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Date: Wed, 6 May 2020 17:41:58 -0700
From: Anthony Yznaga <anthony.yznaga@...cle.com>
To: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc: willy@...radead.org, corbet@....net, tglx@...utronix.de,
mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
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kexec@...ts.infradead.org
Subject: [RFC 32/43] shmem: PKRAM: preserve shmem files a chunk at a time
To prepare for multithreading the work done to a preserve a file,
divide the work into subranges of the total index range of the file.
The chunk size is a rather arbitrary 256k indices.
A new API call, pkram_prepare_save_chunk(), is added. It is called
after calling pkram_prepare_save_obj(), and it initializes pkram_stream
with the index range of the next available range of pages to save.
find_get_pages_range() can then be used to get the pages in the range.
When no more index ranges are available, pkram_prepare_save_chunk()
returns -ENODATA.
Signed-off-by: Anthony Yznaga <anthony.yznaga@...cle.com>
---
include/linux/pkram.h | 6 +++++
mm/pkram.c | 26 +++++++++++++++++++++
mm/shmem_pkram.c | 63 +++++++++++++++++++++++++++++++++++----------------
3 files changed, 75 insertions(+), 20 deletions(-)
diff --git a/include/linux/pkram.h b/include/linux/pkram.h
index cbb79d2803c0..e71ccb91d6a6 100644
--- a/include/linux/pkram.h
+++ b/include/linux/pkram.h
@@ -20,6 +20,11 @@ struct pkram_stream {
struct address_space *mapping;
struct mm_struct *mm;
+ unsigned long start_idx; /* first index in range to save */
+ unsigned long end_idx; /* last index in range to save */
+ unsigned long max_idx; /* maximum index to save */
+ atomic64_t *next_idx; /* first index of next range to save */
+
/* byte data */
struct page *data_page;
unsigned int data_offset;
@@ -46,6 +51,7 @@ void pkram_free_pgt_walk_pgd(pgd_t *pgd);
int pkram_prepare_save(struct pkram_stream *ps, const char *name,
gfp_t gfp_mask);
int pkram_prepare_save_obj(struct pkram_stream *ps);
+int pkram_prepare_save_chunk(struct pkram_stream *ps);
void pkram_finish_save(struct pkram_stream *ps);
void pkram_finish_save_obj(struct pkram_stream *ps);
void pkram_discard_save(struct pkram_stream *ps);
diff --git a/mm/pkram.c b/mm/pkram.c
index b83d31740619..5f4e4d12865f 100644
--- a/mm/pkram.c
+++ b/mm/pkram.c
@@ -638,6 +638,25 @@ int pkram_prepare_save(struct pkram_stream *ps, const char *name, gfp_t gfp_mask
return 0;
}
+unsigned long max_pages_per_chunk = 512 * 512;
+
+/*
+ * Initialize the stream @ps for the next index range to save.
+ *
+ * Returns 0 on success, -ENODATA if no index range is available
+ *
+ */
+int pkram_prepare_save_chunk(struct pkram_stream *ps)
+{
+ ps->start_idx = atomic64_fetch_add(max_pages_per_chunk, ps->next_idx);
+ if (ps->start_idx >= ps->max_idx)
+ return -ENODATA;
+
+ ps->end_idx = ps->start_idx + max_pages_per_chunk - 1;
+
+ return 0;
+}
+
/**
* Create a preserved memory object and initialize stream @ps for saving data
* to it.
@@ -667,6 +686,11 @@ int pkram_prepare_save_obj(struct pkram_stream *ps)
obj->obj_pfn = node->obj_pfn;
node->obj_pfn = page_to_pfn(page);
+ ps->next_idx = kmalloc(sizeof(atomic64_t), GFP_KERNEL);
+ if (!ps->next_idx)
+ return -ENOMEM;
+ atomic64_set(ps->next_idx, 0);
+
pkram_stream_init_obj(ps, obj);
return 0;
}
@@ -679,6 +703,8 @@ void pkram_finish_save_obj(struct pkram_stream *ps)
struct pkram_node *node = ps->node;
BUG_ON((node->flags & PKRAM_ACCMODE_MASK) != PKRAM_SAVE);
+
+ kfree(ps->next_idx);
}
/**
diff --git a/mm/shmem_pkram.c b/mm/shmem_pkram.c
index c97d64393822..2f4d0bdf3e05 100644
--- a/mm/shmem_pkram.c
+++ b/mm/shmem_pkram.c
@@ -74,58 +74,81 @@ static int save_page(struct page *page, struct pkram_stream *ps)
return err;
}
-static int save_file_content(struct pkram_stream *ps)
+static int save_file_content_range(struct address_space *mapping,
+ struct pkram_stream *ps)
{
+ unsigned long index, end;
struct pagevec pvec;
- pgoff_t indices[PAGEVEC_SIZE];
- pgoff_t index = 0;
struct page *page;
- int i, err = 0;
+ int err = 0;
+ int i;
+
+ index = ps->start_idx;
+ end = ps->end_idx;
pagevec_init(&pvec);
for ( ; ; ) {
- pvec.nr = find_get_entries(ps->mapping, index, PAGEVEC_SIZE,
- pvec.pages, indices);
+ pvec.nr = find_get_pages_range(mapping, &index, end,
+ PAGEVEC_SIZE, pvec.pages);
if (!pvec.nr)
break;
- for (i = 0; i < pagevec_count(&pvec); i++) {
+ for (i = 0; i < pagevec_count(&pvec); ) {
page = pvec.pages[i];
- index = indices[i];
-
- if (WARN_ON_ONCE(xa_is_value(page))) {
- err = -EINVAL;
- break;
- }
-
lock_page(page);
if (PageTransTail(page)) {
WARN_ONCE(1, "PageTransTail returned true\n");
unlock_page(page);
+ i++;
continue;
}
- BUG_ON(page->mapping != ps->mapping);
+ BUG_ON(page->mapping != mapping);
err = save_page(page, ps);
- i += compound_nr(page) - 1;
- index += compound_nr(page) - 1;
+ if (PageCompound(page)) {
+ index = page->index + compound_nr(page);
+ i += compound_nr(page);
+ } else {
+ i++;
+ }
unlock_page(page);
if (err)
break;
}
- pagevec_remove_exceptionals(&pvec);
pagevec_release(&pvec);
- if (err)
+ if (err || (index > end))
break;
cond_resched();
- index++;
}
return err;
}
+static int do_save_file_content(struct pkram_stream *ps)
+{
+ int ret;
+
+ do {
+ ret = pkram_prepare_save_chunk(ps);
+ if (!ret)
+ ret = save_file_content_range(ps->mapping, ps);
+ } while (!ret);
+
+ if (ret == -ENODATA)
+ ret = 0;
+
+ return ret;
+}
+
+static int save_file_content(struct pkram_stream *ps)
+{
+ ps->max_idx = DIV_ROUND_UP(i_size_read(ps->mapping->host), PAGE_SIZE);
+
+ return do_save_file_content(ps);
+}
+
static int save_file(struct dentry *dentry, struct pkram_stream *ps)
{
struct inode *inode = dentry->d_inode;
--
2.13.3
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