ext4: fix infinite loop when replaying fast_commit

When doing fast_commit replay an infinite loop may occur due to an uninitialized extent_status struct. ext4_ext_determine_insert_hole() does not detect the replay and calls ext4_es_find_extent_range(), which will return immediately without initializing the 'es' variable.

Because 'es' contains garbage, an integer overflow may happen causing an infinite loop in this function, easily reproducible using fstest generic/039.

This commit fixes this issue by detecting the replay in function ext4_ext_determine_insert_hole(). It also adds initialization code to the error path in function ext4_es_find_extent_range().

Thanks to Zhang Yi, for figuring out the real problem!

Fixes 8016e29f4362 ("ext4: fast commit recovery path")

Signed-off-by Luis Henriques (SUSE) <[email protected]>

---
Hi!

Two comments:
1) The change in ext4_ext_map_blocks() could probably use the min_not_zero macro instead. I decided not to do so simply because I wasn't sure if that would be safe, but I'm fine changing that if you think it is.

2) I thought about returning 'EXT_MAX_BLOCKS' instead of '0' in ext4_lblk_t ext4_ext_determine_insert_hole(), which would then avoid the extra change to ext4_ext_map_blocks(). '0' sounds like the right value to return, but I'm also OK using 'EXT_MAX_BLOCKS' instead.

And again thanks to Zhang Yi for pointing me the *real* problem!

 fs/ext4/extents.c        | 6 +++++-
 fs/ext4/extents_status.c | 5 ++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

fs/ext4/extents.c +0 -0

index e57054bdc5fd..b5bfcb6c18a0 100644

fs/ext4/extents.c +2 -1

 	hole_start = lblk;
 	len = ext4_ext_find_hole(inode, path, &hole_start);
 again:

@@ -4226,7 +4229,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 		len = ext4_ext_determine_insert_hole(inode, path, map->m_lblk);
 
 		map->m_pblk = 0;
-		map->m_len = min_t(unsigned int, map->m_len, len);
+		if (len > 0)
+			map->m_len = min_t(unsigned int, map->m_len, len);
 		goto out;
 	}
 

fs/ext4/extents_status.c +4 -1

index 4a00e2f019d9..acb9616ca119 100644
@@ -310,8 +310,11 @@ void ext4_es_find_extent_range(struct inode *inode,
 			       ext4_lblk_t lblk, ext4_lblk_t end,
 			       struct extent_status *es)
 {
-	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
+	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) {
+		/* Initialize extent to zero */
+		es->es_lblk = es->es_len = es->es_pblk = 0;
 		return;
+	}
 
 	trace_ext4_es_find_extent_range_enter(inode, lblk);
 

Quoted 43 lines

When doing fast_commit replay an infinite loop may occur due to an uninitialized extent_status struct. ext4_ext_determine_insert_hole() does not detect the replay and calls ext4_es_find_extent_range(), which will return immediately without initializing the 'es' variable.

Because 'es' contains garbage, an integer overflow may happen causing an infinite loop in this function, easily reproducible using fstest generic/039.

This commit fixes this issue by detecting the replay in function ext4_ext_determine_insert_hole(). It also adds initialization code to the error path in function ext4_es_find_extent_range().

Thanks to Zhang Yi, for figuring out the real problem!

Fixes 8016e29f4362 ("ext4: fast commit recovery path")

Signed-off-by Luis Henriques (SUSE) <[email protected]>

---
Hi!

Two comments:
1) The change in ext4_ext_map_blocks() could probably use the min_not_zero macro instead. I decided not to do so simply because I wasn't sure if that would be safe, but I'm fine changing that if you think it is.

2) I thought about returning 'EXT_MAX_BLOCKS' instead of '0' in ext4_lblk_t ext4_ext_determine_insert_hole(), which would then avoid the extra change to ext4_ext_map_blocks(). '0' sounds like the right value to return, but I'm also OK using 'EXT_MAX_BLOCKS' instead.

And again thanks to Zhang Yi for pointing me the *real* problem!

 fs/ext4/extents.c        | 6 +++++-
 fs/ext4/extents_status.c | 5 ++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

fs/ext4/extents.c +0 -0

index e57054bdc5fd..b5bfcb6c18a0 100644
@@ -4052,6 +4052,9 @@ static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode,
 	ext4_lblk_t hole_start, len;
 	struct extent_status es;
 

fs/ext4/extents.c static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode, · line 4057

Quoted 3 lines

fs/ext4/extents.c +3 -0

+	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
+		return 0;
+

Sorry, I think it's may not correct. When replaying the jouranl, although we don't use the extent statue tree, we still need to query the accurate hole length, e.g. please see skip_hole(). If you do this, the hole length becomes incorrect, right?

