[PATCH 16/21] xfs: repair damaged symlinks

["Darrick J. Wong" <darrick.wong@oracle.com>]

From: Darrick J. Wong <darrick.wong@oracle.com>

Repair inconsistent symbolic link data.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/Makefile               |    1 
 fs/xfs/scrub/repair.h         |    2 
 fs/xfs/scrub/scrub.c          |    2 
 fs/xfs/scrub/symlink.c        |    2 
 fs/xfs/scrub/symlink_repair.c |  301 +++++++++++++++++++++++++++++++++++++++++
 5 files changed, 306 insertions(+), 2 deletions(-)
 create mode 100644 fs/xfs/scrub/symlink_repair.c


diff --git a/fs/xfs/Makefile b/fs/xfs/Makefile
index 928c7dd0a28d..36156166fef0 100644
--- a/fs/xfs/Makefile
+++ b/fs/xfs/Makefile
@@ -171,6 +171,7 @@ xfs-y				+= $(addprefix scrub/, \
 				   refcount_repair.o \
 				   repair.o \
 				   rmap_repair.o \
+				   symlink_repair.o \
 				   )
 endif
 endif
diff --git a/fs/xfs/scrub/repair.h b/fs/xfs/scrub/repair.h
index a832ed485e4e..14fa8cf89799 100644
--- a/fs/xfs/scrub/repair.h
+++ b/fs/xfs/scrub/repair.h
@@ -112,6 +112,7 @@ int xfs_repair_refcountbt(struct xfs_scrub_context *sc);
 int xfs_repair_inode(struct xfs_scrub_context *sc);
 int xfs_repair_bmap_data(struct xfs_scrub_context *sc);
 int xfs_repair_bmap_attr(struct xfs_scrub_context *sc);
+int xfs_repair_symlink(struct xfs_scrub_context *sc);
 
 #else
 
@@ -153,6 +154,7 @@ static inline int xfs_repair_rmapbt_setup(
 #define xfs_repair_inode		xfs_repair_notsupported
 #define xfs_repair_bmap_data		xfs_repair_notsupported
 #define xfs_repair_bmap_attr		xfs_repair_notsupported
+#define xfs_repair_symlink		xfs_repair_notsupported
 
 #endif /* CONFIG_XFS_ONLINE_REPAIR */
 
diff --git a/fs/xfs/scrub/scrub.c b/fs/xfs/scrub/scrub.c
index eecb96fe2feb..6d7ae6e0e165 100644
--- a/fs/xfs/scrub/scrub.c
+++ b/fs/xfs/scrub/scrub.c
@@ -329,7 +329,7 @@ static const struct xfs_scrub_meta_ops meta_scrub_ops[] = {
 		.type	= ST_INODE,
 		.setup	= xfs_scrub_setup_symlink,
 		.scrub	= xfs_scrub_symlink,
-		.repair	= xfs_repair_notsupported,
+		.repair	= xfs_repair_symlink,
 	},
 	[XFS_SCRUB_TYPE_PARENT] = {	/* parent pointers */
 		.type	= ST_INODE,
diff --git a/fs/xfs/scrub/symlink.c b/fs/xfs/scrub/symlink.c
index 570a89812116..7f2ba4082705 100644
--- a/fs/xfs/scrub/symlink.c
+++ b/fs/xfs/scrub/symlink.c
@@ -34,7 +34,7 @@ xfs_scrub_setup_symlink(
 	if (!sc->buf)
 		return -ENOMEM;
 
-	return xfs_scrub_setup_inode_contents(sc, ip, 0);
+	return xfs_scrub_setup_inode_contents(sc, ip, XFS_SYMLINK_MAPS);
 }
 
