[V5] ocfs2: fix crash on ocfs2_duplicate_clusters_by_page
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Message ID 20180830075041.14879-1-lchen@suse.com
State New
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Series
  • [V5] ocfs2: fix crash on ocfs2_duplicate_clusters_by_page
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Commit Message

Larry Chen Aug. 30, 2018, 7:50 a.m. UTC
ocfs2_duplicate_clusters_by_page may crash if one of extent's pages is dirty.
When a page has not been written back, it is still in dirty state. If
ocfs2_duplicate_clusters_by_page is called against the
dirty page, the crash happens.

To fix this bug, we can write back the page rather than just wait.

The following is the back trace dump:

kernel BUG at /root/code/ocfs2/refcounttree.c:2961! 
	BUG_ON(PageDirty(page));
[exception RIP: ocfs2_duplicate_clusters_by_page+822]
__ocfs2_move_extent+0x80/0x450 [ocfs2]
? __ocfs2_claim_clusters+0x130/0x250 [ocfs2]
ocfs2_defrag_extent+0x5b8/0x5e0 [ocfs2]
__ocfs2_move_extents_range+0x2a4/0x470 [ocfs2]
ocfs2_move_extents+0x180/0x3b0 [ocfs2]
? ocfs2_wait_for_recovery+0x13/0x70 [ocfs2]
ocfs2_ioctl_move_extents+0x133/0x2d0 [ocfs2]
ocfs2_ioctl+0x253/0x640 [ocfs2]
do_vfs_ioctl+0x90/0x5f0
SyS_ioctl+0x74/0x80
do_syscall_64+0x74/0x140
entry_SYSCALL_64_after_hwframe+0x3d/0xa2


Change-log:
1. Once we find the page is dirty, we do not wait until it's clean,
   but rather we use write_one_page to write it back

2. write_one_page arguments list changed, adjust and retest this patch. 

3. Comments has been changed

4. Sorry, miss "ocfs2" prefix in patch title

Signed-off-by: Larry Chen <lchen@suse.com>
---
 fs/ocfs2/refcounttree.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

Comments

Changwei Ge Aug. 30, 2018, 7:55 a.m. UTC | #1
Looks good to me.


On 2018/8/30 15:50, Larry Chen wrote:
> ocfs2_duplicate_clusters_by_page may crash if one of extent's pages is dirty.
> When a page has not been written back, it is still in dirty state. If
> ocfs2_duplicate_clusters_by_page is called against the
> dirty page, the crash happens.
>
> To fix this bug, we can write back the page rather than just wait.
>
> The following is the back trace dump:
>
> kernel BUG at /root/code/ocfs2/refcounttree.c:2961!
> 	BUG_ON(PageDirty(page));
> [exception RIP: ocfs2_duplicate_clusters_by_page+822]
> __ocfs2_move_extent+0x80/0x450 [ocfs2]
> ? __ocfs2_claim_clusters+0x130/0x250 [ocfs2]
> ocfs2_defrag_extent+0x5b8/0x5e0 [ocfs2]
> __ocfs2_move_extents_range+0x2a4/0x470 [ocfs2]
> ocfs2_move_extents+0x180/0x3b0 [ocfs2]
> ? ocfs2_wait_for_recovery+0x13/0x70 [ocfs2]
> ocfs2_ioctl_move_extents+0x133/0x2d0 [ocfs2]
> ocfs2_ioctl+0x253/0x640 [ocfs2]
> do_vfs_ioctl+0x90/0x5f0
> SyS_ioctl+0x74/0x80
> do_syscall_64+0x74/0x140
> entry_SYSCALL_64_after_hwframe+0x3d/0xa2
>
>
> Change-log:
> 1. Once we find the page is dirty, we do not wait until it's clean,
>     but rather we use write_one_page to write it back
>
> 2. write_one_page arguments list changed, adjust and retest this patch.
>
> 3. Comments has been changed
>
> 4. Sorry, miss "ocfs2" prefix in patch title
>
> Signed-off-by: Larry Chen <lchen@suse.com>
Acked-by: Changwei Ge <ge.changwei@h3c.com>

> ---
>   fs/ocfs2/refcounttree.c | 16 ++++++++++++----
>   1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c
> index 7869622af22a..ed84d05c7d00 100644
> --- a/fs/ocfs2/refcounttree.c
> +++ b/fs/ocfs2/refcounttree.c
> @@ -2946,6 +2946,7 @@ int ocfs2_duplicate_clusters_by_page(handle_t *handle,
>   		if (map_end & (PAGE_SIZE - 1))
>   			to = map_end & (PAGE_SIZE - 1);
>   
> +retry:
>   		page = find_or_create_page(mapping, page_index, GFP_NOFS);
>   		if (!page) {
>   			ret = -ENOMEM;
> @@ -2954,11 +2955,18 @@ int ocfs2_duplicate_clusters_by_page(handle_t *handle,
>   		}
>   
>   		/*
> -		 * In case PAGE_SIZE <= CLUSTER_SIZE, This page
> -		 * can't be dirtied before we CoW it out.
> +		 * In case PAGE_SIZE <= CLUSTER_SIZE, we do not expect a dirty page,
> +		 * so write it back.
>   		 */
> -		if (PAGE_SIZE <= OCFS2_SB(sb)->s_clustersize)
> -			BUG_ON(PageDirty(page));
> +		if (PAGE_SIZE <= OCFS2_SB(sb)->s_clustersize) {
> +			if (PageDirty(page)) {
> +				/*
> +				 * write_on_page will unlock the page on return
> +				 */
> +				ret = write_one_page(page);
> +				goto retry;
> +			}
> +		}
>   
>   		if (!PageUptodate(page)) {
>   			ret = block_read_full_page(page, ocfs2_get_block);

Patch
diff mbox series

diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c
index 7869622af22a..ed84d05c7d00 100644
--- a/fs/ocfs2/refcounttree.c
+++ b/fs/ocfs2/refcounttree.c
@@ -2946,6 +2946,7 @@  int ocfs2_duplicate_clusters_by_page(handle_t *handle,
 		if (map_end & (PAGE_SIZE - 1))
 			to = map_end & (PAGE_SIZE - 1);
 
+retry:
 		page = find_or_create_page(mapping, page_index, GFP_NOFS);
 		if (!page) {
 			ret = -ENOMEM;
@@ -2954,11 +2955,18 @@  int ocfs2_duplicate_clusters_by_page(handle_t *handle,
 		}
 
 		/*
-		 * In case PAGE_SIZE <= CLUSTER_SIZE, This page
-		 * can't be dirtied before we CoW it out.
+		 * In case PAGE_SIZE <= CLUSTER_SIZE, we do not expect a dirty page,
+		 * so write it back.
 		 */
-		if (PAGE_SIZE <= OCFS2_SB(sb)->s_clustersize)
-			BUG_ON(PageDirty(page));
+		if (PAGE_SIZE <= OCFS2_SB(sb)->s_clustersize) {
+			if (PageDirty(page)) {
+				/*
+				 * write_on_page will unlock the page on return
+				 */
+				ret = write_one_page(page);
+				goto retry;
+			}
+		}
 
 		if (!PageUptodate(page)) {
 			ret = block_read_full_page(page, ocfs2_get_block);