journal_forget(9) [centos man page]

JOURNAL_FORGET(9)					     The Linux Journalling API						 JOURNAL_FORGET(9)

NAME

       journal_forget - bforget for potentially-journaled buffers.

SYNOPSIS

       int journal_forget(handle_t * handle, struct buffer_head * bh);

ARGUMENTS

       handle
	   transaction handle

       bh
	   bh to 'forget'

DESCRIPTION

       We can only do the bforget if there are no commits pending against the buffer. If the buffer is dirty in the current running transaction we
       can safely unlink it.

       bh may not be a journalled buffer at all - it may be a non-JBD buffer which came off the hashtable. Check for this.

       Decrements bh->b_count by one.

       Allow this call even if the handle has aborted --- it may be part of the caller's cleanup after an abort.

AUTHORS

       Roger Gammans <rgammans@computer-surgery.co.uk>
	   Author.

       Stephen Tweedie <sct@redhat.com>
	   Author.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014							 JOURNAL_FORGET(9)

JOURNAL_TRY_TO_FREE_(9) 				     The Linux Journalling API					   JOURNAL_TRY_TO_FREE_(9)

NAME

       journal_try_to_free_buffers - try to free page buffers.

SYNOPSIS

       int journal_try_to_free_buffers(journal_t * journal, struct page * page, gfp_t gfp_mask);

ARGUMENTS

       journal
	   journal for operation

       page
	   to try and free

       gfp_mask
	   we use the mask to detect how hard should we try to release buffers. If __GFP_WAIT and __GFP_FS is set, we wait for commit code to
	   release the buffers.

DESCRIPTION

       For all the buffers on this page, if they are fully written out ordered data, move them onto BUF_CLEAN so try_to_free_buffers can reap
       them.

       This function returns non-zero if we wish try_to_free_buffers to be called. We do this if the page is releasable by try_to_free_buffers. We
       also do it if the page has locked or dirty buffers and the caller wants us to perform sync or async writeout.

       This complicates JBD locking somewhat. We aren't protected by the BKL here. We wish to remove the buffer from its committing or running
       transaction's ->t_datalist via __journal_unfile_buffer.

       This may *change* the value of transaction_t->t_datalist, so anyone who looks at t_datalist needs to lock against this function.

       Even worse, someone may be doing a journal_dirty_data on this buffer. So we need to lock against that.  journal_dirty_data will come out of
       the lock with the buffer dirty, which makes it ineligible for release here.

       Who else is affected by this? hmm... Really the only contender is do_get_write_access - it could be looking at the buffer while
       journal_try_to_free_buffer is changing its state. But that cannot happen because we never reallocate freed data as metadata while the data
       is part of a transaction. Yes?

       Return 0 on failure, 1 on success

AUTHORS

       Roger Gammans <rgammans@computer-surgery.co.uk>
	   Author.

       Stephen Tweedie <sct@redhat.com>
	   Author.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014						   JOURNAL_TRY_TO_FREE_(9)