Bug 115174 - [patch] growfs(8) needs zero-writing for safe filesystem expansion
Summary: [patch] growfs(8) needs zero-writing for safe filesystem expansion
Status: Closed FIXED
Alias: None
Product: Base System
Classification: Unclassified
Component: bin (show other bugs)
Version: 6.2-RELEASE
Hardware: Any Any
: Normal Affects Only Me
Assignee: Gavin Atkinson
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2007-08-03 17:30 UTC by Veronica
Modified: 2010-03-17 20:40 UTC (History)
0 users

See Also:


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Description Veronica 2007-08-03 17:30:01 UTC
I am writing capacity expansion support for geom_raid5, created by Arne
Woerner. This expansion works great, yet I also need growfs to expand
the filesystem on it afterwards. Through testing Arne and I discovered
a bug or weakness in growfs: it will wrongfully assume the expanded disk
area is full of zero's.

growfs itself does not show any error and seems to work fine. It is the
fsck afterwards that *can* kill a lot of data. It's safe to assume this
is caused by 'stale' data on the expanded disk area, which confuses fsck
because it thinks its part of the filesystem where in fact it is not
'active' filesystem data. In most cases, fsck will report a ton of errors,
clear bogus files and leave you with a healthy filesystem where only your
original files remained.

In some cases, though, I managed to kill off about 40% of my original
files after expanding using growfs. I did a fsck before using growfs to
verify the filesystem was clean, after using growfs I ran fsck again and
it did an 'extra step' (2b I think) to find more DUPs (duplicate inodes
I assume?). After fsck finished, it left me with a crippled filesystem
where lots of files were gone. Also fsck was not able to resolve all
issues, no matter how much I ran fsck there remained some errors. I
suspect this is because the bogus data in the expanded area was part of
a real UFS filesystem in the past, and as such many UFS file structures
remained that would have confused fsck.

This behavior is not acceptable! Simply referring to the "you should
have made a backup" is no excuse for having a flawed growfs. Growfs is
required to make a proper RAID5 expansion possible - a feature that will
be quite hot when geom_raid5 is integrated into FreeBSD source tree.
Please help resolve this issue and pave the way for the "Just Works"
principle that makes software popular and sexy.

Fix: 

The solution is rather simple: growfs should write zeroes to the expanding
area before writing the metadata structures. This will ensure no bogus
filesystem structures exist which may lead to fsck mutilating the
filesystem. Until such feature exists, the manpage should make it very
clear that a zero-write procedure has to be performed manually, using dd.

Workaround:
before using growfs, blank the area using dd:
dd if=/dev/zero of=<disk> bs=512 oseek=<sector starting with expansion>

Contact via email for details. - Veronica
How-To-Repeat: * create a filesystem shorter than the device, using the -s argument and
  populate with data:

newfs -s 30000 /dev/ad4
mount /dev/ad4 /mnt
(copy data onto /mnt until its full)
umount /dev/ad4

* now write random data to the area which will be expanded
dd if=/dev/urandom of=/dev/ad4 oseek=30000 bs=512

* check filesystem for errors (should be clean)
fsck -t ufs /dev/ad4

* grow filesystem
growfs /dev/ad4

* check again for errors
fsck -t ufs -y /dev/ad4

Result:
You will find tons if not millions of errors. Most will be about the
bogus data in the expanded area. But in a few cases fsck after growfs
destroyed 'original' files as well, deleting over 40% of the original
filesystem.
Comment 1 Nate Eldredge 2007-10-17 08:32:57 UTC
I took a look at this.  Let me say up front that I am not an fs expert, 
I'm just reading the code, so any of this could be wrong.

It looks like this was introduced in revision 1.23 of 
src/sbin/growfs/growfs.c, commited by scottl.  There are actually two 
different bugs for UFS1 and UFS2.

