xfs: introduce fake roots for inode-rooted btrees

Source kernel commit: 349e1c0380dbb7f552e4ea61b479c293eb076b3f

Create an in-core fake root for inode-rooted btree types so that callers
can generate a whole new btree using the upcoming btree bulk load
function without making the new tree accessible from the rest of the
filesystem.  It is up to the individual btree type to provide a function
to create a staged cursor (presumably with the appropriate callouts to
update the fakeroot) and then commit the staged root back into the
filesystem.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

diff --git a/include/xfs_trace.h b/include/xfs_trace.h
index b03b6cc941ac7242a356458f7dd33df1d649a46a..09b98c5b55edb75d6ad4a7e2da2774b7b64ab6e7 100644 (file)
--- a/include/xfs_trace.h
+++ b/include/xfs_trace.h
@@ -47,6 +47,7 @@
 #define trace_xfs_btree_updkeys(a,b,c)         ((void) 0)
 #define trace_xfs_btree_overlapped_query_range(a,b,c)  ((void) 0)
 #define trace_xfs_btree_commit_afakeroot(a)    ((void) 0)
+#define trace_xfs_btree_commit_ifakeroot(a)    ((void) 0)
 
 #define trace_xfs_free_extent(a,b,c,d,e,f,g)   ((void) 0)
 #define trace_xfs_agf(a,b,c,d)                 ((void) 0)

diff --git a/libxfs/xfs_btree.c b/libxfs/xfs_btree.c
index a2ab7cf3d7d552c7c6c739f601ea4744dd9170d2..a376cc9ca661a2cf14d176091d3677e32b80b76d 100644 (file)
--- a/libxfs/xfs_btree.c
+++ b/libxfs/xfs_btree.c
@@ -642,6 +642,17 @@ xfs_btree_ptr_addr(
                ((char *)block + xfs_btree_ptr_offset(cur, n, level));
 }
 
+struct xfs_ifork *
+xfs_btree_ifork_ptr(
+       struct xfs_btree_cur    *cur)
+{
+       ASSERT(cur->bc_flags & XFS_BTREE_ROOT_IN_INODE);
+
+       if (cur->bc_flags & XFS_BTREE_STAGING)
+               return cur->bc_ino.ifake->if_fork;
+       return XFS_IFORK_PTR(cur->bc_ino.ip, cur->bc_ino.whichfork);
+}
+
 /*
  * Get the root block which is stored in the inode.
  *
@@ -652,9 +663,8 @@ STATIC struct xfs_btree_block *
 xfs_btree_get_iroot(
        struct xfs_btree_cur    *cur)
 {
-       struct xfs_ifork        *ifp;
+       struct xfs_ifork        *ifp = xfs_btree_ifork_ptr(cur);
 
-       ifp = XFS_IFORK_PTR(cur->bc_ino.ip, cur->bc_ino.whichfork);
        return (struct xfs_btree_block *)ifp->if_broot;
 }
 

diff --git a/libxfs/xfs_btree.h b/libxfs/xfs_btree.h
index 82b906b55824b123dc2bdc2403ec163db0a46868..07b1d2802bdc8fd7ed46d0e0cf942bd889e805c7 100644 (file)
--- a/libxfs/xfs_btree.h
+++ b/libxfs/xfs_btree.h
@@ -10,6 +10,7 @@ struct xfs_buf;
 struct xfs_inode;
 struct xfs_mount;
 struct xfs_trans;
+struct xfs_ifork;
 
 extern kmem_zone_t     *xfs_btree_cur_zone;
 
@@ -198,6 +199,7 @@ struct xfs_btree_cur_ag {
 /* Btree-in-inode cursor information */
 struct xfs_btree_cur_ino {
        struct xfs_inode                *ip;
+       struct xbtree_ifakeroot         *ifake; /* for staging cursor */
        int                             allocated;
        short                           forksize;
        char                            whichfork;
@@ -509,6 +511,7 @@ union xfs_btree_key *xfs_btree_high_key_from_key(struct xfs_btree_cur *cur,
 int xfs_btree_has_record(struct xfs_btree_cur *cur, union xfs_btree_irec *low,
                union xfs_btree_irec *high, bool *exists);
 bool xfs_btree_has_more_records(struct xfs_btree_cur *cur);
+struct xfs_ifork *xfs_btree_ifork_ptr(struct xfs_btree_cur *cur);
 
 /* Does this cursor point to the last block in the given level? */
 static inline bool

