Messages in this thread Patch in this message | | | From | Ingo Molnar <> | Subject | [PATCH 02/12] x86/mm/hotplug: Remove pgd_list use from the memory hotplug code | Date | Sat, 13 Jun 2015 11:49:05 +0200 |
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The memory hotplug code uses sync_global_pgds() to synchronize updates to the global (&init_mm) kernel PGD and the task PGDs. It does this by iterating over the pgd_list - which list closely tracks task creation/destruction via fork/clone.
But we want to remove this list, so that it does not have to be maintained from fork()/exit(), so convert the memory hotplug code to use the task list to iterate over all pgds in the system.
Also improve the comments a bit, to make this function easier to understand.
Only lightly tested, as I don't have a memory hotplug setup.
Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Waiman Long <Waiman.Long@hp.com> Cc: linux-mm@kvack.org Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/mm/init_64.c | 38 +++++++++++++++++++++++++------------- 1 file changed, 25 insertions(+), 13 deletions(-)
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 3fba623e3ba5..527d5d4d020c 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -160,8 +160,8 @@ static int __init nonx32_setup(char *str) __setup("noexec32=", nonx32_setup); /* - * When memory was added/removed make sure all the processes MM have - * suitable PGD entries in the local PGD level page. + * When memory was added/removed make sure all the process MMs have + * matching PGD entries in the local PGD level page as well. */ void sync_global_pgds(unsigned long start, unsigned long end, int removed) { @@ -169,29 +169,40 @@ void sync_global_pgds(unsigned long start, unsigned long end, int removed) for (address = start; address <= end; address += PGDIR_SIZE) { const pgd_t *pgd_ref = pgd_offset_k(address); - struct page *page; + struct task_struct *g, *p; /* - * When it is called after memory hot remove, pgd_none() - * returns true. In this case (removed == 1), we must clear - * the PGD entries in the local PGD level page. + * When this function is called after memory hot remove, + * pgd_none() already returns true, but only the reference + * kernel PGD has been cleared, not the process PGDs. + * + * So clear the affected entries in every process PGD as well: */ if (pgd_none(*pgd_ref) && !removed) continue; - spin_lock(&pgd_lock); - list_for_each_entry(page, &pgd_list, lru) { + spin_lock(&pgd_lock); /* Implies rcu_read_lock() for the task list iteration: */ + + for_each_process_thread(g, p) { + struct mm_struct *mm; pgd_t *pgd; spinlock_t *pgt_lock; - pgd = (pgd_t *)page_address(page) + pgd_index(address); - /* the pgt_lock only for Xen */ - pgt_lock = &pgd_page_get_mm(page)->page_table_lock; + task_lock(p); + mm = p->mm; + if (!mm) { + task_unlock(p); + continue; + } + + pgd = mm->pgd; + + /* The pgt_lock is only used by Xen: */ + pgt_lock = &mm->page_table_lock; spin_lock(pgt_lock); if (!pgd_none(*pgd_ref) && !pgd_none(*pgd)) - BUG_ON(pgd_page_vaddr(*pgd) - != pgd_page_vaddr(*pgd_ref)); + BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref)); if (removed) { if (pgd_none(*pgd_ref) && !pgd_none(*pgd)) @@ -202,6 +213,7 @@ void sync_global_pgds(unsigned long start, unsigned long end, int removed) } spin_unlock(pgt_lock); + task_unlock(p); } spin_unlock(&pgd_lock); } -- 2.1.4
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