fs/proc/kcore: use page_offline_(freeze|thaw)

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.

Link: https://lkml.kernel.org/r/20210526093041.8800-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Aili Yao <yaoaili@kingsoft.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jiri Bohac <jbohac@suse.cz>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: Steven Price <steven.price@arm.com>
Cc: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 92ff1e4436cb91f6053d9625629c04301b779973..982e694aae77dec9d4a132764708c4e913dd6d43 100644 (file)
--- 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 @@ skip:
        }
 
 out:
+       page_offline_thaw();
        up_read(&kclist_lock);
        if (ret)
                return ret;