 /* Symbolic links. */
diff --git a/fs/xfs/scrub/symlink_repair.c b/fs/xfs/scrub/symlink_repair.c
new file mode 100644
index 000000000000..acc51eb3a879
--- /dev/null
+++ b/fs/xfs/scrub/symlink_repair.c
@@ -0,0 +1,301 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "xfs_defer.h"
+#include "xfs_btree.h"
+#include "xfs_bit.h"
+#include "xfs_log_format.h"
+#include "xfs_trans.h"
+#include "xfs_sb.h"
+#include "xfs_inode.h"
+#include "xfs_inode_fork.h"
+#include "xfs_symlink.h"
+#include "xfs_bmap.h"
+#include "xfs_quota.h"
+#include "scrub/xfs_scrub.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/trace.h"
+#include "scrub/repair.h"
+
+/*
+ * Symbolic Link Repair
+ * ====================
+ *
+ * There's not much we can do to repair symbolic links -- we truncate them to
+ * the first NULL byte and fix up the remote target block headers if they're
+ * incorrect.  Zero-length symlinks are turned into links to /.
+ */
+
+/* Blow out the whole symlink; replace contents. */
+STATIC int
+xfs_repair_symlink_rewrite(
+	struct xfs_trans	**tpp,
+	struct xfs_inode	*ip,
+	const char		*target_path,
+	int			pathlen)
+{
+	struct xfs_defer_ops	dfops;
+	struct xfs_bmbt_irec	mval[XFS_SYMLINK_MAPS];
+	struct xfs_ifork	*ifp;
+	const char		*cur_chunk;
+	struct xfs_mount	*mp = (*tpp)->t_mountp;
+	struct xfs_buf		*bp;
+	xfs_fsblock_t		first_block;
+	xfs_fileoff_t		first_fsb;
+	xfs_filblks_t		fs_blocks;
+	xfs_daddr_t		d;
+	int			byte_cnt;
+	int			n;
+	int			nmaps;
+	int			offset;
+	int			error = 0;
+
+	ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
+
+	/* Truncate the whole data fork if it wasn't inline. */
+	if (!(ifp->if_flags & XFS_IFINLINE)) {
+		error = xfs_itruncate_extents(tpp, ip, XFS_DATA_FORK, 0);
+		if (error)
+			goto out;
+	}
+
+	/* Blow out the in-core fork and zero the on-disk fork. */
+	xfs_idestroy_fork(ip, XFS_DATA_FORK);
+	ip->i_d.di_format = XFS_DINODE_FMT_EXTENTS;
+	ip->i_d.di_nextents = 0;
+	memset(&ip->i_df, 0, sizeof(struct xfs_ifork));
+	ip->i_df.if_flags |= XFS_IFEXTENTS;
+
+	/* Rewrite an inline symlink. */
+	if (pathlen <= XFS_IFORK_DSIZE(ip)) {
+		xfs_init_local_fork(ip, XFS_DATA_FORK, target_path, pathlen);
+
+		i_size_write(VFS_I(ip), pathlen);
+		ip->i_d.di_size = pathlen;
+		ip->i_d.di_format = XFS_DINODE_FMT_LOCAL;
+		xfs_trans_log_inode(*tpp, ip, XFS_ILOG_DDATA | XFS_ILOG_CORE);
+		goto out;
+
+	}
+
+	/* Rewrite a remote symlink. */
+	fs_blocks = xfs_symlink_blocks(mp, pathlen);
+	first_fsb = 0;
+	nmaps = XFS_SYMLINK_MAPS;
+
+	/* Reserve quota for new blocks. */
+	error = xfs_trans_reserve_quota_nblks(*tpp, ip, fs_blocks, 0,
+			XFS_QMOPT_RES_REGBLKS);
+	if (error)
+		goto out;
+
+	/* Map blocks, write symlink target. */
+	xfs_defer_init(&dfops, &first_block);
+
+	error = xfs_bmapi_write(*tpp, ip, first_fsb, fs_blocks,
+			  XFS_BMAPI_METADATA, &first_block, fs_blocks,
+			  mval, &nmaps, &dfops);
+	if (error)
+		goto out_bmap_cancel;
+
+	ip->i_d.di_size = pathlen;
+	i_size_write(VFS_I(ip), pathlen);
+	xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
+
+	cur_chunk = target_path;
+	offset = 0;
+	for (n = 0; n < nmaps; n++) {
+		char	*buf;
+
+		d = XFS_FSB_TO_DADDR(mp, mval[n].br_startblock);
+		byte_cnt = XFS_FSB_TO_B(mp, mval[n].br_blockcount);
+		bp = xfs_trans_get_buf(*tpp, mp->m_ddev_targp, d,
+				       BTOBB(byte_cnt), 0);
+		if (!bp) {
+			error = -ENOMEM;
+			goto out_bmap_cancel;
+		}
+		bp->b_ops = &xfs_symlink_buf_ops;
+
+		byte_cnt = XFS_SYMLINK_BUF_SPACE(mp, byte_cnt);
+		byte_cnt = min(byte_cnt, pathlen);
+
+		buf = bp->b_addr;
+		buf += xfs_symlink_hdr_set(mp, ip->i_ino, offset,
+					   byte_cnt, bp);
+
+		memcpy(buf, cur_chunk, byte_cnt);
+
+		cur_chunk += byte_cnt;
+		pathlen -= byte_cnt;
+		offset += byte_cnt;
+