The idea is that inodes have to be initialized to zero before they are 
used, and fsck complains if this isn't the case, even if those inodes are 
not in use according to the cylinder group bitmap.  In UFS1, newfs is 
expected to initialize all inodes.  In UFS2, inode initialization is 
"lazy"; there is a field cg_initediblk in the cylinder group indicating 
how many inodes have been initialized, starting from the first.  (It looks 
like this and cg_niblk count inodes, not blocks, despite the name.)  If 
more are needed, the kernel initializes them as necessary.  For some 
reason, newfs initializes the first two blocks worth of inodes in every 
cg.

growfs works by creating new cylinder groups in the filesystem, each of 
which comes with its own chunk of inodes.  Prior to revision 1.23, growfs 
initialized the inodes in all the cgs it created, for both UFS1 and UFS2. 
Revision 1.23 attempted to optimize this behavior.

For UFS2, it removed the inode initialization completely, but did not 
adjust cg_initediblk accordingly, so the kernel and fsck still thought 
that all inodes were initialized when actually they were not.  My patch 
fixes this by setting cg_initedblk to zero.  It would be possible to 
behave like newfs and initialize the first few inodes, but I don't see why 
that is necessary.  It is simpler to skip it entirely, and in my tests it 
works fine.

For UFS1, revision 1.23 changes it so that all *but* the first two blocks 
of inodes are initialized.  It looks like the author was confused by some 
out-of-context code from newfs (which I'm not sure is exactly right 
itself), since this doesn't make any sense.  My patch changes it back to 
initializing all inodes, and removes some leftover UFS2 initialization 
code as well, which is no longer used.

I tested this patch on a md filesystem, filling it with random bytes, 
creating and filling a 100 MB filesystem, then growing it to 200 MB. 
fsck passes the new filesystem and all files remain intact, with both UFS1 
and UFS2.

--- /usr/src/sbin/growfs/growfs.c	Tue Nov 29 23:20:16 2005
+++ ./growfs.c	Tue Oct 16 23:07:47 2007
@@ -376,7 +376,6 @@
  	long d, dlower, dupper, blkno, start;
  	ufs2_daddr_t i, cbase, dmax;
  	struct ufs1_dinode *dp1;
-	struct ufs2_dinode *dp2;
  	struct csum *cs;

  	if (iobuf == NULL && (iobuf = malloc(sblock.fs_bsize)) == NULL) {
@@ -401,7 +400,7 @@
  	acg.cg_magic = CG_MAGIC;
  	acg.cg_cgx = cylno;
  	acg.cg_niblk = sblock.fs_ipg;
-	acg.cg_initediblk = sblock.fs_ipg;
+	acg.cg_initediblk = 0;
  	acg.cg_ndblk = dmax - cbase;
  	if (sblock.fs_contigsumsize > 0)
  		acg.cg_nclusterblks = acg.cg_ndblk / sblock.fs_frag;
@@ -445,26 +444,16 @@
  			setbit(cg_inosused(&acg), i);
  			acg.cg_cs.cs_nifree--;
  		}
-	/*
-	 * XXX Newfs writes out two blocks of initialized inodes
-	 *     unconditionally.  Should we check here to make sure that they
-	 *     were actually written?
-	 */
  	if (sblock.fs_magic == FS_UFS1_MAGIC) {
  		bzero(iobuf, sblock.fs_bsize);
-		for (i = 2 * sblock.fs_frag; i < sblock.fs_ipg / INOPF(&sblock);
+		for (i = 0; i < sblock.fs_ipg / INOPF(&sblock);
  		     i += sblock.fs_frag) {
  			dp1 = (struct ufs1_dinode *)iobuf;
-			dp2 = (struct ufs2_dinode *)iobuf;
  #ifdef FSIRAND
-			for (j = 0; j < INOPB(&sblock); j++)
-				if (sblock.fs_magic == FS_UFS1_MAGIC) {
-					dp1->di_gen = random();
-					dp1++;
-				} else {
-					dp2->di_gen = random();
-					dp2++;
-				}
+			for (j = 0; j < INOPB(&sblock); j++) {
+				dp1->di_gen = random();
+				dp1++;
+			}
  #endif
  			wtfs(fsbtodb(&sblock, cgimin(&sblock, cylno) + i),
  			    sblock.fs_bsize, iobuf, fso, Nflag);

