xfs: remove unnecessary null pointer checks from _read_agf callers

Drop the null buffer pointer checks in all code that calls
xfs_alloc_read_agf and doesn't pass XFS_ALLOC_FLAG_TRYLOCK because
they're no longer necessary.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/scrub/agheader_repair.c

@@ -659,8 +659,6 @@ xrep_agfl(
 	error = xfs_alloc_read_agf(mp, sc->tp, sc->sa.agno, 0, &agf_bp);
 	if (error)
 		return error;
-	if (!agf_bp)
-		return -ENOMEM;
 
 	/*
 	 * Make sure we have the AGFL buffer, as scrub might have decided it
@@ -735,8 +733,6 @@ xrep_agi_find_btrees(
 	error = xfs_alloc_read_agf(mp, sc->tp, sc->sa.agno, 0, &agf_bp);
 	if (error)
 		return error;
-	if (!agf_bp)
-		return -ENOMEM;
 
 	/* Find the btree roots. */
 	error = xrep_find_ag_btree_roots(sc, agf_bp, fab, NULL);

fs/xfs/scrub/fscounters.c

@@ -83,9 +83,6 @@ xchk_fscount_warmup(
 		error = xfs_alloc_read_agf(mp, sc->tp, agno, 0, &agf_bp);
 		if (error)
 			break;
-		error = -ENOMEM;
-		if (!agf_bp || !agi_bp)
-			break;
 
 		/*
 		 * These are supposed to be initialized by the header read

fs/xfs/scrub/repair.c

@@ -546,8 +546,6 @@ xrep_reap_block(
 		error = xfs_alloc_read_agf(sc->mp, sc->tp, agno, 0, &agf_bp);
 		if (error)
 			return error;
-		if (!agf_bp)
-			return -ENOMEM;
 	} else {
 		agf_bp = sc->sa.agf_bp;
 	}