[PATCH v1 7/7] fs/proc/kcore: use page_offline_(freeze|unfreeze)
From: David Hildenbrand <hidden>
Date: 2021-04-29 12:27:32
Also in:
linux-hyperv, linux-mm, lkml, virtualization
Subsystem:
filesystems (vfs and infrastructure), kcore, proc filesystem, the rest · Maintainers:
Alexander Viro, Christian Brauner, Omar Sandoval, Linus Torvalds
Let's properly synchronize with drivers that set PageOffline(). Unfreeze every now and then, so drivers that want to set PageOffline() can make progress. Signed-off-by: David Hildenbrand <redacted> --- fs/proc/kcore.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 92ff1e4436cb..3d7531f47389 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c@@ -311,6 +311,7 @@ static void append_kcore_note(char *notes, size_t *i, const char *name, static ssize_t read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) { + size_t page_offline_frozen = 0; char *buf = file->private_data; size_t phdrs_offset, notes_offset, data_offset; size_t phdrs_len, notes_len;
@@ -509,6 +510,18 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) pfn = __pa(start) >> PAGE_SHIFT; page = pfn_to_online_page(pfn); + /* + * Don't race against drivers that set PageOffline() + * and expect no further page access. + */ + if (page_offline_frozen == MAX_ORDER_NR_PAGES) { + page_offline_unfreeze(); + page_offline_frozen = 0; + cond_resched(); + } + if (!page_offline_frozen++) + page_offline_freeze(); + /* * Don't read offline sections, logically offline pages * (e.g., inflated in a balloon), hwpoisoned pages,
@@ -565,6 +578,8 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) } out: + if (page_offline_frozen) + page_offline_unfreeze(); up_read(&kclist_lock); if (ret) return ret;
--
2.30.2