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Date:      Mon, 27 Apr 2020 02:01:48 +0000 (UTC)
From:      Xin LI <delphij@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r360359 - head/sbin/fsck_msdosfs
Message-ID:  <202004270201.03R21mdA058857@repo.freebsd.org>
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Author: delphij
Date: Mon Apr 27 02:01:48 2020
New Revision: 360359
URL: https://svnweb.freebsd.org/changeset/base/360359

Log:
  Fix a bug with dirty file system handling.
  
  r356313 broke handling of dirty file system because we have restricted
  the correction of "odd" byte sequences to checkfat(), and as a result
  the dirty bit is never cleared.  The old fsck_msdosfs code would write
  FAT twice to fix the dirty bit, which is also not ideal.
  
  Fix this by introducing a new rountine, cleardirty() which will perform
  the set of clean bit only, and use it in checkfilesys() if we thought
  the file system was dirty.
  
  Reviewed by:		cem, emaste
  MFC after:		3 day
  Differential Revision:	https://reviews.freebsd.org/D24581

Modified:
  head/sbin/fsck_msdosfs/check.c
  head/sbin/fsck_msdosfs/ext.h
  head/sbin/fsck_msdosfs/fat.c

Modified: head/sbin/fsck_msdosfs/check.c
==============================================================================
--- head/sbin/fsck_msdosfs/check.c	Sun Apr 26 22:08:47 2020	(r360358)
+++ head/sbin/fsck_msdosfs/check.c	Mon Apr 27 02:01:48 2020	(r360359)
@@ -169,7 +169,7 @@ checkfilesys(const char *fname)
 
 			if (mod & FSDIRTY) {
 				pwarn("MARKING FILE SYSTEM CLEAN\n");
-				mod |= writefat(fat);
+				mod |= cleardirty(fat);
 			} else {
 				pwarn("\n***** FILE SYSTEM IS LEFT MARKED AS DIRTY *****\n");
 				mod |= FSERROR; /* file system not clean */

Modified: head/sbin/fsck_msdosfs/ext.h
==============================================================================
--- head/sbin/fsck_msdosfs/ext.h	Sun Apr 26 22:08:47 2020	(r360358)
+++ head/sbin/fsck_msdosfs/ext.h	Mon Apr 27 02:01:48 2020	(r360359)
@@ -90,6 +90,8 @@ int writefsinfo(int, struct bootblock *);
 /* Opaque type */
 struct fat_descriptor;
 
+int cleardirty(struct fat_descriptor *);
+
 void fat_clear_cl_head(struct fat_descriptor *, cl_t);
 bool fat_is_cl_head(struct fat_descriptor *, cl_t);
 

Modified: head/sbin/fsck_msdosfs/fat.c
==============================================================================
--- head/sbin/fsck_msdosfs/fat.c	Sun Apr 26 22:08:47 2020	(r360358)
+++ head/sbin/fsck_msdosfs/fat.c	Mon Apr 27 02:01:48 2020	(r360359)
@@ -578,7 +578,6 @@ valid_cl(struct fat_descriptor *fat, cl_t cl)
  * h = hard error flag (1 = ok; 0 = I/O error)
  * x = any value ok
  */
-
 int
 checkdirty(int fs, struct bootblock *boot)
 {
@@ -636,6 +635,53 @@ checkdirty(int fs, struct bootblock *boot)
 		if ((buffer[7] & 0x0c) == 0x0c)
 			ret = 1;
 	}
+
+err:
+	free(buffer);
+	return ret;
+}
+
+int
+cleardirty(struct fat_descriptor *fat)
+{
+	int fd, ret = FSERROR;
+	struct bootblock *boot;
+	u_char *buffer;
+	size_t len;
+	off_t off;
+
+	boot = boot_of_(fat);
+	fd = fd_of_(fat);
+
+	if (boot->ClustMask != CLUST16_MASK && boot->ClustMask != CLUST32_MASK)
+		return 0;
+
+	off = boot->bpbResSectors;
+	off *= boot->bpbBytesPerSec;
+
+	buffer = malloc(len = boot->bpbBytesPerSec);
+	if (buffer == NULL) {
+		perr("No memory for FAT sectors (%zu)", len);
+		return 1;
+	}
+
+	if ((size_t)pread(fd, buffer, len, off) != len) {
+		perr("Unable to read FAT");
+		goto err;
+	}
+
+	if (boot->ClustMask == CLUST16_MASK) {
+		buffer[3] |= 0x80;
+	} else {
+		buffer[7] |= 0x08;
+	}
+
+	if ((size_t)pwrite(fd, buffer, len, off) != len) {
+		perr("Unable to write FAT");
+		goto err;
+	}
+
+	ret = FSOK;
 
 err:
 	free(buffer);

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