dentry->d_name.name); > + } > + } There has to be a better way of printing the filename. It is so often needed. The (poorly named and gleefully undocumented) take_dentry_name_snapshot() looks promising. However it's unclear that __dump_page() is always called from contexts where take_dentry_name_snapshot() and release_dentry_name_snapshot() can be safely called. Probably it's OK, but how to guarantee it?
On Fri 23-11-18 16:04:04, Andrew Morton wrote: > On Wed, 7 Nov 2018 11:18:26 +0100 Michal Hocko <mhocko@kernel.org> wrote: > > > From: Michal Hocko <mhocko@suse.com> > > > > __dump_page prints the mapping pointer but that is quite unhelpful > > for many reports because the pointer itself only helps to distinguish > > anon/ksm mappings from other ones (because of lowest bits > > set). Sometimes it would be much more helpful to know what kind of > > mapping that is actually and if we know this is a file mapping then also > > try to resolve the dentry name. > > > > ... > > > > --- a/mm/debug.c > > +++ b/mm/debug.c > > > > ... > > > > @@ -70,6 +71,18 @@ void __dump_page(struct page *page, const char *reason) > > if (PageCompound(page)) > > pr_cont(" compound_mapcount: %d", compound_mapcount(page)); > > pr_cont("\n"); > > + if (PageAnon(page)) > > + pr_emerg("anon "); > > + else if (PageKsm(page)) > > + pr_emerg("ksm "); > > + else if (mapping) { > > + pr_emerg("%ps ", mapping->a_ops); > > + if (mapping->host->i_dentry.first) { > > + struct dentry *dentry; > > + dentry = container_of(mapping->host->i_dentry.first, struct dentry, d_u.d_alias); > > + pr_emerg("name:\"%*s\" ", dentry->d_name.len, dentry->d_name.name); > > + } > > + } > > There has to be a better way of printing the filename. It is so often > needed. > > The (poorly named and gleefully undocumented) > take_dentry_name_snapshot() looks promising. However it's unclear that > __dump_page() is always called from contexts where > take_dentry_name_snapshot() and release_dentry_name_snapshot() can be > safely called. Probably it's OK, but how to guarantee it? http://lkml.kernel.org/r/20181125080834.GB12455@dhcp22.suse.cz as suggested by Tetsuo?
diff --git a/mm/debug.c b/mm/debug.c index cdacba12e09a..a33177bfc856 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -44,6 +44,7 @@ const struct trace_print_flags vmaflag_names[] = { void __dump_page(struct page *page, const char *reason) { + struct address_space *mapping = page_mapping(page); bool page_poisoned = PagePoisoned(page); int mapcount; @@ -70,6 +71,18 @@ void __dump_page(struct page *page, const char *reason) if (PageCompound(page)) pr_cont(" compound_mapcount: %d", compound_mapcount(page)); pr_cont("\n"); + if (PageAnon(page)) + pr_emerg("anon "); + else if (PageKsm(page)) + pr_emerg("ksm "); + else if (mapping) { + pr_emerg("%ps ", mapping->a_ops); + if (mapping->host->i_dentry.first) { + struct dentry *dentry; + dentry = container_of(mapping->host->i_dentry.first, struct dentry, d_u.d_alias); + pr_emerg("name:\"%*s\" ", dentry->d_name.len, dentry->d_name.name); + } + } BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1); pr_emerg("flags: %#lx(%pGp)\n", page->flags, &page->flags);