-- 
Nate Eldredge
nge@cs.hmc.edu
Comment 2 Gavin Atkinson freebsd_committer freebsd_triage 2010-01-01 21:30:09 UTC
Responsible Changed
From-To: freebsd-bugs->gavin

Take.  The UFS2 bug was fixed in r197763, the UFS1 bug can still be recreated on 
HEAD with: 

mdconfig -a -t swap -s 1G 
dd if=/dev/random of=/dev/md0 bs=1048576 
newfs -s 30000 -O 1 /dev/md0 
mount /dev/md0 /mnt 
cp -r /usr/src/sys /mnt 
umount /mnt 
fsck -t ufs /dev/md0 
growfs /dev/md0 
fsck -t ufs /dev/md0
Comment 3 dfilter service freebsd_committer freebsd_triage 2010-02-02 19:51:44 UTC
Author: gavin
Date: Tue Feb  2 19:51:30 2010
New Revision: 203397
URL: http://svn.freebsd.org/changeset/base/203397

Log:
  Merge r201401 from head:
  
    Remove dead code.  This section of code is only run in the
    (sblock.fs_magic == FS_UFS1_MAGIC) case, so the check within the
    loop is redundant.
  
  PR:		bin/115174 (partly)
  Submitted by:	Nate Eldredge  nge cs.hmc.edu
  Reviewed by:	mjacob
  Approved by:	ed (mentor, implicit)

Modified:
  stable/8/sbin/growfs/growfs.c
Directory Properties:
  stable/8/sbin/growfs/   (props changed)

Modified: stable/8/sbin/growfs/growfs.c
==============================================================================
--- stable/8/sbin/growfs/growfs.c	Tue Feb  2 19:44:52 2010	(r203396)
+++ stable/8/sbin/growfs/growfs.c	Tue Feb  2 19:51:30 2010	(r203397)
@@ -376,7 +376,6 @@ initcg(int cylno, time_t utime, int fso,
 	long d, dlower, dupper, blkno, start;
 	ufs2_daddr_t i, cbase, dmax;
 	struct ufs1_dinode *dp1;
-	struct ufs2_dinode *dp2;
 	struct csum *cs;
 
 	if (iobuf == NULL && (iobuf = malloc(sblock.fs_bsize)) == NULL) {
@@ -455,16 +454,11 @@ initcg(int cylno, time_t utime, int fso,
 		for (i = 2 * sblock.fs_frag; i < sblock.fs_ipg / INOPF(&sblock);
 		     i += sblock.fs_frag) {
 			dp1 = (struct ufs1_dinode *)iobuf;
-			dp2 = (struct ufs2_dinode *)iobuf;
 #ifdef FSIRAND
-			for (j = 0; j < INOPB(&sblock); j++)
-				if (sblock.fs_magic == FS_UFS1_MAGIC) {
-					dp1->di_gen = random();
-					dp1++;
-				} else {
-					dp2->di_gen = random();
-					dp2++;
-				}
+			for (j = 0; j < INOPB(&sblock); j++) {
+				dp1->di_gen = random();
+				dp1++;
+			}
 #endif
 			wtfs(fsbtodb(&sblock, cgimin(&sblock, cylno) + i),
 			    sblock.fs_bsize, iobuf, fso, Nflag);
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Comment 4 dfilter service freebsd_committer freebsd_triage 2010-02-13 16:22:23 UTC
Author: gavin
Date: Sat Feb 13 16:22:08 2010
New Revision: 203835
URL: http://svn.freebsd.org/changeset/base/203835

Log:
  When growing a UFS1 filesystem, we need to initialise all inodes in any new
  cylinder groups that are created.  When the filesystem is first created,
  newfs always initialises the first two blocks of inodes, and then in the
  UFS1 case will also initialise the remaining inode blocks.  The changes in
  growfs.c 1.23 broke the initialisation of all inodes, seemingly based on
  this implementation detail in newfs(8).  The result was that instead of
  initialising all inodes, we would actually end up initialising all but the
  first two blocks of inodes.  If the filesystem was grown into empty
  (all-zeros) space then the resulting filesystem was fine, however when
  grown onto non-zeroed space the filesystem produced would appear to have
  massive corruption on the first fsck after growing.
  A test case for this problem can be found in the PR audit trail.
  
