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[PATCH 5/9] repair: detect CRC errors in AG headers

To: xfs@xxxxxxxxxxx
Subject: [PATCH 5/9] repair: detect CRC errors in AG headers
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 24 Apr 2014 15:01:58 +1000
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1398315722-20870-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1398315722-20870-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

repair doesn't currently detect verifier errors in AG header
blocks - apart from the primary superblock they are not detected.
They are, fortunately, corrected in the important cases (AGF, AGI
and AGFL) because these structures are rebuilt in phase 5, but if
you run xfs_repair in checking mode it won't report them as bad.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 repair/scan.c | 81 ++++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 49 insertions(+), 32 deletions(-)

diff --git a/repair/scan.c b/repair/scan.c
index 1744c32..d022723 100644
--- a/repair/scan.c
+++ b/repair/scan.c
@@ -1207,28 +1207,29 @@ scan_ag(
        void            *arg)
 {
        struct aghdr_cnts *agcnts = arg;
-       xfs_agf_t       *agf;
-       xfs_buf_t       *agfbuf;
+       struct xfs_agf  *agf;
+       struct xfs_buf  *agfbuf = NULL;
        int             agf_dirty = 0;
-       xfs_agi_t       *agi;
-       xfs_buf_t       *agibuf;
+       struct xfs_agi  *agi;
+       struct xfs_buf  *agibuf = NULL;
        int             agi_dirty = 0;
-       xfs_sb_t        *sb;
-       xfs_buf_t       *sbbuf;
+       struct xfs_sb   *sb = NULL;
+       struct xfs_buf  *sbbuf = NULL;
        int             sb_dirty = 0;
        int             status;
+       char            *objname = NULL;
 
        sbbuf = libxfs_readbuf(mp->m_dev, XFS_AG_DADDR(mp, agno, XFS_SB_DADDR),
                                XFS_FSS_TO_BB(mp, 1), 0, &xfs_sb_buf_ops);
        if (!sbbuf)  {
-               do_error(_("can't get root superblock for ag %d\n"), agno);
-               return;
+               objname = _("root superblock");
+               goto out_free;
        }
+
        sb = (xfs_sb_t *)calloc(BBSIZE, 1);
        if (!sb) {
                do_error(_("can't allocate memory for superblock\n"));
-               libxfs_putbuf(sbbuf);
-               return;
+               goto out_free;
        }
        libxfs_sb_from_disk(sb, XFS_BUF_TO_SBP(sbbuf));
 
@@ -1236,10 +1237,8 @@ scan_ag(
                        XFS_AG_DADDR(mp, agno, XFS_AGF_DADDR(mp)),
                        XFS_FSS_TO_BB(mp, 1), 0, &xfs_agf_buf_ops);
        if (!agfbuf)  {
-               do_error(_("can't read agf block for ag %d\n"), agno);
-               libxfs_putbuf(sbbuf);
-               free(sb);
-               return;
+               objname = _("agf block");
+               goto out_free;
        }
        agf = XFS_BUF_TO_AGF(agfbuf);
 
@@ -1247,11 +1246,8 @@ scan_ag(
                        XFS_AG_DADDR(mp, agno, XFS_AGI_DADDR(mp)),
                        XFS_FSS_TO_BB(mp, 1), 0, &xfs_agi_buf_ops);
        if (!agibuf)  {
-               do_error(_("can't read agi block for ag %d\n"), agno);
-               libxfs_putbuf(agfbuf);
-               libxfs_putbuf(sbbuf);
-               free(sb);
-               return;
+               objname = _("agi block");
+               goto out_free;
        }
        agi = XFS_BUF_TO_AGI(agibuf);
 
@@ -1277,7 +1273,7 @@ scan_ag(
                        do_warn(_("would reset bad sb for ag %d\n"), agno);
                }
        }
-       if (status & XR_AG_AGF)  {
+       if (agf_dirty || status & XR_AG_AGF)  {
                if (!no_modify) {
                        do_warn(_("reset bad agf for ag %d\n"), agno);
                        agf_dirty = 1;
@@ -1285,7 +1281,7 @@ scan_ag(
                        do_warn(_("would reset bad agf for ag %d\n"), agno);
                }
        }
-       if (status & XR_AG_AGI)  {
+       if (agi_dirty || status & XR_AG_AGI)  {
                if (!no_modify) {
                        do_warn(_("reset bad agi for ag %d\n"), agno);
                        agi_dirty = 1;
@@ -1295,15 +1291,9 @@ scan_ag(
        }
 
        if (status && no_modify)  {
-               libxfs_putbuf(agibuf);
-               libxfs_putbuf(agfbuf);
-               libxfs_putbuf(sbbuf);
-               free(sb);
-
                do_warn(_("bad uncorrected agheader %d, skipping ag...\n"),
                        agno);
-
-               return;
+               goto out_free;
        }
 
        scan_freelist(agf, agcnts);
@@ -1312,21 +1302,34 @@ scan_ag(
        validate_agi(agi, agno, agcnts);
 
        ASSERT(agi_dirty == 0 || (agi_dirty && !no_modify));
+       ASSERT(agf_dirty == 0 || (agf_dirty && !no_modify));
+       ASSERT(sb_dirty == 0 || (sb_dirty && !no_modify));
+
+       /*
+        * Only pay attention to CRC/verifier errors if we can correct them.
+        * While there, ensure that we corrected a corruption error if the
+        * verifier detected one.
+        */
+       if (!no_modify) {
+               ASSERT(agi_dirty || agibuf->b_error != EFSCORRUPTED);
+               ASSERT(agf_dirty || agfbuf->b_error != EFSCORRUPTED);
+               ASSERT(sb_dirty || sbbuf->b_error != EFSCORRUPTED);
+
+               agi_dirty += (agibuf->b_error == EFSBADCRC);
+               agf_dirty += (agfbuf->b_error == EFSBADCRC);
+               sb_dirty += (sbbuf->b_error == EFSBADCRC);
+       }
 
        if (agi_dirty && !no_modify)
                libxfs_writebuf(agibuf, 0);
        else
                libxfs_putbuf(agibuf);
 
-       ASSERT(agf_dirty == 0 || (agf_dirty && !no_modify));
-
        if (agf_dirty && !no_modify)
                libxfs_writebuf(agfbuf, 0);
        else
                libxfs_putbuf(agfbuf);
 
-       ASSERT(sb_dirty == 0 || (sb_dirty && !no_modify));
-
        if (sb_dirty && !no_modify) {
                if (agno == 0)
                        memcpy(&mp->m_sb, sb, sizeof(xfs_sb_t));
@@ -1341,6 +1344,20 @@ scan_ag(
        print_inode_list(i);
 #endif
        return;
+
+out_free:
+       if (sb)
+               free(sb);
+       if (agibuf)
+               libxfs_putbuf(agibuf);
+       if (agfbuf)
+               libxfs_putbuf(agfbuf);
+       if (sbbuf)
+               libxfs_putbuf(sbbuf);
+       if (objname)
+               do_error(_("can't get %s for ag %d\n"), objname, agno);
+       return;
+
 }
 
 #define SCAN_THREADS 32
-- 
1.9.0

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