xfs: streamline the directory iteration code for scrub

Currently, online scrub reuses the xfs_readdir code to walk every entry
in a directory.  This isn't awesome for performance, since we end up
cycling the directory ILOCK needlessly and coding around the particular
quirks of the VFS dir_context interface.

Create a streamlined version of readdir that keeps the ILOCK (since the
walk function isn't going to copy stuff to userspace), skips a whole lot
of directory walk cursor checks (since we start at 0 and walk to the
end) and has a sane way to return error codes.

Note: Porting the dotdot checking code is left for a subsequent patch.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

Author: Darrick J. Wong

fs/xfs/Makefile

@@ -158,6 +158,7 @@ xfs-y				+= $(addprefix scrub/, \
 				   ialloc.o \
 				   inode.o \
 				   parent.o \
+				   readdir.o \
 				   refcount.o \
 				   rmap.o \
 				   scrub.o \

fs/xfs/scrub/dir.c

@@ -18,6 +18,7 @@
 #include "scrub/scrub.h"
 #include "scrub/common.h"
 #include "scrub/dabtree.h"
+#include "scrub/readdir.h"
 
 /* Set us up to scrub directories. */
 int
@@ -31,30 +32,21 @@ xchk_setup_directory(
 
 /* Scrub a directory entry. */
 
-struct xchk_dir_ctx {
-	/* VFS fill-directory iterator */
-	struct dir_context	dir_iter;
-
-	struct xfs_scrub	*sc;
-};
-
-/* Check that an inode's mode matches a given DT_ type. */
+/* Check that an inode's mode matches a given XFS_DIR3_FT_* type. */
 STATIC int
 xchk_dir_check_ftype(
-	struct xchk_dir_ctx	*sdc,
+	struct xfs_scrub	*sc,
 	xfs_fileoff_t		offset,
 	xfs_ino_t		inum,
-	int			dtype)
+	int			ftype)
 {
-	struct xfs_mount	*mp = sdc->sc->mp;
+	struct xfs_mount	*mp = sc->mp;
 	struct xfs_inode	*ip;
-	int			ino_dtype;
 	int			error = 0;
 
 	if (!xfs_has_ftype(mp)) {
-		if (dtype != DT_UNKNOWN && dtype != DT_DIR)
-			xchk_fblock_set_corrupt(sdc->sc, XFS_DATA_FORK,
-					offset);
+		if (ftype != XFS_DIR3_FT_UNKNOWN && ftype != XFS_DIR3_FT_DIR)
+			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
 		goto out;
 	}
 
@@ -71,21 +63,17 @@ xchk_dir_check_ftype(
 	 * -EFSCORRUPTED or -EFSBADCRC then the child is corrupt which is a
 	 *  cross referencing error.  Any other error is an operational error.
 	 */
-	error = xfs_iget(mp, sdc->sc->tp, inum, 0, 0, &ip);
+	error = xfs_iget(mp, sc->tp, inum, 0, 0, &ip);
 	if (error == -EINVAL || error == -ENOENT) {
 		error = -EFSCORRUPTED;
-		xchk_fblock_process_error(sdc->sc, XFS_DATA_FORK, 0, &error);
+		xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, &error);
 		goto out;
 	}
-	if (!xchk_fblock_xref_process_error(sdc->sc, XFS_DATA_FORK, offset,
-			&error))
+	if (!xchk_fblock_xref_process_error(sc, XFS_DATA_FORK, offset, &error))
 		goto out;
 
