xfs: xfs_iflush() is no longer necessary

Now we have a cached buffer on inode log items, we don't need
to do buffer lookups when flushing inodes anymore - all we need
to do is lock the buffer and we are ready to go.

This largely gets rid of the need for xfs_iflush(), which is
essentially just a mechanism to look up the buffer and flush the
inode to it. Instead, we can just call xfs_iflush_cluster() with a
few modifications to ensure it also flushes the inode we already
hold locked.

This allows the AIL inode item pushing to be almost entirely
non-blocking in XFS - we won't block unless memory allocation
for the cluster inode lookup blocks or the block device queues are
full.

Writeback during inode reclaim becomes a little more complex because
we now have to lock the buffer ourselves, but otherwise this change
is largely a functional no-op that removes a whole lot of code.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index c4586ac3656af7fd8c2b6f3c2f71858a46d55aeb..4a953904863968dda9f97eec8c5adc92a1152c1c 100644 (file)
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -3450,7 +3450,18 @@ out_release_wip:
        return error;
 }
 
-STATIC int
+/*
+ * Non-blocking flush of dirty inode metadata into the backing buffer.
+ *
+ * The caller must have a reference to the inode and hold the cluster buffer
+ * locked. The function will walk across all the inodes on the cluster buffer it
+ * can find and lock without blocking, and flush them to the cluster buffer.
+ *
+ * On success, the caller must write out the buffer returned in *bp and
+ * release it. On failure, the filesystem will be shut down, the buffer will
+ * have been unlocked and released, and EFSCORRUPTED will be returned.
+ */
+int
 xfs_iflush_cluster(
        struct xfs_inode        *ip,
        struct xfs_buf          *bp)
@@ -3485,8 +3496,6 @@ xfs_iflush_cluster(
 
        for (i = 0; i < nr_found; i++) {
                cip = cilist[i];
-               if (cip == ip)
-                       continue;
 
                /*
                 * because this is an RCU protected lookup, we could find a
@@ -3577,99 +3586,11 @@ out_free:
        kmem_free(cilist);
 out_put:
        xfs_perag_put(pag);
-       return error;
-}
-
-/*
- * Flush dirty inode metadata into the backing buffer.
- *
- * The caller must have the inode lock and the inode flush lock held.  The
- * inode lock will still be held upon return to the caller, and the inode
- * flush lock will be released after the inode has reached the disk.
- *
- * The caller must write out the buffer returned in *bpp and release it.
- */
-int
-xfs_iflush(
-       struct xfs_inode        *ip,
-       struct xfs_buf          **bpp)
-{
-       struct xfs_mount        *mp = ip->i_mount;
-       struct xfs_buf          *bp = NULL;
-       struct xfs_dinode       *dip;
-       int                     error;
-
-       XFS_STATS_INC(mp, xs_iflush_count);
-
-       ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
-       ASSERT(xfs_isiflocked(ip));
-       ASSERT(ip->i_df.if_format != XFS_DINODE_FMT_BTREE ||
-              ip->i_df.if_nextents > XFS_IFORK_MAXEXT(ip, XFS_DATA_FORK));
-
-       *bpp = NULL;
-
-       xfs_iunpin_wait(ip);
-
-       /*
-        * For stale inodes we cannot rely on the backing buffer remaining
-        * stale in cache for the remaining life of the stale inode and so
-        * xfs_imap_to_bp() below may give us a buffer that no longer contains
-        * inodes below. We have to check this after ensuring the inode is
-        * unpinned so that it is safe to reclaim the stale inode after the
-        * flush call.
-        */
-       if (xfs_iflags_test(ip, XFS_ISTALE)) {
-               xfs_ifunlock(ip);
-               return 0;
-       }
-
-       /*
-        * Get the buffer containing the on-disk inode. We are doing a try-lock
-        * operation here, so we may get an EAGAIN error. In that case, return
-        * leaving the inode dirty.
-        *
-        * If we get any other error, we effectively have a corruption situation
-        * and we cannot flush the inode. Abort the flush and shut down.
-        */
-       error = xfs_imap_to_bp(mp, NULL, &ip->i_imap, &dip, &bp, XBF_TRYLOCK);
-       if (error == -EAGAIN) {
-               xfs_ifunlock(ip);
-               return error;
-       }
-       if (error)
-               goto abort;
-
-       /*
-        * If the buffer is pinned then push on the log now so we won't
-        * get stuck waiting in the write for too long.
-        */
-       if (xfs_buf_ispinned(bp))
-               xfs_log_force(mp, 0);
-
-       /*
-        * Flush the provided inode then attempt to gather others from the
-        * cluster into the write.
-        *
-        * Note: Once we attempt to flush an inode, we must run buffer
-        * completion callbacks on any failure. If this fails, simulate an I/O
-        * failure on the buffer and shut down.
-        */
-       error = xfs_iflush_int(ip, bp);
-       if (!error)
-               error = xfs_iflush_cluster(ip, bp);
        if (error) {
                bp->b_flags |= XBF_ASYNC;
                xfs_buf_ioend_fail(bp);
-               goto shutdown;
+               xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
        }
-
-       *bpp = bp;
-       return 0;
-
-abort:
-       xfs_iflush_abort(ip);
-shutdown:
-       xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
        return error;
 }
 
