/usr/src/kernel-patches/lustre/patches/jbd-check-for-unmapped-buffer.patch is in linux-patch-lustre 1.8.5+dfsg-3ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 | Date: Mon, 23 Oct 2006 15:40:48 -0500
From: Eric Sandeen <sandeen@redhat.com>
Subject: [PATCH RHEL5] handle races w/ truncate in journal_dirty_data()
This is for BZ 209647 <https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=209647>: ext3/jbd panic
This patch is now in -mm.
When running several fsx's and other filesystem stress tests, we found
cases where an unmapped buffer was still being sent to submit_bh by the
ext3 dirty data journaling code.
I saw this happen in two ways, both related to another thread doing a
truncate which would unmap the buffer in question.
Either we would get into journal_dirty_data with a bh which was already
unmapped (although journal_dirty_data_fn had checked for this earlier, the
state was not locked at that point), or it would get unmapped in the middle
of journal_dirty_data when we dropped locks to call sync_dirty_buffer.
By re-checking for mapped state after we've acquired the bh state lock, we
should avoid these races. If we find a buffer which is no longer mapped,
we essentially ignore it, because journal_unmap_buffer has already decided
that this buffer can go away.
I've also added tracepoints in these two cases, and made a couple other
tracepoint changes that I found useful in debugging this.
Signed-off-by: Eric Sandeen <esandeen@redhat.com>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
fs/jbd/transaction.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
Index: linux-2.6.18-1.2732.el5/fs/jbd/transaction.c
===================================================================
--- linux-2.6.18-1.2732.el5.orig/fs/jbd/transaction.c
+++ linux-2.6.18-1.2732.el5/fs/jbd/transaction.c
@@ -967,6 +967,13 @@ int journal_dirty_data(handle_t *handle,
*/
jbd_lock_bh_state(bh);
spin_lock(&journal->j_list_lock);
+
+ /* Now that we have bh_state locked, are we really still mapped? */
+ if (!buffer_mapped(bh)) {
+ JBUFFER_TRACE(jh, "unmapped buffer, bailing out");
+ goto no_journal;
+ }
+
if (jh->b_transaction) {
JBUFFER_TRACE(jh, "has transaction");
if (jh->b_transaction != handle->h_transaction) {
@@ -1028,6 +1035,11 @@ int journal_dirty_data(handle_t *handle,
sync_dirty_buffer(bh);
jbd_lock_bh_state(bh);
spin_lock(&journal->j_list_lock);
+ /* Since we dropped the lock... */
+ if (!buffer_mapped(bh)) {
+ JBUFFER_TRACE(jh, "buffer got unmapped");
+ goto no_journal;
+ }
/* The buffer may become locked again at any
time if it is redirtied */
}
@@ -1823,6 +1835,7 @@ static int journal_unmap_buffer(journal_
}
}
} else if (transaction == journal->j_committing_transaction) {
+ JBUFFER_TRACE(jh, "on committing transaction");
if (jh->b_jlist == BJ_Locked) {
/*
* The buffer is on the committing transaction's locked
@@ -1837,7 +1850,6 @@ static int journal_unmap_buffer(journal_
* can remove it's next_transaction pointer from the
* running transaction if that is set, but nothing
* else. */
- JBUFFER_TRACE(jh, "on committing transaction");
set_buffer_freed(bh);
if (jh->b_next_transaction) {
J_ASSERT(jh->b_next_transaction ==
@@ -1857,6 +1869,7 @@ static int journal_unmap_buffer(journal_
* i_size already for this truncate so recovery will not
* expose the disk blocks we are discarding here.) */
J_ASSERT_JH(jh, transaction == journal->j_running_transaction);
+ JBUFFER_TRACE(jh, "on running transaction");
may_free = __dispose_buffer(jh, transaction);
}
|