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authordingdinghua <dingdinghua85@gmail.com>2009-07-13 17:55:35 -0400
committerTheodore Ts'o <tytso@mit.edu>2009-07-13 17:55:35 -0400
commit96577c43827697ca1af5982fa256a34786d0c720 (patch)
treeaa752d4685f5702976683401dadb7557f161d62d
parent833576b362e15c38be3bfe43942cda693e56287c (diff)
downloadlinux-2.6.34-ux500-96577c43827697ca1af5982fa256a34786d0c720.tar.gz
jbd2: fix race between write_metadata_buffer and get_write_access
The function jbd2_journal_write_metadata_buffer() calls jbd_unlock_bh_state(bh_in) too early; this could potentially allow another thread to call get_write_access on the buffer head, modify the data, and dirty it, and allowing the wrong data to be written into the journal. Fortunately, if we lose this race, the only time this will actually cause filesystem corruption is if there is a system crash or other unclean shutdown of the system before the next commit can take place. Signed-off-by: dingdinghua <dingdinghua85@gmail.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
-rw-r--r--fs/jbd2/journal.c20
1 files changed, 11 insertions, 9 deletions
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 7b545c3b394..e378cb38397 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -297,6 +297,7 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
unsigned int new_offset;
struct buffer_head *bh_in = jh2bh(jh_in);
struct jbd2_buffer_trigger_type *triggers;
+ journal_t *journal = transaction->t_journal;
/*
* The buffer really shouldn't be locked: only the current committing
@@ -310,6 +311,11 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
J_ASSERT_BH(bh_in, buffer_jbddirty(bh_in));
new_bh = alloc_buffer_head(GFP_NOFS|__GFP_NOFAIL);
+ /* keep subsequent assertions sane */
+ new_bh->b_state = 0;
+ init_buffer(new_bh, NULL, NULL);
+ atomic_set(&new_bh->b_count, 1);
+ new_jh = jbd2_journal_add_journal_head(new_bh); /* This sleeps */
/*
* If a new transaction has already done a buffer copy-out, then
@@ -388,14 +394,6 @@ repeat:
kunmap_atomic(mapped_data, KM_USER0);
}
- /* keep subsequent assertions sane */
- new_bh->b_state = 0;
- init_buffer(new_bh, NULL, NULL);
- atomic_set(&new_bh->b_count, 1);
- jbd_unlock_bh_state(bh_in);
-
- new_jh = jbd2_journal_add_journal_head(new_bh); /* This sleeps */
-
set_bh_page(new_bh, new_page, new_offset);
new_jh->b_transaction = NULL;
new_bh->b_size = jh2bh(jh_in)->b_size;
@@ -412,7 +410,11 @@ repeat:
* copying is moved to the transaction's shadow queue.
*/
JBUFFER_TRACE(jh_in, "file as BJ_Shadow");
- jbd2_journal_file_buffer(jh_in, transaction, BJ_Shadow);
+ spin_lock(&journal->j_list_lock);
+ __jbd2_journal_file_buffer(jh_in, transaction, BJ_Shadow);
+ spin_unlock(&journal->j_list_lock);
+ jbd_unlock_bh_state(bh_in);
+
JBUFFER_TRACE(new_jh, "file as BJ_IO");
jbd2_journal_file_buffer(new_jh, transaction, BJ_IO);