+		xfs_trans_buf_set_type(*tpp, bp, XFS_BLFT_SYMLINK_BUF);
+		xfs_trans_log_buf(*tpp, bp, 0, (buf + byte_cnt - 1) -
+						(char *)bp->b_addr);
+	}
+	ASSERT(pathlen == 0);
+
+	error = xfs_defer_finish(tpp, &dfops);
+	if (error)
+		goto out_bmap_cancel;
+
+	return 0;
+
+out_bmap_cancel:
+	xfs_defer_cancel(&dfops);
+out:
+	return error;
+}
+
+/* Fix everything that fails the verifiers in the remote blocks. */
+STATIC int
+xfs_repair_symlink_fix_remotes(
+	struct xfs_scrub_context	*sc,
+	loff_t				len)
+{
+	struct xfs_bmbt_irec		mval[XFS_SYMLINK_MAPS];
+	struct xfs_buf			*bp;
+	xfs_filblks_t			fsblocks;
+	xfs_daddr_t			d;
+	loff_t				offset;
+	unsigned int			byte_cnt;
+	int				n;
+	int				nmaps = XFS_SYMLINK_MAPS;
+	int				nr;
+	int				error;
+
+	fsblocks = xfs_symlink_blocks(sc->mp, len);
+	error = xfs_bmapi_read(sc->ip, 0, fsblocks, mval, &nmaps, 0);
+	if (error)
+		return error;
+
+	offset = 0;
+	for (n = 0; n < nmaps; n++) {
+		d = XFS_FSB_TO_DADDR(sc->mp, mval[n].br_startblock);
+		byte_cnt = XFS_FSB_TO_B(sc->mp, mval[n].br_blockcount);
+
+		error = xfs_trans_read_buf(sc->mp, sc->tp, sc->mp->m_ddev_targp,
+				d, BTOBB(byte_cnt), 0, &bp, NULL);
+		if (error)
+			return error;
+		bp->b_ops = &xfs_symlink_buf_ops;
+
+		byte_cnt = XFS_SYMLINK_BUF_SPACE(sc->mp, byte_cnt);
+		if (len < byte_cnt)
+			byte_cnt = len;
+
+		nr = xfs_symlink_hdr_set(sc->mp, sc->ip->i_ino, offset,
+				byte_cnt, bp);
+
+		len -= byte_cnt;
+		offset += byte_cnt;
+
+		xfs_trans_buf_set_type(sc->tp, bp, XFS_BLFT_SYMLINK_BUF);
+		xfs_trans_log_buf(sc->tp, bp, 0, nr - 1);
+		xfs_trans_brelse(sc->tp, bp);
+	}
+	if (len != 0)
+		return -EFSCORRUPTED;
+
+	return 0;
+}
+
+/* Fix this inline symlink. */
+STATIC int
+xfs_repair_symlink_inline(
+	struct xfs_scrub_context	*sc)
+{
+	struct xfs_inode		*ip = sc->ip;
+	struct xfs_ifork		*ifp;
+	loff_t				len;
+	size_t				newlen;
+
+	ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
+	len = i_size_read(VFS_I(ip));
+	xfs_trans_ijoin(sc->tp, ip, 0);
+
+	if (ifp->if_u1.if_data) {
+		newlen = strnlen(ifp->if_u1.if_data, XFS_IFORK_DSIZE(ip));
+	} else {
+		/* Zero length symlink becomes a root symlink. */
+		ifp->if_u1.if_data = kmem_alloc(4, KM_SLEEP);
+		snprintf(ifp->if_u1.if_data, 4, "/");
+		newlen = 1;
+	}
+
+	if (len > newlen) {
+		i_size_write(VFS_I(ip), newlen);
+		ip->i_d.di_size = newlen;
+		xfs_trans_log_inode(sc->tp, ip, XFS_ILOG_DDATA | XFS_ILOG_CORE);
+	}
+
+	return 0;
+}
+
+/* Repair a remote symlink. */
+STATIC int
+xfs_repair_symlink_remote(
+	struct xfs_scrub_context	*sc)
+{
+	struct xfs_inode		*ip = sc->ip;
+	loff_t				len;
+	size_t				newlen;
+	int				error = 0;
+
+	len = i_size_read(VFS_I(ip));
+	xfs_trans_ijoin(sc->tp, ip, 0);
+
+	error = xfs_repair_symlink_fix_remotes(sc, len);
+	if (error)
+		return error;
+
+	/* Roll transaction, release buffers. */
+	error = xfs_trans_roll_inode(&sc->tp, ip);
+	if (error)
+		return error;
+
+	/* Size set correctly? */
+	len = i_size_read(VFS_I(ip));
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	error = xfs_readlink(ip, sc->buf);
+	xfs_ilock(ip, XFS_ILOCK_EXCL);
+	if (error)
+		return error;
+
+	/*
+	 * Figure out the new target length.  We can't handle zero-length
+	 * symlinks, so make sure that we don't write that out.
+	 */
+	newlen = strnlen(sc->buf, XFS_SYMLINK_MAXLEN);
+	if (newlen == 0) {
+		*((char *)sc->buf) = '/';
+		newlen = 1;
+	}
+
+	if (len > newlen)
+		return xfs_repair_symlink_rewrite(&sc->tp, ip, sc->buf, newlen);
+	return 0;
+}
+
+/* Repair a symbolic link. */
+int
+xfs_repair_symlink(
+	struct xfs_scrub_context	*sc)
+{
+	struct xfs_ifork		*ifp;
+
+	ifp = XFS_IFORK_PTR(sc->ip, XFS_DATA_FORK);
+	if (ifp->if_flags & XFS_IFINLINE)
+		return xfs_repair_symlink_inline(sc);
+	return xfs_repair_symlink_remote(sc);
+}