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authorJan Kara <jack@suse.cz>2012-09-27 07:11:13 +0400
committerTheodore Ts'o <tytso@mit.edu>2012-09-27 07:11:13 +0400
commitb794e7a6ebfbddb819b0e75ab59ada6b08a285f2 (patch)
tree4ae2983a324f3788b831190c30cf92117e76e3d8 /fs/jbd2/commit.c
parent9b68733273665a4c0d98041a657dabfb4fd6bd80 (diff)
downloadlinux-b794e7a6ebfbddb819b0e75ab59ada6b08a285f2.tar.xz
jbd2: fix assertion failure in commit code due to lacking transaction credits
ext4 users of data=journal mode with blocksize < pagesize were occasionally hitting assertion failure in jbd2_journal_commit_transaction() checking whether the transaction has at least as many credits reserved as buffers attached. The core of the problem is that when a file gets truncated, buffers that still need checkpointing or that are attached to the committing transaction are left with buffer_mapped set. When this happens to buffers beyond i_size attached to a page stradding i_size, subsequent write extending the file will see these buffers and as they are mapped (but underlying blocks were freed) things go awry from here. The assertion failure just coincidentally (and in this case luckily as we would start corrupting filesystem) triggers due to journal_head not being properly cleaned up as well. We fix the problem by unmapping buffers if possible (in lots of cases we just need a buffer attached to a transaction as a place holder but it must not be written out anyway). And in one case, we just have to bite the bullet and wait for transaction commit to finish. CC: Josef Bacik <jbacik@fusionio.com> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/jbd2/commit.c')
-rw-r--r--fs/jbd2/commit.c40
1 files changed, 29 insertions, 11 deletions
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index af5280fb579b..3091d42992f0 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -1014,17 +1014,35 @@ restart_loop:
* there's no point in keeping a checkpoint record for
* it. */
- /* A buffer which has been freed while still being
- * journaled by a previous transaction may end up still
- * being dirty here, but we want to avoid writing back
- * that buffer in the future after the "add to orphan"
- * operation been committed, That's not only a performance
- * gain, it also stops aliasing problems if the buffer is
- * left behind for writeback and gets reallocated for another
- * use in a different page. */
- if (buffer_freed(bh) && !jh->b_next_transaction) {
- clear_buffer_freed(bh);
- clear_buffer_jbddirty(bh);
+ /*
+ * A buffer which has been freed while still being journaled by
+ * a previous transaction.
+ */
+ if (buffer_freed(bh)) {
+ /*
+ * If the running transaction is the one containing
+ * "add to orphan" operation (b_next_transaction !=
+ * NULL), we have to wait for that transaction to
+ * commit before we can really get rid of the buffer.
+ * So just clear b_modified to not confuse transaction
+ * credit accounting and refile the buffer to
+ * BJ_Forget of the running transaction. If the just
+ * committed transaction contains "add to orphan"
+ * operation, we can completely invalidate the buffer
+ * now. We are rather through in that since the
+ * buffer may be still accessible when blocksize <
+ * pagesize and it is attached to the last partial
+ * page.
+ */
+ jh->b_modified = 0;
+ if (!jh->b_next_transaction) {
+ clear_buffer_freed(bh);
+ clear_buffer_jbddirty(bh);
+ clear_buffer_mapped(bh);
+ clear_buffer_new(bh);
+ clear_buffer_req(bh);
+ bh->b_bdev = NULL;
+ }
}
if (buffer_jbddirty(bh)) {