On Wed 18-05-11 13:38:47, niraj kulkarni wrote: > Thanks for the reply. That solves most of the problem. > > So now all I need is to gather information of all submitted buffers in > current transactions, and pass it through ioctl to lower layer. > What I am currently doing is adding buffer to a list instead of submitting > them straightaway, and side by side constructing an array holding these > buffer numbers. So i submit this buffer number array through ioctl, and then > actually submit buffer. > > This needs a few kmallocs while I am holding buffer_lock() on few buffers. > So is it potentially deadlocking situation? It shouldn't be if you use proper gfp mask - like GFP_NOFS should be OK. Honza > On Tue, May 17, 2011 at 11:39 PM, Jan Kara <jack@xxxxxxx> wrote: > > > Hello, > > > > On Thu 12-05-11 19:52:21, Niraj Kulkarni wrote: > > > I am trying to implement a concept called Transactional > > > Flash ( > > http://www.usenix.org/event/osdi08/tech/full_papers/prabhakaran/prabhakaran_html/ > > ) > > > > > > in which all writes are flushed to disk (in this case > > > Flash) as a circular linked list of pages. No journaling mechanisms > > > are used. > > > For that I am trying to get list of all buffers to be > > > written (metadata or data) before actually writing them. I thought > > > of 2 approaches : > > > > > > 1. Get conservative list of all buffers before flushing any of them > > > (before commit phase 2) in journal_commit_transaction function. > > > Problem : Metadata writes use temporary buffers which are > > > allocated just before write. > > Well, if I understand the transactional flash concept right, what you > > should do is to replace code committing metadata to the journal by > > something which writes metadata directly to final location. That should be > > relatively easy modification of loops in journal_commit_transaction(). BTW, > > you might want to use ext4/jbd2 instead of ext3/jbd as a base for your > > experiments since ext3 is basically deprecated. > > > > > 2. Instead of submitting buffers straightaway, collect all of them ( > > > data + metadata ) and flush them in end. > > > Problem : i. Possibility of blocking after data buffers are > > > collected but before metadata buffer collection. > > > Since data buffers are locked, this may > > > lead to deadlock. (I am not sure if it is spinlock) > > > > > > ii. Not able to differentiate between > > > metadata buffers and Descriptor buffers. > > > > Honza > > -- > > Jan Kara <jack@xxxxxxx> > > SUSE Labs, CR > > -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
