[XFS] There are a few problems with the new

xfs_bmap_search_multi_extents() wrapper function that I introduced in mod
xfs-linux:xfs-kern:207393a. The function was added as a wrapper around
xfs_bmap_do_search_extents() to avoid breaking the top-of-tree CXFS
interface.  The idea of the function was basically to extract the target
extent buffer (if muli- level extent allocation mode), then call
xfs_bmap_do_search_extents() with either a pointer to the first extent in
the target buffer or a pointer to the first extent in the file, depending
on which extent mode was being used.  However, in addition to locating the
target extent record for block bno, xfs_bmap_do_search_extents() also sets
four parameters needed by the caller: *lastx, *eofp, *gotp, *prevp. 
Passing only the target extent buffer to xfs_bmap_do_search_extents()
causes *eofp to be set incorrectly if the extent is at the end of the
target list but there are actually more extents in the next er_extbuf.
Likewise, if the extent is the first one in the buffer but NOT the first
in the file, *prevp is incorrectly set to NULL.  Adding the needed
functionality to xfs_bmap_search_multi_extents() to re-set any incorrectly
set fields is redundant and makes the call to xfs_bmap_do_search_extents()
not make much sense when multi-level extent allocation mode is being used.
 This mod basically extracts the two functional components from
xfs_bmap_do_search_extents(), with the intent of obsoleting/removing
xfs_bmap_do_search_extents() after the CXFS mult-level in-core extent
changes are checked in.  The two components are:  1) The binary search to
locate the target extent record, and 2) Setting the four parameters needed
by the caller (*lastx, *eofp, *gotp, *prevp).  Component 1: I created a
new function in xfs_inode.c called xfs_iext_bno_to_ext(), which executes
the binary search to find the target extent record.
xfs_bmap_search_multi_extents() has been modified to call
xfs_iext_bno_to_ext() rather than xfs_bmap_do_search_extents().  Component
2: The parameter setting functionality has been added to
xfs_bmap_search_multi_extents(), eliminating the need for
xfs_bmap_do_search_extents().  These changes make the removal of
xfs_bmap_do_search_extents() trival once the CXFS changes are in place. 
They also allow us to maintain the current XFS interface, using the new
search function introduced in mod xfs-linux:xfs-kern:207393a.

SGI-PV: 928864
SGI-Modid: xfs-linux-melb:xfs-kern:207866a

Signed-off-by: Mandy Kirkconnell <alkirkco@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>

1 files changed, 71 insertions, 2 deletions

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 580fa0758039..a16df2d435fe 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -4266,11 +4266,80 @@ xfs_iext_destroy(
 }
 
 /*
+ * Return a pointer to the extent record for file system block bno.
+ */
+xfs_bmbt_rec_t *                        /* pointer to found extent record */
+xfs_iext_bno_to_ext(
+        xfs_ifork_t     *ifp,           /* inode fork pointer */
+        xfs_fileoff_t   bno,            /* block number to search for */
+        xfs_extnum_t    *idxp)          /* index of target extent */
+{
+        xfs_bmbt_rec_t  *base;          /* pointer to first extent */
+        xfs_filblks_t   blockcount = 0; /* number of blocks in extent */
+        xfs_bmbt_rec_t  *ep = NULL;     /* pointer to target extent */
+        xfs_ext_irec_t  *erp = NULL;    /* indirection array pointer */
+        int             high;           /* upper boundry in search */
+        xfs_extnum_t    idx = 0;        /* index of target extent */
+        int             low;            /* lower boundry in search */
+        xfs_extnum_t    nextents;       /* number of file extents */
+        xfs_fileoff_t   startoff = 0;   /* start offset of extent */
+
+        nextents = ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t);
+        if (nextents == 0) {
+                *idxp = 0;
+                return NULL;
+        }
+        low = 0;
+        if (ifp->if_flags & XFS_IFEXTIREC) {
+                /* Find target extent list */
+                int     erp_idx = 0;
+                erp = xfs_iext_bno_to_irec(ifp, bno, &erp_idx);
+                base = erp->er_extbuf;
+                high = erp->er_extcount - 1;
+        } else {
+                base = ifp->if_u1.if_extents;
+                high = nextents - 1;
+        }
+        /* Binary search extent records */
+        while (low <= high) {
+                idx = (low + high) >> 1;
+                ep = base + idx;
+                startoff = xfs_bmbt_get_startoff(ep);
+                blockcount = xfs_bmbt_get_blockcount(ep);
+                if (bno < startoff) {
+                        high = idx - 1;
+                } else if (bno >= startoff + blockcount) {
+                        low = idx + 1;
+                } else {
+                        /* Convert back to file-based extent index */
+                        if (ifp->if_flags & XFS_IFEXTIREC) {
+                                idx += erp->er_extoff;
+                        }
+                        *idxp = idx;
+                        return ep;
+                }
+        }
+        /* Convert back to file-based extent index */
+        if (ifp->if_flags & XFS_IFEXTIREC) {
+                idx += erp->er_extoff;
+        }
+        if (bno >= startoff + blockcount) {
+                if (++idx == nextents) {
+                        ep = NULL;
+                } else {
+                        ep = xfs_iext_get_ext(ifp, idx);
+                }
+        }
+        *idxp = idx;
+        return ep;
+}
+
+/*
  * Return a pointer to the indirection array entry containing the
  * extent record for filesystem block bno. Store the index of the
  * target irec in *erp_idxp.
  */
-xfs_ext_irec_t *
+xfs_ext_irec_t *                        /* pointer to found extent record */
 xfs_iext_bno_to_irec(
         xfs_ifork_t     *ifp,           /* inode fork pointer */
         xfs_fileoff_t   bno,            /* block number to search for */
@@ -4278,7 +4347,7 @@ xfs_iext_bno_to_irec(
 {
         xfs_ext_irec_t  *erp = NULL;    /* indirection array pointer */
         xfs_ext_irec_t  *erp_next;      /* next indirection array entry */
-        xfs_extnum_t    erp_idx;        /* indirection array index */
+        int             erp_idx;        /* indirection array index */
         int             nlists;         /* number of extent irec's (lists) */
         int             high;           /* binary search upper limit */
         int             low;            /* binary search lower limit */