xfs: Remove kmem_zone_alloc() usage

Use kmem_cache_alloc() directly.

All kmem_zone_alloc() users pass 0 as flags, which are translated into:
GFP_KERNEL | __GFP_NOWARN, and kmem_zone_alloc() loops forever until the
allocation succeeds.

We can use __GFP_NOFAIL to tell the allocator to loop forever rather
than doing it ourself, and because the allocation will never fail, we do
not need to use __GFP_NOWARN anymore. Hence, all callers can be
converted to use GFP_KERNEL | __GFP_NOFAIL

Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
[darrick: add a comment back in about nofail]
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/libxfs/xfs_alloc.c

@@ -2462,7 +2462,8 @@ xfs_defer_agfl_block(
 	ASSERT(xfs_bmap_free_item_zone != NULL);
 	ASSERT(oinfo != NULL);
 
-	new = kmem_zone_alloc(xfs_bmap_free_item_zone, 0);
+	new = kmem_cache_alloc(xfs_bmap_free_item_zone,
+			       GFP_KERNEL | __GFP_NOFAIL);
 	new->xefi_startblock = XFS_AGB_TO_FSB(mp, agno, agbno);
 	new->xefi_blockcount = 1;
 	new->xefi_oinfo = *oinfo;

fs/xfs/libxfs/xfs_bmap.c

@@ -553,7 +553,8 @@ __xfs_bmap_add_free(
 #endif
 	ASSERT(xfs_bmap_free_item_zone != NULL);
 
-	new = kmem_zone_alloc(xfs_bmap_free_item_zone, 0);
+	new = kmem_cache_alloc(xfs_bmap_free_item_zone,
+			       GFP_KERNEL | __GFP_NOFAIL);
 	new->xefi_startblock = bno;
 	new->xefi_blockcount = (xfs_extlen_t)len;
 	if (oinfo)

fs/xfs/xfs_icache.c

@@ -37,13 +37,11 @@ xfs_inode_alloc(
 	struct xfs_inode	*ip;
 
 	/*
-	 * if this didn't occur in transactions, we could use
-	 * KM_MAYFAIL and return NULL here on ENOMEM. Set the
-	 * code up to do this anyway.
+	 * XXX: If this didn't occur in transactions, we could drop GFP_NOFAIL
+	 * and return NULL here on ENOMEM.
 	 */
-	ip = kmem_zone_alloc(xfs_inode_zone, 0);
-	if (!ip)
-		return NULL;
+	ip = kmem_cache_alloc(xfs_inode_zone, GFP_KERNEL | __GFP_NOFAIL);
+
 	if (inode_init_always(mp->m_super, VFS_I(ip))) {
 		kmem_cache_free(xfs_inode_zone, ip);
 		return NULL;