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Subject[f2fs-dev] [PATCH] f2fs:fix truncate_partial_nodes bug
truncate_partial_nodes puts pages incorrectly in two cases.note that the value for argc 'depth' can only be 2 or 3(see truncate_inode_blocks --->truncate_partial_nodes ).
first case:err happened in the first 'for' loop
assume depth is 2,when err happened,pages[0] is invalid,so this page don't need to be put when func return,there is no problem.
but when depth is 3 ,pages isn't put correctly when pages[0] is valid and pages[1] is invalid.in this case,depth is set to 2(ref to statemnt depth = i + 1) ,and then 'goto fail'.
in label 'fail', for (i = depth - 3; i >= 0; i--) cann't meet the condition because i=-1,so pages[0] cann't be put when func return.
second case:err happened in the second 'for' loop
now,we've got pages[0] with argc 'depth' is 2 ,or we've got pages[0] and pages[1] with depth is 3.when err happend,we need 'goto fail' to put pages we've got.
when depth is 2,in label 'fail',for (i = depth - 3; i >= 0; i--) cann't meet the condition because i=-1,so pages[0] cann't be put.
when depth is 3,in label 'fail',for (i = depth - 3; i >= 0; i--) can only put pages[0],pages[1] also cann't be put.
notes 'depth' has been changed before first 'goto fail'(ref to statemnt depth = i + 1),so pass this modified 'depth' to trace_f2fs_truncate_partial_nodes is also incorrectly.

From 9de8efa31759ce86a032f5ad092d337b686ede06 Mon Sep 17 00:00:00 2001
Signed-off-by: Shifei Ge <shifei10.ge@samsung.com>
---
fs/f2fs/node.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 304d5ce..9986930 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -625,6 +625,7 @@ static int truncate_partial_nodes(struct dnode_of_data *dn,
int err = 0;
int i;
int idx = depth - 2;
+ int dep = depth;

nid[0] = le32_to_cpu(ri->i_nid[offset[0] - NODE_DIR1_BLOCK]);
if (!nid[0])
@@ -663,11 +664,12 @@ static int truncate_partial_nodes(struct dnode_of_data *dn,
}
offset[idx]++;
offset[depth - 1] = 0;
+ depth--;
fail:
- for (i = depth - 3; i >= 0; i--)
+ for (i = depth - 2; i >= 0; i--)
f2fs_put_page(pages[i], 1);

- trace_f2fs_truncate_partial_nodes(dn->inode, nid, depth, err);
+ trace_f2fs_truncate_partial_nodes(dn->inode, nid, dep, err);

return err;
}
--
1.7.9.5
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