On Fri, Aug 25, 2017 at 11:05:56AM -0400, Brian Foster wrote: > Ordered buffers are used in situations where the buffer is not > physically logged but must pass through the transaction/logging > pipeline for a particular transaction. As a result, ordered buffers > are not unpinned and written back until the transaction commits to > the log. Ordered buffers have a strict requirement that the target > buffer must not be currently dirty and resident in the log pipeline > at the time it is marked ordered. If a dirty+ordered buffer is > committed, the buffer is reinserted to the AIL but not physically > relogged at the LSN of the associated checkpoint. The buffer log > item is assigned the LSN of the latest checkpoint and the AIL > effectively releases the previously logged buffer content from the > active log before the buffer has been written back. If the tail > pushes forward and a filesystem crash occurs while in this state, an > inconsistent filesystem could result. > > It is currently the caller responsibility to ensure an ordered > buffer is not already dirty from a previous modification. This is > unclear and error prone when not used in situations where it is > guaranteed a buffer has not been previously modified (such as new > metadata allocations). > > To facilitate general purpose use of ordered buffers, update > xfs_trans_ordered_buf() to conditionally order the buffer based on > state of the log item and return the status of the result. If the > bli is dirty, do not order the buffer and return false. The caller > must either physically log the buffer (having acquired the > appropriate log reservation) or push it from the AIL to clean it > before it can be marked ordered in the current transaction. > > Note that ordered buffers are currently only used in two situations: > 1.) inode chunk allocation where previously logged buffers are not > possible and 2.) extent swap which will be updated to handle ordered > buffer failures in a separate patch. > > Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx> Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > --- > fs/xfs/xfs_trans.h | 2 +- > fs/xfs/xfs_trans_buf.c | 7 +++++-- > 2 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h > index b3632eb..4709823 100644 > --- a/fs/xfs/xfs_trans.h > +++ b/fs/xfs/xfs_trans.h > @@ -212,7 +212,7 @@ void xfs_trans_bhold_release(xfs_trans_t *, struct xfs_buf *); > void xfs_trans_binval(xfs_trans_t *, struct xfs_buf *); > void xfs_trans_inode_buf(xfs_trans_t *, struct xfs_buf *); > void xfs_trans_stale_inode_buf(xfs_trans_t *, struct xfs_buf *); > -void xfs_trans_ordered_buf(xfs_trans_t *, struct xfs_buf *); > +bool xfs_trans_ordered_buf(xfs_trans_t *, struct xfs_buf *); > void xfs_trans_dquot_buf(xfs_trans_t *, struct xfs_buf *, uint); > void xfs_trans_inode_alloc_buf(xfs_trans_t *, struct xfs_buf *); > void xfs_trans_ichgtime(struct xfs_trans *, struct xfs_inode *, int); > diff --git a/fs/xfs/xfs_trans_buf.c b/fs/xfs/xfs_trans_buf.c > index 3089e80..3ba7a96 100644 > --- a/fs/xfs/xfs_trans_buf.c > +++ b/fs/xfs/xfs_trans_buf.c > @@ -724,7 +724,7 @@ xfs_trans_inode_alloc_buf( > * transactions rather than the physical changes we make to the buffer without > * changing writeback ordering constraints of metadata buffers. > */ > -void > +bool > xfs_trans_ordered_buf( > struct xfs_trans *tp, > struct xfs_buf *bp) > @@ -734,7 +734,9 @@ xfs_trans_ordered_buf( > ASSERT(bp->b_transp == tp); > ASSERT(bip != NULL); > ASSERT(atomic_read(&bip->bli_refcount) > 0); > - ASSERT(!xfs_buf_item_dirty_format(bip)); > + > + if (xfs_buf_item_dirty_format(bip)) > + return false; > > bip->bli_flags |= XFS_BLI_ORDERED; > trace_xfs_buf_item_ordered(bip); > @@ -744,6 +746,7 @@ xfs_trans_ordered_buf( > * to be marked dirty and that it has been logged. > */ > xfs_trans_dirty_buf(tp, bp); > + return true; > } > > /* > -- > 2.9.5 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