  Fix this by once again initialising all inodes in the UFS1 case.
  
  PR:		bin/115174
  Submitted by:	Nate Eldredgei  nge cs.hmc.edu
  Reviewed by:	mjacob
  MFC after:	1 month

Modified:
  head/sbin/growfs/growfs.c

Modified: head/sbin/growfs/growfs.c
==============================================================================
--- head/sbin/growfs/growfs.c	Sat Feb 13 16:04:58 2010	(r203834)
+++ head/sbin/growfs/growfs.c	Sat Feb 13 16:22:08 2010	(r203835)
@@ -450,13 +450,11 @@ initcg(int cylno, time_t utime, int fso,
 			acg.cg_cs.cs_nifree--;
 		}
 	/*
-	 * XXX Newfs writes out two blocks of initialized inodes
-	 *     unconditionally.  Should we check here to make sure that they
-	 *     were actually written?
+	 * For the old file system, we have to initialize all the inodes.
 	 */
 	if (sblock.fs_magic == FS_UFS1_MAGIC) {
 		bzero(iobuf, sblock.fs_bsize);
-		for (i = 2 * sblock.fs_frag; i < sblock.fs_ipg / INOPF(&sblock);
+		for (i = 0; i < sblock.fs_ipg / INOPF(&sblock);
 		     i += sblock.fs_frag) {
 			dp1 = (struct ufs1_dinode *)iobuf;
 #ifdef FSIRAND
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Comment 5 Gavin Atkinson freebsd_committer freebsd_triage 2010-02-13 16:32:42 UTC
State Changed
From-To: open->patched

UFS1 case is fixed in head in r203835.  UFS2 case was fixed in r197763. 
I'm planning on MFCing r203835 in a month.
Comment 6 dfilter service freebsd_committer freebsd_triage 2010-03-17 20:27:45 UTC
Author: gavin
Date: Wed Mar 17 20:27:35 2010
New Revision: 205259
URL: http://svn.freebsd.org/changeset/base/205259

Log:
  Merge r203835 from head:
  
    When growing a UFS1 filesystem, we need to initialise all inodes in any new
    cylinder groups that are created.  When the filesystem is first created,
    newfs always initialises the first two blocks of inodes, and then in the
    UFS1 case will also initialise the remaining inode blocks.  The changes in
    growfs.c 1.23 broke the initialisation of all inodes, seemingly based on
    this implementation detail in newfs(8).  The result was that instead of
    initialising all inodes, we would actually end up initialising all but the
    first two blocks of inodes.  If the filesystem was grown into empty
    (all-zeros) space then the resulting filesystem was fine, however when
    grown onto non-zeroed space the filesystem produced would appear to have
    massive corruption on the first fsck after growing.
    A test case for this problem can be found in the PR audit trail.
  
    Fix this by once again initialising all inodes in the UFS1 case.
  
  PR:		bin/115174
  Submitted by:	"Nate Eldredge"  <nge cs.hmc.edu>
  Reviewed by:	mjacob

Modified:
  stable/8/sbin/growfs/growfs.c
Directory Properties:
  stable/8/sbin/growfs/   (props changed)

Modified: stable/8/sbin/growfs/growfs.c
==============================================================================
--- stable/8/sbin/growfs/growfs.c	Wed Mar 17 20:23:14 2010	(r205258)
+++ stable/8/sbin/growfs/growfs.c	Wed Mar 17 20:27:35 2010	(r205259)
@@ -445,13 +445,11 @@ initcg(int cylno, time_t utime, int fso,
 			acg.cg_cs.cs_nifree--;
 		}
 	/*
-	 * XXX Newfs writes out two blocks of initialized inodes
-	 *     unconditionally.  Should we check here to make sure that they
-	 *     were actually written?
+	 * For the old file system, we have to initialize all the inodes.
 	 */
 	if (sblock.fs_magic == FS_UFS1_MAGIC) {
 		bzero(iobuf, sblock.fs_bsize);
-		for (i = 2 * sblock.fs_frag; i < sblock.fs_ipg / INOPF(&sblock);
+		for (i = 0; i < sblock.fs_ipg / INOPF(&sblock);
 		     i += sblock.fs_frag) {
 			dp1 = (struct ufs1_dinode *)iobuf;
 #ifdef FSIRAND
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Comment 7 dfilter service freebsd_committer freebsd_triage 2010-03-17 20:30:47 UTC
Author: gavin
Date: Wed Mar 17 20:30:37 2010
New Revision: 205260
URL: http://svn.freebsd.org/changeset/base/205260

