From: Hidehiro Kawai <hidehiro.kawai.ez@xxxxxxxxxxx>
A transient I/O error can corrupt inode data. Here is the scenario:
(1) update inode_A at the block_B
(2) pdflush writes out new inode_A to the filesystem, but it results
in write I/O error, at this point, BH_Uptodate flag of the buffer
for block_B is cleared and BH_Write_EIO is set
(3) create new inode_C which located at block_B, and
__ext4_get_inode_loc() tries to read on-disk block_B because the
buffer is not uptodate
(4) if it can read on-disk block_B successfully, inode_A is
overwritten by old data
This patch makes __ext4_get_inode_loc() not read the inode block if the
buffer has BH_Write_EIO flag. In this case, the buffer should have the
latest information, so setting the uptodate flag to the buffer (this
avoids WARN_ON_ONCE() in mark_buffer_dirty().)
According to this change, we would need to test BH_Write_EIO flag for the
error checking. Currently nobody checks write I/O errors on metadata
buffers, but it will be done in other patches I'm working on.
Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@xxxxxxxxxxx>
Cc: sugita <yumiko.sugita.yf@xxxxxxxxxxx>
Cc: Satoshi OSHIMA <satoshi.oshima.fk@xxxxxxxxxxx>
Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxx>
Cc: <linux-ext4@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
---
fs/ext4/inode.c | 10 ++++++++++
1 files changed, 10 insertions(+), 0 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 33f1ed4..5262589 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3610,6 +3610,16 @@ static int __ext4_get_inode_loc(struct inode *inode,
}
if (!buffer_uptodate(bh)) {
lock_buffer(bh);
+
+ /*
+ * If the buffer has the write error flag, we have failed
+ * to write out another inode in the same block. In this
+ * case, we don't have to read the block because we may
+ * read the old inode data successfully.
+ */
+ if (buffer_write_io_error(bh) && !buffer_uptodate(bh))
+ set_buffer_uptodate(bh);
+
if (buffer_uptodate(bh)) {
/* someone brought it uptodate while we waited */
unlock_buffer(bh);
--
1.5.6.1.205.ge2c7.dirty
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