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Date: Mon, 12 Oct 2015 14:00:04 -0700
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: Chao Yu <chao2.yu@...sung.com>
Cc: linux-f2fs-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs crypto: fix racing of accessing encrypted page
among different competitors
On Thu, Oct 08, 2015 at 08:50:39PM +0800, Chao Yu wrote:
> >From 0211c6ed82440891b3369851d079f6c69b432b6c Mon Sep 17 00:00:00 2001
> From: Chao Yu <chao2.yu@...sung.com>
> Date: Thu, 8 Oct 2015 13:27:34 +0800
> Subject: [PATCH] f2fs crypto: fix racing of accessing encrypted page among
> different competitors
>
> 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@...sung.com>
> ---
> 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;
Let's remain just to make sure.
> 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);
Why 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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