Log:
  Merge r201401 from head:
  
    Remove dead code.  This section of code is only run in the
    (sblock.fs_magic == FS_UFS1_MAGIC) case, so the check within the
    loop is redundant.
  
  Merge 203835 from head:
  
    When growing a UFS1 filesystem, we need to initialise all inodes in any new
    cylinder groups that are created.  When the filesystem is first created,
    newfs always initialises the first two blocks of inodes, and then in the
    UFS1 case will also initialise the remaining inode blocks.  The changes in
    growfs.c 1.23 broke the initialisation of all inodes, seemingly based on
    this implementation detail in newfs(8).  The result was that instead of
    initialising all inodes, we would actually end up initialising all but the
    first two blocks of inodes.  If the filesystem was grown into empty
    (all-zeros) space then the resulting filesystem was fine, however when
    grown onto non-zeroed space the filesystem produced would appear to have
    massive corruption on the first fsck after growing.
    A test case for this problem can be found in the PR audit trail.
  
    Fix this by once again initialising all inodes in the UFS1 case.
  
  PR:		bin/115174
  Submitted by:	"Nate Eldredge" <nge cs.hmc.edu>
  Reviewed by:	mjacob

Modified:
  stable/7/sbin/growfs/growfs.c
Directory Properties:
  stable/7/sbin/growfs/   (props changed)

Modified: stable/7/sbin/growfs/growfs.c
==============================================================================
--- stable/7/sbin/growfs/growfs.c	Wed Mar 17 20:27:35 2010	(r205259)
+++ stable/7/sbin/growfs/growfs.c	Wed Mar 17 20:30:37 2010	(r205260)
@@ -375,7 +375,6 @@ initcg(int cylno, time_t utime, int fso,
 	long blkno, start;
 	ufs2_daddr_t i, cbase, dmax;
 	struct ufs1_dinode *dp1;
-	struct ufs2_dinode *dp2;
 	struct csum *cs;
 	uint d, dupper, dlower;
 
@@ -446,25 +445,18 @@ initcg(int cylno, time_t utime, int fso,
 			acg.cg_cs.cs_nifree--;
 		}
 	/*
-	 * XXX Newfs writes out two blocks of initialized inodes
-	 *     unconditionally.  Should we check here to make sure that they
-	 *     were actually written?
+	 * For the old file system, we have to initialize all the inodes.
 	 */
 	if (sblock.fs_magic == FS_UFS1_MAGIC) {
 		bzero(iobuf, sblock.fs_bsize);
-		for (i = 2 * sblock.fs_frag; i < sblock.fs_ipg / INOPF(&sblock);
+		for (i = 0; i < sblock.fs_ipg / INOPF(&sblock);
 		     i += sblock.fs_frag) {
 			dp1 = (struct ufs1_dinode *)iobuf;
-			dp2 = (struct ufs2_dinode *)iobuf;
 #ifdef FSIRAND
-			for (j = 0; j < INOPB(&sblock); j++)
-				if (sblock.fs_magic == FS_UFS1_MAGIC) {
-					dp1->di_gen = random();
-					dp1++;
-				} else {
-					dp2->di_gen = random();
-					dp2++;
-				}
+			for (j = 0; j < INOPB(&sblock); j++) {
+				dp1->di_gen = random();
+				dp1++;
+			}
 #endif
 			wtfs(fsbtodb(&sblock, cgimin(&sblock, cylno) + i),
 			    sblock.fs_bsize, iobuf, fso, Nflag);
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Comment 8 Gavin Atkinson freebsd_committer freebsd_triage 2010-03-17 20:32:24 UTC
State Changed
From-To: patched->closed

