xfs: introduce xfs_bmapi_read()

xfs_bmapi() currently handles both extent map reading and
allocation. As a result, the code is littered with "if (wr)"
branches to conditionally do allocation operations if required.
This makes the code much harder to follow and causes significant
indent issues with the code.

Given that read mapping is much simpler than allocation, we can
split out read mapping from xfs_bmapi() and reuse the logic that
we have already factored out do do all the hard work of handling the
extent map manipulations. The results in a much simpler function for
the common extent read operations, and will allow the allocation
code to be simplified in another commit.

Once xfs_bmapi_read() is implemented, convert all the callers of
xfs_bmapi() that are only reading extents to use the new function.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 97 insertions, 7 deletions

diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index 59f63949d3bc..fc5acf0b921e 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/fs/xfs/xfs_bmap.c
@@ -4350,6 +4350,98 @@ xfs_bmapi_update_map(
 }
 
 /*
+ * Map file blocks to filesystem blocks without allocation.
+ */
+int
+xfs_bmapi_read(
+        struct xfs_inode        *ip,
+        xfs_fileoff_t           bno,
+        xfs_filblks_t           len,
+        struct xfs_bmbt_irec    *mval,
+        int                     *nmap,
+        int                     flags)
+{
+        struct xfs_mount        *mp = ip->i_mount;
+        struct xfs_ifork        *ifp;
+        struct xfs_bmbt_irec    got;
+        struct xfs_bmbt_irec    prev;
+        xfs_fileoff_t           obno;
+        xfs_fileoff_t           end;
+        xfs_extnum_t            lastx;
+        int                     error;
+        int                     eof;
+        int                     n = 0;
+        int                     whichfork = (flags & XFS_BMAPI_ATTRFORK) ?
+                                                XFS_ATTR_FORK : XFS_DATA_FORK;
+
+        ASSERT(*nmap >= 1);
+        ASSERT(!(flags & ~(XFS_BMAPI_ATTRFORK|XFS_BMAPI_ENTIRE|
+                           XFS_BMAPI_IGSTATE)));
+
+        if (unlikely(XFS_TEST_ERROR(
+            (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
+             XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE),
+             mp, XFS_ERRTAG_BMAPIFORMAT, XFS_RANDOM_BMAPIFORMAT))) {
+                XFS_ERROR_REPORT("xfs_bmapi_read", XFS_ERRLEVEL_LOW, mp);
+                return XFS_ERROR(EFSCORRUPTED);
+        }
+
+        if (XFS_FORCED_SHUTDOWN(mp))
+                return XFS_ERROR(EIO);
+
+        XFS_STATS_INC(xs_blk_mapr);
+
+        ifp = XFS_IFORK_PTR(ip, whichfork);
+        ASSERT(ifp->if_ext_max ==
+               XFS_IFORK_SIZE(ip, whichfork) / (uint)sizeof(xfs_bmbt_rec_t));
+
+        if (!(ifp->if_flags & XFS_IFEXTENTS)) {
+                error = xfs_iread_extents(NULL, ip, whichfork);
+                if (error)
+                        return error;
+        }
+
+        xfs_bmap_search_extents(ip, bno, whichfork, &eof, &lastx, &got, &prev);
+        end = bno + len;
+        obno = bno;
+
+        while (bno < end && n < *nmap) {
+                /* Reading past eof, act as though there's a hole up to end. */
+                if (eof)
+                        got.br_startoff = end;
+                if (got.br_startoff > bno) {
+                        /* Reading in a hole.  */
+                        mval->br_startoff = bno;
+                        mval->br_startblock = HOLESTARTBLOCK;
+                        mval->br_blockcount =
+                                XFS_FILBLKS_MIN(len, got.br_startoff - bno);
+                        mval->br_state = XFS_EXT_NORM;
+                        bno += mval->br_blockcount;
+                        len -= mval->br_blockcount;
+                        mval++;
+                        n++;
+                        continue;
+                }
+
+                /* set up the extent map to return. */
+                xfs_bmapi_trim_map(mval, &got, &bno, len, obno, end, n, flags);
+                xfs_bmapi_update_map(&mval, &bno, &len, obno, end, &n, flags);
+
+                /* If we're done, stop now. */
+                if (bno >= end || n >= *nmap)
+                        break;
+
+                /* Else go on to the next record. */
+                if (++lastx < ifp->if_bytes / sizeof(xfs_bmbt_rec_t))
+                        xfs_bmbt_get_all(xfs_iext_get_ext(ifp, lastx), &got);
+                else
+                        eof = 1;
+        }
+        *nmap = n;
+        return 0;
+}
+
+/*
  * Map file blocks to filesystem blocks.
  * File range is given by the bno/len pair.
  * Adds blocks to file if a write ("flags & XFS_BMAPI_WRITE" set)
@@ -5490,10 +5582,9 @@ xfs_getbmap(
 
         do {
                 nmap = (nexleft > subnex) ? subnex : nexleft;
-                error = xfs_bmapi(NULL, ip, XFS_BB_TO_FSBT(mp, bmv->bmv_offset),
-                                  XFS_BB_TO_FSB(mp, bmv->bmv_length),
-                                  bmapi_flags, NULL, 0, map, &nmap,
-                                  NULL);
+                error = xfs_bmapi_read(ip, XFS_BB_TO_FSBT(mp, bmv->bmv_offset),
+                                       XFS_BB_TO_FSB(mp, bmv->bmv_length),
+                                       map, &nmap, bmapi_flags);
                 if (error)
                         goto out_free_map;
                 ASSERT(nmap <= subnex);
@@ -6084,9 +6175,8 @@ xfs_bmap_punch_delalloc_range(
                  * trying to remove a real extent (which requires a
                  * transaction) or a hole, which is probably a bad idea...
                  */
-                error = xfs_bmapi(NULL, ip, start_fsb, 1,
-                                XFS_BMAPI_ENTIRE,  NULL, 0, &imap,
-                                &nimaps, NULL);
+                error = xfs_bmapi_read(ip, start_fsb, 1, &imap, &nimaps,
+                                       XFS_BMAPI_ENTIRE);
 
                 if (error) {
                         /* something screwed, just bail */