[PATCH 21/51] e2fsck: Verify extent tree blocks and clear the bad ones

["Darrick J. Wong" <djwong@us.ibm.com>]

When we encounter an extent tree block that passes the header check but fails
the checksum, offer to clear just that extent block instead of failing the
whole tree, which results in the entire inode being wiped out.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
---
 e2fsck/pass1.c   |   34 ++++++++++++++++++++++++++++++++--
 e2fsck/problem.c |   15 +++++++++++++++
 e2fsck/problem.h |    6 ++++++
 3 files changed, 53 insertions(+), 2 deletions(-)


diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
index c382a7b..1ae117d 100644
--- a/e2fsck/pass1.c
+++ b/e2fsck/pass1.c
@@ -1805,6 +1805,7 @@ static void scan_extent_node(e2fsck_t ctx, struct problem_context *pctx,
 	int			is_dir, is_leaf;
 	errcode_t		problem;
 	struct ext2_extent_info	info;
+	int			failed_csum;
 
 	pctx->errcode = ext2fs_extent_get_info(ehandle, &info);
 	if (pctx->errcode)
@@ -1812,11 +1813,25 @@ static void scan_extent_node(e2fsck_t ctx, struct problem_context *pctx,
 
 	pctx->errcode = ext2fs_extent_get(ehandle, EXT2_EXTENT_FIRST_SIB,
 					  &extent);
-	while (!pctx->errcode && info.num_entries-- > 0) {
+	while ((pctx->errcode == 0 ||
+		pctx->errcode == EXT2_ET_EXTENT_CSUM_INVALID) &&
+	       info.num_entries-- > 0) {
+		failed_csum = 0;
 		is_leaf = extent.e_flags & EXT2_EXTENT_FLAGS_LEAF;
 		is_dir = LINUX_S_ISDIR(pctx->inode->i_mode);
 
 		problem = 0;
+		/* Ask to clear a corrupt extent block */
+		if (pctx->errcode == EXT2_ET_EXTENT_CSUM_INVALID) {
+			pctx->blk = extent.e_pblk;
+			pctx->blk2 = extent.e_lblk;
+			pctx->num = extent.e_len;
+			problem = PR_1_EXTENT_CSUM_INVALID;
+			if (fix_problem(ctx, problem, pctx))
+				goto fix_problem_now;
+			failed_csum = 1;
+		}
+
 		if (extent.e_pblk == 0 ||
 		    extent.e_pblk < ctx->fs->super->s_first_data_block ||
 		    extent.e_pblk >= ext2fs_blocks_count(ctx->fs->super))
@@ -1828,12 +1843,24 @@ static void scan_extent_node(e2fsck_t ctx, struct problem_context *pctx,
 			 ext2fs_blocks_count(ctx->fs->super))
 			problem = PR_1_EXTENT_ENDS_BEYOND;
 
+		/* Corrupt but passes checks?  Ask to fix checksum. */
+		if (failed_csum) {
+			pctx->blk = extent.e_pblk;
+			pctx->blk2 = extent.e_lblk;
+			pctx->num = extent.e_len;
+			problem = 0;
+			if (fix_problem(ctx, PR_1_EXTENT_ONLY_CSUM_INVALID,
+					pctx))
+				ext2fs_extent_replace(ehandle, 0, &extent);
+		}
+
 		if (problem) {
 		report_problem:
 			pctx->blk = extent.e_pblk;
 			pctx->blk2 = extent.e_lblk;
 			pctx->num = extent.e_len;
 			if (fix_problem(ctx, problem, pctx)) {
+fix_problem_now:
 				e2fsck_read_bitmaps(ctx);
 				pctx->errcode =
 					ext2fs_extent_delete(ehandle, 0);
@@ -1860,7 +1887,10 @@ static void scan_extent_node(e2fsck_t ctx, struct problem_context *pctx,
 			if (pctx->errcode) {
 				pctx->str = "EXT2_EXTENT_DOWN";
 				problem = PR_1_EXTENT_HEADER_INVALID;
-				if (pctx->errcode == EXT2_ET_EXTENT_HEADER_BAD)
+				if (pctx->errcode ==
+					EXT2_ET_EXTENT_HEADER_BAD ||
+				    pctx->errcode ==
+					EXT2_ET_EXTENT_CSUM_INVALID)
 					goto report_problem;
 				return;
 			}
diff --git a/e2fsck/problem.c b/e2fsck/problem.c
index 95813ce..cd404f8 100644
--- a/e2fsck/problem.c
+++ b/e2fsck/problem.c
@@ -951,6 +951,21 @@ static struct e2fsck_problem problem_table[] = {
 	  N_("The bad @b @i looks @n.  "),
 	  PROMPT_CLEAR, 0 },
 
+	/* Inode extent block checksum does not match extent */
+	{ PR_1_EXTENT_CSUM_INVALID,
+	  N_("@i %i extent block checksum does not match extent\n\t(logical @b "
+	     "%c, @n physical @b %b, len %N)\n"),
+	  PROMPT_CLEAR, 0 },
+
+	/*
+	 * Inode extent block passes checks, but checksum does not match
+	 * extent
+	 */
+	{ PR_1_EXTENT_ONLY_CSUM_INVALID,
+	  N_("@i %i extent block passes checks, but checksum does not match "
+	     "extent\n\t(logical @b %c, @n physical @b %b, len %N)\n"),
+	  PROMPT_FIX, 0 },
+
 	/* Pass 1b errors */
 
 	/* Pass 1B: Rescan for duplicate/bad blocks */
diff --git a/e2fsck/problem.h b/e2fsck/problem.h
index 51a911b..cd9e4ed 100644
--- a/e2fsck/problem.h
+++ b/e2fsck/problem.h
@@ -556,6 +556,12 @@ struct problem_context {
 /* inode passes checks, but checksum does not match inode */
 #define PR_1_INODE_ONLY_CSUM_INVALID	0x010067
 
+/* extent block checksum does not match extent block */
+#define PR_1_EXTENT_CSUM_INVALID	0x010068
+
+/* extent block passes checks, but checksum does not match extent block */
+#define PR_1_EXTENT_ONLY_CSUM_INVALID	0x010069
+
 /*
  * Pass 1b errors
  */