Fixed in head, and merged to stable/8, stable/7 and stable/6.  Thanks 
for your bug report!
Comment 9 dfilter service freebsd_committer freebsd_triage 2010-03-17 20:32:26 UTC
Author: gavin
Date: Wed Mar 17 20:32:13 2010
New Revision: 205261
URL: http://svn.freebsd.org/changeset/base/205261

Log:
  Merge r201401 from head:
  
    Remove dead code.  This section of code is only run in the
    (sblock.fs_magic == FS_UFS1_MAGIC) case, so the check within the
    loop is redundant.
  
  Merge 203835 from head:
  
    When growing a UFS1 filesystem, we need to initialise all inodes in any new
    cylinder groups that are created.  When the filesystem is first created,
    newfs always initialises the first two blocks of inodes, and then in the
    UFS1 case will also initialise the remaining inode blocks.  The changes in
    growfs.c 1.23 broke the initialisation of all inodes, seemingly based on
    this implementation detail in newfs(8).  The result was that instead of
    initialising all inodes, we would actually end up initialising all but the
    first two blocks of inodes.  If the filesystem was grown into empty
    (all-zeros) space then the resulting filesystem was fine, however when
    grown onto non-zeroed space the filesystem produced would appear to have
    massive corruption on the first fsck after growing.
    A test case for this problem can be found in the PR audit trail.
  
    Fix this by once again initialising all inodes in the UFS1 case.
  
  PR:		bin/115174
  Submitted by:	"Nate Eldredge" <nge cs.hmc.edu>
  Reviewed by:	mjacob

Modified:
  stable/6/sbin/growfs/growfs.c
Directory Properties:
  stable/6/sbin/growfs/   (props changed)

Modified: stable/6/sbin/growfs/growfs.c
==============================================================================
--- stable/6/sbin/growfs/growfs.c	Wed Mar 17 20:30:37 2010	(r205260)
+++ stable/6/sbin/growfs/growfs.c	Wed Mar 17 20:32:13 2010	(r205261)
@@ -376,7 +376,6 @@ initcg(int cylno, time_t utime, int fso,
 	long d, dlower, dupper, blkno, start;
 	ufs2_daddr_t i, cbase, dmax;
 	struct ufs1_dinode *dp1;
-	struct ufs2_dinode *dp2;
 	struct csum *cs;
 
 	if (iobuf == NULL && (iobuf = malloc(sblock.fs_bsize)) == NULL) {
@@ -446,25 +445,18 @@ initcg(int cylno, time_t utime, int fso,
 			acg.cg_cs.cs_nifree--;
 		}
 	/*
-	 * XXX Newfs writes out two blocks of initialized inodes
-	 *     unconditionally.  Should we check here to make sure that they
-	 *     were actually written?
+	 * For the old file system, we have to initialize all the inodes.
 	 */
 	if (sblock.fs_magic == FS_UFS1_MAGIC) {
 		bzero(iobuf, sblock.fs_bsize);
-		for (i = 2 * sblock.fs_frag; i < sblock.fs_ipg / INOPF(&sblock);
+		for (i = 0; i < sblock.fs_ipg / INOPF(&sblock);
 		     i += sblock.fs_frag) {
 			dp1 = (struct ufs1_dinode *)iobuf;
-			dp2 = (struct ufs2_dinode *)iobuf;
 #ifdef FSIRAND
-			for (j = 0; j < INOPB(&sblock); j++)
-				if (sblock.fs_magic == FS_UFS1_MAGIC) {
-					dp1->di_gen = random();
-					dp1++;
-				} else {
-					dp2->di_gen = random();
-					dp2++;
-				}
+			for (j = 0; j < INOPB(&sblock); j++) {
+				dp1->di_gen = random();
+				dp1++;
+			}
 #endif
 			wtfs(fsbtodb(&sblock, cgimin(&sblock, cylno) + i),
 			    sblock.fs_bsize, iobuf, fso, Nflag);
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