[PATCH-2.4] [RESEND] Fix deadlock in journal_create

From: Mark Fasheh (mark.fasheh@oracle.com)
Date: Fri Jul 18 2003 - 16:54:22 EST

        I sent this initially against 2.4.21-rc6 and it didn't make it in
 -- even though it got Stephen's OK. Here's a resend -- I've identified that
the bug still exists and 2.4.22-pre7. The patch didn't need to be changed as
it still applies cleanly.

        I ran across a deadlock when trying to do a journal_create
at mount time. The problem is that journal_create does a sync_dev which
eventually tries to do a get_super which does:


The problem arises if I call journal_create from my read_super method in
which case get_sb_bdev has already done:


from alloc_super. Replacing the sync_dev call with an fsync_no_super seems
to have fixed the deadlock.

It you want to test this out using ext3 (I have verified it with my own
filesystem), simply follow these steps:
1) create an ext2 filesystem on a device
2) mount that new partition and make a "journal file" on it (using dd).
get the inode number of that file.
3) unmount it and remount it as an ext3 filesystem using the option:
journal=inode_number where inode number is the inode number of the journal
file you just created.
This will get ext3's read_super method to call ext3_create_journal which
will hang during a journal_create.

A trivial patch to fix this is attached.

Mark Fasheh
Software Developer, Oracle Corp

--- linux-2.4.22-pre7/fs/jbd/journal.c.orig 2003-05-30 11:49:10.000000000 -0700 +++ linux-2.4.22-pre7/fs/jbd/journal.c 2003-05-30 11:49:18.000000000 -0700 @@ -912,7 +912,7 @@ int journal_create(journal_t *journal) __brelse(bh); } - sync_dev(journal->j_dev); + fsync_no_super(journal->j_dev); jbd_debug(1, "JBD: journal cleared.\n"); /* OK, fill in the initial static fields in the new superblock */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/

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