-	/* Convert mode to the DT_* values that dir_emit uses. */
-	ino_dtype = xfs_dir3_get_dtype(mp,
-			xfs_mode_to_ftype(VFS_I(ip)->i_mode));
-	if (ino_dtype != dtype)
-		xchk_fblock_set_corrupt(sdc->sc, XFS_DATA_FORK, offset);
+	if (xfs_mode_to_ftype(VFS_I(ip)->i_mode) != ftype)
+		xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
 	xfs_irele(ip);
 out:
 	return error;
@@ -94,105 +82,85 @@ xchk_dir_check_ftype(
 /*
  * Scrub a single directory entry.
  *
- * We use the VFS directory iterator (i.e. readdir) to call this
- * function for every directory entry in a directory.  Once we're here,
- * we check the inode number to make sure it's sane, then we check that
- * we can look up this filename.  Finally, we check the ftype.
+ * Check the inode number to make sure it's sane, then we check that we can
+ * look up this filename.  Finally, we check the ftype.
  */
-STATIC bool
+STATIC int
 xchk_dir_actor(
-	struct dir_context	*dir_iter,
-	const char		*name,
-	int			namelen,
-	loff_t			pos,
-	u64			ino,
-	unsigned		type)
+	struct xfs_scrub	*sc,
+	struct xfs_inode	*dp,
+	xfs_dir2_dataptr_t	dapos,
+	const struct xfs_name	*name,
+	xfs_ino_t		ino,
+	void			*priv)
 {
-	struct xfs_mount	*mp;
-	struct xfs_inode	*ip;
-	struct xchk_dir_ctx	*sdc;
-	struct xfs_name		xname;
+	struct xfs_mount	*mp = dp->i_mount;
 	xfs_ino_t		lookup_ino;
 	xfs_dablk_t		offset;
 	bool			checked_ftype = false;
 	int			error = 0;
 
-	sdc = container_of(dir_iter, struct xchk_dir_ctx, dir_iter);
-	ip = sdc->sc->ip;
-	mp = ip->i_mount;
 	offset = xfs_dir2_db_to_da(mp->m_dir_geo,
-			xfs_dir2_dataptr_to_db(mp->m_dir_geo, pos));
+			xfs_dir2_dataptr_to_db(mp->m_dir_geo, dapos));
 
-	if (xchk_should_terminate(sdc->sc, &error))
-		return !error;
+	if (xchk_should_terminate(sc, &error))
+		return error;
 
 	/* Does this inode number make sense? */
 	if (!xfs_verify_dir_ino(mp, ino)) {
-		xchk_fblock_set_corrupt(sdc->sc, XFS_DATA_FORK, offset);
-		goto out;
+		xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
+		return -ECANCELED;
 	}
 
 	/* Does this name make sense? */
-	if (!xfs_dir2_namecheck(name, namelen)) {
-		xchk_fblock_set_corrupt(sdc->sc, XFS_DATA_FORK, offset);
-		goto out;
+	if (!xfs_dir2_namecheck(name->name, name->len)) {
+		xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
+		return -ECANCELED;
 	}
 
-	if (!strncmp(".", name, namelen)) {
+	if (!strncmp(".", name->name, name->len)) {
 		/* If this is "." then check that the inum matches the dir. */
-		if (xfs_has_ftype(mp) && type != DT_DIR)
-			xchk_fblock_set_corrupt(sdc->sc, XFS_DATA_FORK,
-					offset);
+		if (xfs_has_ftype(mp) && name->type != XFS_DIR3_FT_DIR)
+			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
 		checked_ftype = true;
-		if (ino != ip->i_ino)
-			xchk_fblock_set_corrupt(sdc->sc, XFS_DATA_FORK,
-					offset);
-	} else if (!strncmp("..", name, namelen)) {
+		if (ino != dp->i_ino)
+			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
+	} else if (!strncmp("..", name->name, name->len)) {
 		/*
 		 * If this is ".." in the root inode, check that the inum
 		 * matches this dir.
 		 */
-		if (xfs_has_ftype(mp) && type != DT_DIR)
-			xchk_fblock_set_corrupt(sdc->sc, XFS_DATA_FORK,
-					offset);
+		if (xfs_has_ftype(mp) && name->type != XFS_DIR3_FT_DIR)
+			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
 		checked_ftype = true;
-		if (ip->i_ino == mp->m_sb.sb_rootino && ino != ip->i_ino)
-			xchk_fblock_set_corrupt(sdc->sc, XFS_DATA_FORK,
-					offset);
+		if (dp->i_ino == mp->m_sb.sb_rootino && ino != dp->i_ino)
+			xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
 	}
 
