xfs_repair: set NEEDSREPAIR the first time we write to a filesystem

Add a hook to the buffer cache so that xfs_repair can intercept the
first write to a V5 filesystem to set the NEEDSREPAIR flag.  In the
event that xfs_repair dirties the filesystem and goes down, this ensures
that the sysadmin will have to re-start repair before mounting.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

diff --git a/include/xfs_mount.h b/include/xfs_mount.h
index 75230ca56ab420ca6df17fc2f21f3dc2474bb828..f93a9f11420138ae70fbf05d4180b13b3fdd0588 100644 (file)
--- a/include/xfs_mount.h
+++ b/include/xfs_mount.h
@@ -11,6 +11,8 @@ struct xfs_inode;
 struct xfs_buftarg;
 struct xfs_da_geometry;
 
+typedef void (*buf_writeback_fn)(struct xfs_buf *bp);
+
 /*
  * Define a user-level mount structure with all we need
  * in order to make use of the numerous XFS_* macros.
@@ -95,6 +97,8 @@ typedef struct xfs_mount {
                int     qi_dqperchunk;
        }                       *m_quotainfo;
 
+       buf_writeback_fn        m_buf_writeback_fn;
+
        /*
         * xlog is defined in libxlog and thus is not intialized by libxfs. This
         * allows an application to initialize and store a reference to the log

diff --git a/libxfs/rdwr.c b/libxfs/rdwr.c
index ac783ce3801ec992e5193a74a4f66b701101a8ca..ca272387a76bba9b355eb7351f616fadb41654db 100644 (file)
--- a/libxfs/rdwr.c
+++ b/libxfs/rdwr.c
@@ -812,6 +812,10 @@ libxfs_bwrite(
                return bp->b_error;
        }
 
+       /* Trigger the writeback hook if there is one. */
+       if (bp->b_mount->m_buf_writeback_fn)
+               bp->b_mount->m_buf_writeback_fn(bp);
+
        /*
         * clear any pre-existing error status on the buffer. This can occur if
         * the buffer is corrupt on disk and the repair process doesn't clear

diff --git a/repair/xfs_repair.c b/repair/xfs_repair.c
index e2e99b2166f44f6bc57a60f844b3a55b3cb1cd77..03b7c242d92eba75ffdf357b888e713355679089 100644 (file)
--- a/repair/xfs_repair.c
+++ b/repair/xfs_repair.c
@@ -751,6 +751,104 @@ clear_needsrepair(
                libxfs_buf_relse(bp);
 }
 
+static void
+update_sb_crc_only(
+       struct xfs_buf          *bp)
+{
+       xfs_buf_update_cksum(bp, XFS_SB_CRC_OFF);
+}
+
+/* Forcibly write the primary superblock with the NEEDSREPAIR flag set. */
+static void
+force_needsrepair(
+       struct xfs_mount        *mp)
+{
+       struct xfs_buf_ops      fake_ops;
+       struct xfs_buf          *bp;
+       int                     error;
+
+       if (!xfs_sb_version_hascrc(&mp->m_sb) ||
+           xfs_sb_version_needsrepair(&mp->m_sb))
+               return;
+
+       bp = libxfs_getsb(mp);
+       if (!bp || bp->b_error) {
+               do_log(
+       _("couldn't get superblock to set needsrepair, err=%d\n"),
+                               bp ? bp->b_error : ENOMEM);
+       } else {
+               /*
+                * It's possible that we need to set NEEDSREPAIR before we've
+                * had a chance to fix the summary counters in the primary sb.
+                * With the exception of those counters, phase 1 already
+                * ensured that the geometry makes sense.
+                *
+                * Bad summary counters in the primary super can cause the
+                * write verifier to fail, so substitute a dummy that only sets
+                * the CRC.  In the event of a crash, NEEDSREPAIR will prevent
+                * the kernel from mounting our potentially damaged filesystem
+                * until repair is run again, so it's ok to bypass the usual
+                * verification in this one case.
+                */
+               fake_ops = xfs_sb_buf_ops; /* struct copy */
+               fake_ops.verify_write = update_sb_crc_only;
+
+               mp->m_sb.sb_features_incompat |=
+                               XFS_SB_FEAT_INCOMPAT_NEEDSREPAIR;
+               libxfs_sb_to_disk(bp->b_addr, &mp->m_sb);
+
+               /* Force the primary super to disk immediately. */
+               bp->b_ops = &fake_ops;
+               error = -libxfs_bwrite(bp);
+               bp->b_ops = &xfs_sb_buf_ops;
+               if (error)
+                       do_log(_("couldn't force needsrepair, err=%d\n"), error);
+       }
+       if (bp)
+               libxfs_buf_relse(bp);
+}
+
+/*
+ * Intercept the first non-super write to the filesystem so we can set
+ * NEEDSREPAIR to protect the filesystem from mount in case of a crash.
+ */
+static void
+repair_capture_writeback(
+       struct xfs_buf          *bp)
+{
+       struct xfs_mount        *mp = bp->b_mount;
+       static pthread_mutex_t  wb_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+       /*
+        * This write hook ignores any buffer that looks like a superblock to
+        * avoid hook recursion when setting NEEDSREPAIR.  Higher level code
+        * modifying an sb must control the flag manually.
+        */
+       if (bp->b_ops == &xfs_sb_buf_ops || bp->b_bn == XFS_SB_DADDR)
+               return;
+
+       pthread_mutex_lock(&wb_mutex);
+
+       /*
+        * If someone else already dropped the hook, then needsrepair has
+        * already been set on the filesystem and we can unlock.
+        */
+       if (mp->m_buf_writeback_fn != repair_capture_writeback)
+               goto unlock;
+
+       /*
+        * If we get here, the buffer being written is not a superblock, and
+        * needsrepair needs to be set.  The hook is kept in place to plug all
+        * other writes until the sb write finishes.
+        */
+       force_needsrepair(mp);
+
+       /* We only set needsrepair once, so clear the hook now. */
+       mp->m_buf_writeback_fn = NULL;
+unlock:
+       pthread_mutex_unlock(&wb_mutex);
+}
+
 int
 main(int argc, char **argv)
 {
@@ -847,6 +945,10 @@ main(int argc, char **argv)
        if (verbose > 2)
                mp->m_flags |= LIBXFS_MOUNT_WANT_CORRUPTED;
 
+       /* Capture the first writeback so that we can set needsrepair. */
+       if (xfs_sb_version_hascrc(&mp->m_sb))
+               mp->m_buf_writeback_fn = repair_capture_writeback;
+
        /*
         * set XFS-independent status vars from the mount/sb structure
         */