diff mbox series

[v3,6/6] fs/proc/kcore: use page_offline_(freeze|thaw)

Message ID 20210526093041.8800-7-david@redhat.com (mailing list archive)
State New, archived
Headers show
Series fs/proc/kcore: don't read offline sections, logically offline pages and hwpoisoned pages | expand

Commit Message

David Hildenbrand May 26, 2021, 9:30 a.m. UTC 
Let's properly synchronize with drivers that set PageOffline().
Unfreeze/thaw every now and then, so drivers that want to set PageOffline()
can make progress.

Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 fs/proc/kcore.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)
diff mbox series

Patch

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 92ff1e4436cb..982e694aae77 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -313,6 +313,7 @@  read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 {
 	char *buf = file->private_data;
 	size_t phdrs_offset, notes_offset, data_offset;
+	size_t page_offline_frozen = 1;
 	size_t phdrs_len, notes_len;
 	struct kcore_list *m;
 	size_t tsz;
@@ -322,6 +323,11 @@  read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 	int ret = 0;
 
 	down_read(&kclist_lock);
+	/*
+	 * Don't race against drivers that set PageOffline() and expect no
+	 * further page access.
+	 */
+	page_offline_freeze();
 
 	get_kcore_size(&nphdr, &phdrs_len, &notes_len, &data_offset);
 	phdrs_offset = sizeof(struct elfhdr);
@@ -480,6 +486,12 @@  read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 			}
 		}
 
+		if (page_offline_frozen++ % MAX_ORDER_NR_PAGES == 0) {
+			page_offline_thaw();
+			cond_resched();
+			page_offline_freeze();
+		}
+
 		if (&m->list == &kclist_head) {
 			if (clear_user(buffer, tsz)) {
 				ret = -EFAULT;
@@ -565,6 +577,7 @@  read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 	}
 
 out:
+	page_offline_thaw();
 	up_read(&kclist_lock);
 	if (ret)
 		return ret;