 	/* Verify that we can look up this name by hash. */
-	xname.name = name;
-	xname.len = namelen;
-	xname.type = XFS_DIR3_FT_UNKNOWN;
-
-	error = xfs_dir_lookup(sdc->sc->tp, ip, &xname, &lookup_ino, NULL);
+	error = xchk_dir_lookup(sc, dp, name, &lookup_ino);
 	/* ENOENT means the hash lookup failed and the dir is corrupt */
 	if (error == -ENOENT)
 		error = -EFSCORRUPTED;
-	if (!xchk_fblock_process_error(sdc->sc, XFS_DATA_FORK, offset,
-			&error))
+	if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, offset, &error))
 		goto out;
 	if (lookup_ino != ino) {
-		xchk_fblock_set_corrupt(sdc->sc, XFS_DATA_FORK, offset);
-		goto out;
+		xchk_fblock_set_corrupt(sc, XFS_DATA_FORK, offset);
+		return -ECANCELED;
 	}
 
 	/* Verify the file type.  This function absorbs error codes. */
 	if (!checked_ftype) {
-		error = xchk_dir_check_ftype(sdc, offset, lookup_ino, type);
+		error = xchk_dir_check_ftype(sc, offset, lookup_ino,
+				name->type);
 		if (error)
 			goto out;
 	}
+
 out:
-	/*
-	 * A negative error code returned here is supposed to cause the
-	 * dir_emit caller (xfs_readdir) to abort the directory iteration
-	 * and return zero to xchk_directory.
-	 */
-	if (error == 0 && sdc->sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
-		return false;
-	return !error;
+	if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
+		return -ECANCELED;
+	return error;
 }
 
 /* Scrub a directory btree record. */
@@ -808,22 +776,15 @@ int
 xchk_directory(
 	struct xfs_scrub	*sc)
 {
-	struct xchk_dir_ctx	sdc = {
-		.dir_iter.actor = xchk_dir_actor,
-		.dir_iter.pos = 0,
-		.sc = sc,
-	};
-	size_t			bufsize;
-	loff_t			oldpos;
-	int			error = 0;
+	int			error;
 
 	if (!S_ISDIR(VFS_I(sc->ip)->i_mode))
 		return -ENOENT;
 
 	/* Plausible size? */
 	if (sc->ip->i_disk_size < xfs_dir2_sf_hdr_size(0)) {
 		xchk_ino_set_corrupt(sc, sc->ip->i_ino);
-		goto out;
+		return 0;
 	}
 
 	/* Check directory tree structure */
@@ -832,52 +793,19 @@ xchk_directory(
 		return error;
 
 	if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
-		return error;
+		return 0;
 
 	/* Check the freespace. */
 	error = xchk_directory_blocks(sc);
 	if (error)
 		return error;
 
 	if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
-		return error;
-
-	/*
-	 * Check that every dirent we see can also be looked up by hash.
-	 * Userspace usually asks for a 32k buffer, so we will too.
-	 */
-	bufsize = (size_t)min_t(loff_t, XFS_READDIR_BUFSIZE,
-			sc->ip->i_disk_size);
-
-	/*
-	 * Look up every name in this directory by hash.
-	 *
-	 * Use the xfs_readdir function to call xchk_dir_actor on
-	 * every directory entry in this directory.  In _actor, we check
-	 * the name, inode number, and ftype (if applicable) of the
-	 * entry.  xfs_readdir uses the VFS filldir functions to provide
-	 * iteration context.
-	 *
-	 * The VFS grabs a read or write lock via i_rwsem before it reads
-	 * or writes to a directory.  If we've gotten this far we've
-	 * already obtained IOLOCK_EXCL, which (since 4.10) is the same as
-	 * getting a write lock on i_rwsem.  Therefore, it is safe for us
-	 * to drop the ILOCK here in order to reuse the _readdir and
-	 * _dir_lookup routines, which do their own ILOCK locking.
-	 */
-	oldpos = 0;
-	sc->ilock_flags &= ~XFS_ILOCK_EXCL;
-	xfs_iunlock(sc->ip, XFS_ILOCK_EXCL);
-	while (true) {
-		error = xfs_readdir(sc->tp, sc->ip, &sdc.dir_iter, bufsize);
-		if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0,
-				&error))
-			goto out;
-		if (oldpos == sdc.dir_iter.pos)
-			break;
-		oldpos = sdc.dir_iter.pos;
-	}
+		return 0;
 
-out:
+	/* Look up every name in this directory by hash. */
+	error = xchk_dir_walk(sc, sc->ip, xchk_dir_actor, NULL);
+	if (error == -ECANCELED)
+		error = 0;
 	return error;
 }