xfs: fix incorrect remote symlink block count

When CRCs are enabled, the number of blocks needed to hold a remote
symlink on a 1k block size filesystem may be 2 instead of 1. The
transaction reservation for the allocated blocks was not taking this
into account and only allocating one block. Hence when trying to
read or invalidate such symlinks, we are mapping a hole where there
should be a block and things go bad at that point.

Fix the reservation to use the correct block count, clean up the
block count calculation similar to the remote attribute calculation,
and add a debug guard to detect when we don't write the entire
symlink to disk.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
(cherry picked from commit 321a95839e65db3759a07a3655184b0283af90fe)

diff --git a/fs/xfs/xfs_symlink.c b/fs/xfs/xfs_symlink.c
index 5f234389327c806c286c7c1b8a2b0578a4aa8a9f..195a403e1522bbed00cb0f843b1d53c885db0e0d 100644 (file)
--- a/fs/xfs/xfs_symlink.c
+++ b/fs/xfs/xfs_symlink.c
@@ -56,16 +56,9 @@ xfs_symlink_blocks(
        struct xfs_mount *mp,
        int             pathlen)
 {
-       int             fsblocks = 0;
-       int             len = pathlen;
+       int buflen = XFS_SYMLINK_BUF_SPACE(mp, mp->m_sb.sb_blocksize);
 
-       do {
-               fsblocks++;
-               len -= XFS_SYMLINK_BUF_SPACE(mp, mp->m_sb.sb_blocksize);
-       } while (len > 0);
-
-       ASSERT(fsblocks <= XFS_SYMLINK_MAPS);
-       return fsblocks;
+       return (pathlen + buflen - 1) / buflen;
 }
 
 static int
@@ -405,7 +398,7 @@ xfs_symlink(
        if (pathlen <= XFS_LITINO(mp, dp->i_d.di_version))
                fs_blocks = 0;
        else
-               fs_blocks = XFS_B_TO_FSB(mp, pathlen);
+               fs_blocks = xfs_symlink_blocks(mp, pathlen);
        resblks = XFS_SYMLINK_SPACE_RES(mp, link_name->len, fs_blocks);
        error = xfs_trans_reserve(tp, resblks, XFS_SYMLINK_LOG_RES(mp), 0,
                        XFS_TRANS_PERM_LOG_RES, XFS_SYMLINK_LOG_COUNT);
@@ -512,7 +505,7 @@ xfs_symlink(
                cur_chunk = target_path;
                offset = 0;
                for (n = 0; n < nmaps; n++) {
-                       char *buf;
+                       char    *buf;
 
                        d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
                        byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
@@ -525,9 +518,7 @@ xfs_symlink(
                        bp->b_ops = &xfs_symlink_buf_ops;
 
                        byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
-                       if (pathlen < byte_cnt) {
-                               byte_cnt = pathlen;
-                       }
+                       byte_cnt = min(byte_cnt, pathlen);
 
                        buf = bp->b_addr;
                        buf += xfs_symlink_hdr_set(mp, ip->i_ino, offset,
@@ -542,6 +533,7 @@ xfs_symlink(
                        xfs_trans_log_buf(tp, bp, 0, (buf + byte_cnt - 1) -
                                                        (char *)bp->b_addr);
                }
+               ASSERT(pathlen == 0);
        }
 
        /*