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Subject[PATCH v2 6/6] fs/proc/kcore: use page_offline_(freeze|thaw)
Date
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.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
fs/proc/kcore.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

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;
--
2.31.1
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