diff mbox series

[1/4] xfs_repair: set NEEDSREPAIR the first time we write to a filesystem

Message ID 161404926616.425602.16421331298021628773.stgit@magnolia (mailing list archive)
State Accepted
Headers show
Series xfs_repair: set needsrepair when dirtying filesystems | expand

Commit Message

Darrick J. Wong Feb. 23, 2021, 3:01 a.m. UTC
From: Darrick J. Wong <djwong@kernel.org>

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>
---
 include/xfs_mount.h |    4 ++
 libxfs/rdwr.c       |    4 ++
 repair/xfs_repair.c |  102 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 110 insertions(+)

Comments

Allison Henderson Feb. 24, 2021, 5:39 a.m. UTC | #1
On 2/22/21 8:01 PM, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> 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>
Ok, I think it looks good
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>

> ---
>   include/xfs_mount.h |    4 ++
>   libxfs/rdwr.c       |    4 ++
>   repair/xfs_repair.c |  102 +++++++++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 110 insertions(+)
> 
> 
> diff --git a/include/xfs_mount.h b/include/xfs_mount.h
> index 75230ca5..f93a9f11 100644
> --- 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 ac783ce3..ca272387 100644
> --- 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 e2e99b21..03b7c242 100644
> --- 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
>   	 */
>
Christoph Hellwig Feb. 25, 2021, 8:16 a.m. UTC | #2
> diff --git a/include/xfs_mount.h b/include/xfs_mount.h
> index 75230ca5..f93a9f11 100644
> --- 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);

Any point in adding a typedef that is only used once?

> +	if (!bp || bp->b_error) {
> +		do_log(
> +	_("couldn't get superblock to set needsrepair, err=%d\n"),
> +				bp ? bp->b_error : ENOMEM);

Maybe add a goto out_buf_release goto here to avoid the extra level of
indentation for the normal path?

But the code itself looks good, so:

Reviewed-by: Christoph Hellwig <hch@lst.de>
diff mbox series

Patch

diff --git a/include/xfs_mount.h b/include/xfs_mount.h
index 75230ca5..f93a9f11 100644
--- 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 ac783ce3..ca272387 100644
--- 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 e2e99b21..03b7c242 100644
--- 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
 	 */