Thanks,
Yi.

Quoted 31 lines

fs/ext4/extents.c +2 -1

 	hole_start = lblk;
 	len = ext4_ext_find_hole(inode, path, &hole_start);
 again:

@@ -4226,7 +4229,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
 		len = ext4_ext_determine_insert_hole(inode, path, map->m_lblk);
 
 		map->m_pblk = 0;
-		map->m_len = min_t(unsigned int, map->m_len, len);
+		if (len > 0)
+			map->m_len = min_t(unsigned int, map->m_len, len);
 		goto out;
 	}
 

fs/ext4/extents_status.c +4 -1

index 4a00e2f019d9..acb9616ca119 100644
@@ -310,8 +310,11 @@ void ext4_es_find_extent_range(struct inode *inode,
 			       ext4_lblk_t lblk, ext4_lblk_t end,
 			       struct extent_status *es)
 {
-	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
+	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) {
+		/* Initialize extent to zero */
+		es->es_lblk = es->es_len = es->es_pblk = 0;
 		return;
+	}
 
 	trace_ext4_es_find_extent_range_enter(inode, lblk);
 

On Sat 11 May 2024 02:24:17 PM +08, Zhang Yi wrote;

Quoted 44 lines · Luis Henriques (SUSE)

Quoted 43 lines

When doing fast_commit replay an infinite loop may occur due to an uninitialized extent_status struct. ext4_ext_determine_insert_hole() does not detect the replay and calls ext4_es_find_extent_range(), which will return immediately without initializing the 'es' variable.

Because 'es' contains garbage, an integer overflow may happen causing an infinite loop in this function, easily reproducible using fstest generic/039.

This commit fixes this issue by detecting the replay in function ext4_ext_determine_insert_hole(). It also adds initialization code to the error path in function ext4_es_find_extent_range().

Thanks to Zhang Yi, for figuring out the real problem!

Fixes 8016e29f4362 ("ext4: fast commit recovery path")

Signed-off-by Luis Henriques (SUSE) <[email protected]>

---
Hi!

Two comments:
1) The change in ext4_ext_map_blocks() could probably use the min_not_zero macro instead. I decided not to do so simply because I wasn't sure if that would be safe, but I'm fine changing that if you think it is.

2) I thought about returning 'EXT_MAX_BLOCKS' instead of '0' in ext4_lblk_t ext4_ext_determine_insert_hole(), which would then avoid the extra change to ext4_ext_map_blocks(). '0' sounds like the right value to return, but I'm also OK using 'EXT_MAX_BLOCKS' instead.

And again thanks to Zhang Yi for pointing me the *real* problem!

 fs/ext4/extents.c        | 6 +++++-
 fs/ext4/extents_status.c | 5 ++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

fs/ext4/extents.c +0 -0

index e57054bdc5fd..b5bfcb6c18a0 100644
@@ -4052,6 +4052,9 @@ static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode,
 	ext4_lblk_t hole_start, len;
 	struct extent_status es;
 

Quoted 8 lines

fs/ext4/extents.c static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode, · line 4057

Quoted 3 lines

fs/ext4/extents.c +3 -0

+	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
+		return 0;
+

Sorry, I think it's may not correct. When replaying the jouranl, although we don't use the extent statue tree, we still need to query the accurate hole length, e.g. please see skip_hole(). If you do this, the hole length becomes incorrect, right?

Thank you for your review (and sorry for my delay replying).

So, I see three different options to follow your suggestion:

1) Initialize 'es' immediately when declaring it in function ext4_ext_determine_insert_hole():

	es.es_lblk = es.es_len = es.es_pblk = 0;

2) Initialize 'es' only in ext4_es_find_extent_range() when checking if an fc replay is in progress (my patch was already doing something like that):

	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) {
		/* Initialize extent to zero */
		es->es_lblk = es->es_len = es->es_pblk = 0;
		return;
	}

3) Remove the check for fc replay in function ext4_es_find_extent_range(), which will then unconditionally call __es_find_extent_range(). This will effectively also initialize the 'es' fields to '0' and, because __es_tree_search() will return NULL (at least in generic/039 test!), nothing else will be done.

Since all these 3 options seem to have the same result, I believe option
1) is probably the best as it initializes the structure shortly after it's declaration. Would you agree? Or did I misunderstood you?