@@ -3687,7 +3608,7 @@ xfs_iflush_int(
        ASSERT(xfs_isiflocked(ip));
        ASSERT(ip->i_df.if_format != XFS_DINODE_FMT_BTREE ||
               ip->i_df.if_nextents > XFS_IFORK_MAXEXT(ip, XFS_DATA_FORK));
-       ASSERT(iip != NULL && iip->ili_fields != 0);
+       ASSERT(iip->ili_item.li_buf == bp);
 
        dip = xfs_buf_offset(bp, ip->i_imap.im_boffset);
 

diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 1534386b430c611c476c345e603a893b04074162..c482e7306fe00cf0e139b944eb813663b25b6f13 100644 (file)
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -426,7 +426,7 @@ int         xfs_log_force_inode(struct xfs_inode *ip);
 void           xfs_iunpin_wait(xfs_inode_t *);
 #define xfs_ipincount(ip)      ((unsigned int) atomic_read(&ip->i_pincount))
 
-int            xfs_iflush(struct xfs_inode *, struct xfs_buf **);
+int            xfs_iflush_cluster(struct xfs_inode *, struct xfs_buf *);
 void           xfs_lock_two_inodes(struct xfs_inode *ip0, uint ip0_mode,
                                struct xfs_inode *ip1, uint ip1_mode);
 

diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
index 697248b7eb2be9b4a883437857af0a9cced66c2a..e8eda2ac25fb41831e0ab82243a7b8c829fdf7e4 100644 (file)
--- a/fs/xfs/xfs_inode_item.c
+++ b/fs/xfs/xfs_inode_item.c
@@ -485,53 +485,38 @@ xfs_inode_item_push(
        uint                    rval = XFS_ITEM_SUCCESS;
        int                     error;
 
-       if (xfs_ipincount(ip) > 0)
+       ASSERT(iip->ili_item.li_buf);
+
+       if (xfs_ipincount(ip) > 0 || xfs_buf_ispinned(bp) ||
+           (ip->i_flags & XFS_ISTALE))
                return XFS_ITEM_PINNED;
 
-       if (!xfs_ilock_nowait(ip, XFS_ILOCK_SHARED))
-               return XFS_ITEM_LOCKED;
+       /* If the inode is already flush locked, we're already flushing. */
+       if (xfs_isiflocked(ip))
+               return XFS_ITEM_FLUSHING;
 
-       /*
-        * Re-check the pincount now that we stabilized the value by
-        * taking the ilock.
-        */
-       if (xfs_ipincount(ip) > 0) {
-               rval = XFS_ITEM_PINNED;
-               goto out_unlock;
-       }
+       if (!xfs_buf_trylock(bp))
+               return XFS_ITEM_LOCKED;
 
-       /*
-        * Stale inode items should force out the iclog.
-        */
-       if (ip->i_flags & XFS_ISTALE) {
-               rval = XFS_ITEM_PINNED;
-               goto out_unlock;
-       }
+       spin_unlock(&lip->li_ailp->ail_lock);
 
        /*
-        * Someone else is already flushing the inode.  Nothing we can do
-        * here but wait for the flush to finish and remove the item from
-        * the AIL.
+        * We need to hold a reference for flushing the cluster buffer as it may
+        * fail the buffer without IO submission. In which case, we better get a
+        * reference for that completion because otherwise we don't get a
+        * reference for IO until we queue the buffer for delwri submission.
         */
-       if (!xfs_iflock_nowait(ip)) {
-               rval = XFS_ITEM_FLUSHING;
-               goto out_unlock;
-       }
-
-       ASSERT(iip->ili_fields != 0 || XFS_FORCED_SHUTDOWN(ip->i_mount));
-       spin_unlock(&lip->li_ailp->ail_lock);
-
-       error = xfs_iflush(ip, &bp);
+       xfs_buf_hold(bp);
+       error = xfs_iflush_cluster(ip, bp);
        if (!error) {
                if (!xfs_buf_delwri_queue(bp, buffer_list))
                        rval = XFS_ITEM_FLUSHING;
                xfs_buf_relse(bp);
-       } else if (error == -EAGAIN)
+       } else {
                rval = XFS_ITEM_LOCKED;
+       }
 
        spin_lock(&lip->li_ailp->ail_lock);
-out_unlock:
-       xfs_iunlock(ip, XFS_ILOCK_SHARED);
        return rval;
 }