diff --git a/libxfs/xfs_btree_staging.c b/libxfs/xfs_btree_staging.c
index 247683c680456fc77e9e6f6e6fcb913293218939..d4c52d4feb252289e56352b781211f8f4f2e594b 100644 (file)
--- a/libxfs/xfs_btree_staging.c
+++ b/libxfs/xfs_btree_staging.c
@@ -177,3 +177,87 @@ xfs_btree_commit_afakeroot(
        cur->bc_flags &= ~XFS_BTREE_STAGING;
        cur->bc_tp = tp;
 }
+
+/*
+ * Bulk Loading for Inode-Rooted Btrees
+ * ====================================
+ *
+ * For a btree rooted in an inode fork, pass a xbtree_ifakeroot structure to
+ * the staging cursor.  This structure should be initialized as follows:
+ *
+ * - if_fork_size field should be set to the number of bytes available to the
+ *   fork in the inode.
+ *
+ * - if_fork should point to a freshly allocated struct xfs_ifork.
+ *
+ * - if_format should be set to the appropriate fork type (e.g.
+ *   XFS_DINODE_FMT_BTREE).
+ *
+ * All other fields must be zero.
+ *
+ * The _stage_cursor() function for a specific btree type should call
+ * xfs_btree_stage_ifakeroot to set up the in-memory cursor as a staging
+ * cursor.  The corresponding _commit_staged_btree() function should log the
+ * new root and call xfs_btree_commit_ifakeroot() to transform the staging
+ * cursor into a regular btree cursor.
+ */
+
+/*
+ * Initialize an inode-rooted btree cursor with the given inode btree fake
+ * root.  The btree cursor's bc_ops will be overridden as needed to make the
+ * staging functionality work.  If new_ops is not NULL, these new ops will be
+ * passed out to the caller for further overriding.
+ */
+void
+xfs_btree_stage_ifakeroot(
+       struct xfs_btree_cur            *cur,
+       struct xbtree_ifakeroot         *ifake,
+       struct xfs_btree_ops            **new_ops)
+{
+       struct xfs_btree_ops            *nops;
+
+       ASSERT(!(cur->bc_flags & XFS_BTREE_STAGING));
+       ASSERT(cur->bc_flags & XFS_BTREE_ROOT_IN_INODE);
+       ASSERT(cur->bc_tp == NULL);
+
+       nops = kmem_alloc(sizeof(struct xfs_btree_ops), KM_NOFS);
+       memcpy(nops, cur->bc_ops, sizeof(struct xfs_btree_ops));
+       nops->alloc_block = xfs_btree_fakeroot_alloc_block;
+       nops->free_block = xfs_btree_fakeroot_free_block;
+       nops->init_ptr_from_cur = xfs_btree_fakeroot_init_ptr_from_cur;
+       nops->dup_cursor = xfs_btree_fakeroot_dup_cursor;
+
+       cur->bc_ino.ifake = ifake;
+       cur->bc_nlevels = ifake->if_levels;
+       cur->bc_ops = nops;
+       cur->bc_flags |= XFS_BTREE_STAGING;
+
+       if (new_ops)
+               *new_ops = nops;
+}
+
+/*
+ * Transform an inode-rooted staging btree cursor back into a regular cursor by
+ * substituting a real btree root for the fake one and restoring normal btree
+ * cursor ops.  The caller must log the btree root change prior to calling
+ * this.
+ */
+void
+xfs_btree_commit_ifakeroot(
+       struct xfs_btree_cur            *cur,
+       struct xfs_trans                *tp,
+       int                             whichfork,
+       const struct xfs_btree_ops      *ops)
+{
+       ASSERT(cur->bc_flags & XFS_BTREE_STAGING);
+       ASSERT(cur->bc_tp == NULL);
+
+       trace_xfs_btree_commit_ifakeroot(cur);
+
+       kmem_free((void *)cur->bc_ops);
+       cur->bc_ino.ifake = NULL;
+       cur->bc_ino.whichfork = whichfork;
+       cur->bc_ops = ops;
+       cur->bc_flags &= ~XFS_BTREE_STAGING;
+       cur->bc_tp = tp;
+}

diff --git a/libxfs/xfs_btree_staging.h b/libxfs/xfs_btree_staging.h
index 5d78e13d2968c664396856eeeac23078488d46a0..f50dbbb505d12771b581fdfa1583d65b7b65bdf9 100644 (file)
--- a/libxfs/xfs_btree_staging.h
+++ b/libxfs/xfs_btree_staging.h
@@ -24,4 +24,32 @@ void xfs_btree_stage_afakeroot(struct xfs_btree_cur *cur,
 void xfs_btree_commit_afakeroot(struct xfs_btree_cur *cur, struct xfs_trans *tp,
                struct xfs_buf *agbp, const struct xfs_btree_ops *ops);
 
+/* Fake root for an inode-rooted btree. */
+struct xbtree_ifakeroot {
+       /* Fake inode fork. */
+       struct xfs_ifork        *if_fork;
+
+       /* Number of blocks used by the btree. */
+       int64_t                 if_blocks;
+
+       /* Height of the new btree. */
+       unsigned int            if_levels;
+
+       /* Number of bytes available for this fork in the inode. */
+       unsigned int            if_fork_size;
+
+       /* Fork format. */
+       unsigned int            if_format;
+
+       /* Number of records. */
+       unsigned int            if_extents;
+};
+
+/* Cursor interactions with with fake roots for inode-rooted btrees. */
+void xfs_btree_stage_ifakeroot(struct xfs_btree_cur *cur,
+               struct xbtree_ifakeroot *ifake,
+               struct xfs_btree_ops **new_ops);
+void xfs_btree_commit_ifakeroot(struct xfs_btree_cur *cur, struct xfs_trans *tp,
+               int whichfork, const struct xfs_btree_ops *ops);
+
 #endif /* __XFS_BTREE_STAGING_H__ */