Quoted 80 lines

On Sat 11 May 2024 02:24:17 PM +08, Zhang Yi wrote;

Quoted 44 lines · Luis Henriques (SUSE)

Quoted 43 lines

When doing fast_commit replay an infinite loop may occur due to an uninitialized extent_status struct. ext4_ext_determine_insert_hole() does not detect the replay and calls ext4_es_find_extent_range(), which will return immediately without initializing the 'es' variable.

Because 'es' contains garbage, an integer overflow may happen causing an infinite loop in this function, easily reproducible using fstest generic/039.

This commit fixes this issue by detecting the replay in function ext4_ext_determine_insert_hole(). It also adds initialization code to the error path in function ext4_es_find_extent_range().

Thanks to Zhang Yi, for figuring out the real problem!

Fixes 8016e29f4362 ("ext4: fast commit recovery path")

Signed-off-by Luis Henriques (SUSE) <[email protected]>

---
Hi!

Two comments:
1) The change in ext4_ext_map_blocks() could probably use the min_not_zero macro instead. I decided not to do so simply because I wasn't sure if that would be safe, but I'm fine changing that if you think it is.

2) I thought about returning 'EXT_MAX_BLOCKS' instead of '0' in ext4_lblk_t ext4_ext_determine_insert_hole(), which would then avoid the extra change to ext4_ext_map_blocks(). '0' sounds like the right value to return, but I'm also OK using 'EXT_MAX_BLOCKS' instead.

And again thanks to Zhang Yi for pointing me the *real* problem!

 fs/ext4/extents.c        | 6 +++++-
 fs/ext4/extents_status.c | 5 ++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

fs/ext4/extents.c +0 -0

index e57054bdc5fd..b5bfcb6c18a0 100644
@@ -4052,6 +4052,9 @@ static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode,
 	ext4_lblk_t hole_start, len;
 	struct extent_status es;
 

Quoted 8 lines

fs/ext4/extents.c static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode, · line 4057

Quoted 3 lines

fs/ext4/extents.c +3 -0

+	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
+		return 0;
+

Sorry, I think it's may not correct. When replaying the jouranl, although we don't use the extent statue tree, we still need to query the accurate hole length, e.g. please see skip_hole(). If you do this, the hole length becomes incorrect, right?

Thank you for your review (and sorry for my delay replying).

So, I see three different options to follow your suggestion:

1) Initialize 'es' immediately when declaring it in function ext4_ext_determine_insert_hole():

	es.es_lblk = es.es_len = es.es_pblk = 0;

2) Initialize 'es' only in ext4_es_find_extent_range() when checking if an fc replay is in progress (my patch was already doing something like that):

	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) {
		/* Initialize extent to zero */
		es->es_lblk = es->es_len = es->es_pblk = 0;
		return;
	}

3) Remove the check for fc replay in function ext4_es_find_extent_range(), which will then unconditionally call __es_find_extent_range(). This will effectively also initialize the 'es' fields to '0' and, because __es_tree_search() will return NULL (at least in generic/039 test!), nothing else will be done.

Quoted 4 lines

Since all these 3 options seem to have the same result, I believe option
1) is probably the best as it initializes the structure shortly after it's declaration. Would you agree? Or did I misunderstood you?

Both 1 and 2 are looks fine to me, but I would prefer to initialize it unconditionally in ext4_es_find_extent_range().

On Wed 15 May 2024 12:59:26 PM +08, Zhang Yi wrote;

Quoted 89 lines · Luis Henriques

Quoted 80 lines

On Sat 11 May 2024 02:24:17 PM +08, Zhang Yi wrote;

Quoted 44 lines · Luis Henriques (SUSE)

Quoted 43 lines

When doing fast_commit replay an infinite loop may occur due to an uninitialized extent_status struct. ext4_ext_determine_insert_hole() does not detect the replay and calls ext4_es_find_extent_range(), which will return immediately without initializing the 'es' variable.

Because 'es' contains garbage, an integer overflow may happen causing an infinite loop in this function, easily reproducible using fstest generic/039.

This commit fixes this issue by detecting the replay in function ext4_ext_determine_insert_hole(). It also adds initialization code to the error path in function ext4_es_find_extent_range().

Thanks to Zhang Yi, for figuring out the real problem!

Fixes 8016e29f4362 ("ext4: fast commit recovery path")

Signed-off-by Luis Henriques (SUSE) <[email protected]>

---
Hi!

Two comments:
1) The change in ext4_ext_map_blocks() could probably use the min_not_zero macro instead. I decided not to do so simply because I wasn't sure if that would be safe, but I'm fine changing that if you think it is.

