[PATCH] f2fs crypto: fix racing of accessing encrypted page among different competitors

[Chao Yu]

Since we use different page cache (normally inode's page cache for R/W
and meta inode's page cache for GC) to cache the same physical block
which is belong to an encrypted inode. Writeback of these two page
cache should be exclusive, but now we didn't handle writeback state
well, so there may be potential racing problem:

a)
kworker:				f2fs_gc:
 - f2fs_write_data_pages
  - f2fs_write_data_page
   - do_write_data_page
    - write_data_page
     - f2fs_submit_page_mbio
(page#1 in inode's page cache was queued
in f2fs bio cache, and be ready to write
to new blkaddr)
					 - gc_data_segment
					  - move_encrypted_block
					   - pagecache_get_page
					(page#2 in meta inode's page cache
					was cached with the invalid datas
					of physical block located in new
					blkaddr)
					   - f2fs_submit_page_mbio
					(page#1 was submitted, later, page#2
					with invalid data will be submitted)

b)
f2fs_gc:
 - gc_data_segment
  - move_encrypted_block
   - f2fs_submit_page_mbio
(page#1 in meta inode's page cache was
queued in f2fs bio cache, and be ready
to write to new blkaddr)
					user thread:
					 - f2fs_write_begin
					  - f2fs_submit_page_bio
					(we submit the request to block layer
					to update page#2 in inode's page cache
					with physical block located in new
					blkaddr, so here we may read gabbage
					data from new blkaddr since GC hasn't
					writebacked the page#1 yet)

This patch fixes above potential racing problem for encrypted inode.

Signed-off-by: Chao Yu <chao2.yu@xxxxxxxxxxx>
---
 fs/f2fs/data.c    | 20 +++++++++++---------
 fs/f2fs/f2fs.h    |  1 +
 fs/f2fs/file.c    |  5 +++++
 fs/f2fs/gc.c      | 13 ++++++++++---
 fs/f2fs/segment.c | 17 +++++++++++++++++
 5 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 40a0102..d791bd3 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -954,21 +954,14 @@ submit_and_realloc:
 
 			if (f2fs_encrypted_inode(inode) &&
 					S_ISREG(inode->i_mode)) {
-				struct page *cpage;
 
 				ctx = f2fs_get_crypto_ctx(inode);
 				if (IS_ERR(ctx))
 					goto set_error_page;
 
 				/* wait the page to be moved by cleaning */
-				cpage = find_lock_page(
-						META_MAPPING(F2FS_I_SB(inode)),
-						block_nr);
-				if (cpage) {
-					f2fs_wait_on_page_writeback(cpage,
-									DATA);
-					f2fs_put_page(cpage, 1);
-				}
+				f2fs_wait_on_encrypted_page_writeback(
+						F2FS_I_SB(inode), block_nr);
 			}
 
 			bio = bio_alloc(GFP_KERNEL,
@@ -1059,6 +1052,11 @@ int do_write_data_page(struct f2fs_io_info *fio)
 	}
 
 	if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode)) {
+
+		/* wait for GCed encrypted page writeback */
+		f2fs_wait_on_encrypted_page_writeback(F2FS_I_SB(inode),
+							fio->blk_addr);
+
 		fio->encrypted_page = f2fs_encrypt(inode, fio->page);
 		if (IS_ERR(fio->encrypted_page)) {
 			err = PTR_ERR(fio->encrypted_page);
@@ -1446,6 +1444,10 @@ put_next:
 
 	f2fs_wait_on_page_writeback(page, DATA);
 
+	/* wait for GCed encrypted page writeback */
+	if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
+		f2fs_wait_on_encrypted_page_writeback(sbi, dn.data_blkaddr);
+
 	if (len == PAGE_CACHE_SIZE)
 		goto out_update;
 	if (PageUptodate(page))
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index a7522a4..dc4d30b 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1778,6 +1778,7 @@ void f2fs_replace_block(struct f2fs_sb_info *, struct dnode_of_data *,
 void allocate_data_block(struct f2fs_sb_info *, struct page *,
 		block_t, block_t *, struct f2fs_summary *, int);
 void f2fs_wait_on_page_writeback(struct page *, enum page_type);
+void f2fs_wait_on_encrypted_page_writeback(struct f2fs_sb_info *, block_t);
 void write_data_summaries(struct f2fs_sb_info *, block_t);
 void write_node_summaries(struct f2fs_sb_info *, block_t);
 int lookup_journal_in_cursum(struct f2fs_summary_block *,
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index e2d9910..1d2df88 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -87,6 +87,11 @@ static int f2fs_vm_page_mkwrite(struct vm_area_struct *vma,
 mapped:
 	/* fill the page */
 	f2fs_wait_on_page_writeback(page, DATA);
+
+	/* wait for GCed encrypted page writeback */
+	if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
+		f2fs_wait_on_encrypted_page_writeback(sbi, dn.data_blkaddr);
+
 	/* if gced page is attached, don't write to cold segment */
 	clear_cold_data(page);
 out:
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index e7cec86..2493fd6 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -559,14 +559,21 @@ static void move_encrypted_block(struct inode *inode, block_t bidx)
 	if (err)
 		goto out;
 
-	if (unlikely(dn.data_blkaddr == NULL_ADDR))
+	if (unlikely(dn.data_blkaddr == NULL_ADDR)) {
+		ClearPageUptodate(page);
 		goto put_out;
+	}
+
+	/*
+	 * don't cache encrypted data into meta inode until previous dirty
+	 * data were writebacked to avoid racing between GC and flush.
+	 */
+	f2fs_wait_on_page_writeback(page, DATA);
 
 	get_node_info(fio.sbi, dn.nid, &ni);
 	set_summary(&sum, dn.nid, dn.ofs_in_node, ni.version);
 
 	/* read page */
-	fio.page = page;
 	fio.blk_addr = dn.data_blkaddr;
 
 	fio.encrypted_page = pagecache_get_page(META_MAPPING(fio.sbi),
@@ -589,7 +596,7 @@ static void move_encrypted_block(struct inode *inode, block_t bidx)
 		goto put_page_out;
 
 	set_page_dirty(fio.encrypted_page);
-	f2fs_wait_on_page_writeback(fio.encrypted_page, META);
+	f2fs_wait_on_page_writeback(fio.encrypted_page, DATA);
 	if (clear_page_dirty_for_io(fio.encrypted_page))
 		dec_page_count(fio.sbi, F2FS_DIRTY_META);
 
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 3c546eb..d5d760c 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1462,6 +1462,23 @@ void f2fs_wait_on_page_writeback(struct page *page,
 	}
 }
 
+void f2fs_wait_on_encrypted_page_writeback(struct f2fs_sb_info *sbi,
+							block_t blkaddr)
+{
+	struct page *cpage;
+
+	if (blkaddr == NEW_ADDR)
+		return;
+
+	f2fs_bug_on(sbi, blkaddr == NULL_ADDR);
+
+	cpage = find_lock_page(META_MAPPING(sbi), blkaddr);
+	if (cpage) {
+		f2fs_wait_on_page_writeback(cpage, DATA);
+		f2fs_put_page(cpage, 1);
+	}
+}
+
 static int read_compacted_summaries(struct f2fs_sb_info *sbi)
 {
 	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
-- 
2.5.2


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