| Message ID | 20170825150557.43010-9-bfoster@redhat.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
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@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> > --- > 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@vger.kernel.org > 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
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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; } /*
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@redhat.com> --- fs/xfs/xfs_trans.h | 2 +- fs/xfs/xfs_trans_buf.c | 7 +++++-- 2 files changed, 6 insertions(+), 3 deletions(-)