2) I thought about returning 'EXT_MAX_BLOCKS' instead of '0' in ext4_lblk_t ext4_ext_determine_insert_hole(), which would then avoid the extra change to ext4_ext_map_blocks(). '0' sounds like the right value to return, but I'm also OK using 'EXT_MAX_BLOCKS' instead.

And again thanks to Zhang Yi for pointing me the *real* problem!

 fs/ext4/extents.c        | 6 +++++-
 fs/ext4/extents_status.c | 5 ++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

fs/ext4/extents.c +0 -0

index e57054bdc5fd..b5bfcb6c18a0 100644
@@ -4052,6 +4052,9 @@ static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode,
 	ext4_lblk_t hole_start, len;
 	struct extent_status es;
 

Quoted 8 lines

fs/ext4/extents.c static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode, · line 4057

Quoted 3 lines

fs/ext4/extents.c +3 -0

+	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
+		return 0;
+

Sorry, I think it's may not correct. When replaying the jouranl, although we don't use the extent statue tree, we still need to query the accurate hole length, e.g. please see skip_hole(). If you do this, the hole length becomes incorrect, right?

Thank you for your review (and sorry for my delay replying).

So, I see three different options to follow your suggestion:

1) Initialize 'es' immediately when declaring it in function ext4_ext_determine_insert_hole():

	es.es_lblk = es.es_len = es.es_pblk = 0;

2) Initialize 'es' only in ext4_es_find_extent_range() when checking if an fc replay is in progress (my patch was already doing something like that):

	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) {
		/* Initialize extent to zero */
		es->es_lblk = es->es_len = es->es_pblk = 0;
		return;
	}

3) Remove the check for fc replay in function ext4_es_find_extent_range(), which will then unconditionally call __es_find_extent_range(). This will effectively also initialize the 'es' fields to '0' and, because __es_tree_search() will return NULL (at least in generic/039 test!), nothing else will be done.

Quoted 4 lines

Since all these 3 options seem to have the same result, I believe option
1) is probably the best as it initializes the structure shortly after it's declaration. Would you agree? Or did I misunderstood you?

Both 1 and 2 are looks fine to me, but I would prefer to initialize it unconditionally in ext4_es_find_extent_range().

fs/ext4/extents_status.c void ext4_es_find_extent_range(struct inode *inode, · line 316

Quoted 8 lines

fs/ext4/extents_status.c +2 -0

@@ -310,6 +310,8 @@ void ext4_es_find_extent_range(struct inode *inode,
 				ext4_lblk_t lblk, ext4_lblk_t end,
 				struct extent_status *es)
 {
+	es->es_lblk = es->es_len = es->es_pblk = 0;
+
 	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
 		return;

Thank you, Yi. I'll send out v2 shortly. Although, to be fair, the real patch author shouldn't be me. :-)

Quoted 91 lines

On Wed 15 May 2024 12:59:26 PM +08, Zhang Yi wrote;

Quoted 89 lines · Luis Henriques

Quoted 80 lines

On Sat 11 May 2024 02:24:17 PM +08, Zhang Yi wrote;

Quoted 44 lines · Luis Henriques (SUSE)

Quoted 43 lines

When doing fast_commit replay an infinite loop may occur due to an uninitialized extent_status struct. ext4_ext_determine_insert_hole() does not detect the replay and calls ext4_es_find_extent_range(), which will return immediately without initializing the 'es' variable.

Because 'es' contains garbage, an integer overflow may happen causing an infinite loop in this function, easily reproducible using fstest generic/039.

This commit fixes this issue by detecting the replay in function ext4_ext_determine_insert_hole(). It also adds initialization code to the error path in function ext4_es_find_extent_range().

Thanks to Zhang Yi, for figuring out the real problem!

Fixes 8016e29f4362 ("ext4: fast commit recovery path")

Signed-off-by Luis Henriques (SUSE) <[email protected]>

---
Hi!

Two comments:
1) The change in ext4_ext_map_blocks() could probably use the min_not_zero macro instead. I decided not to do so simply because I wasn't sure if that would be safe, but I'm fine changing that if you think it is.

2) I thought about returning 'EXT_MAX_BLOCKS' instead of '0' in ext4_lblk_t ext4_ext_determine_insert_hole(), which would then avoid the extra change to ext4_ext_map_blocks(). '0' sounds like the right value to return, but I'm also OK using 'EXT_MAX_BLOCKS' instead.

And again thanks to Zhang Yi for pointing me the *real* problem!

 fs/ext4/extents.c        | 6 +++++-
 fs/ext4/extents_status.c | 5 ++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

fs/ext4/extents.c +0 -0

index e57054bdc5fd..b5bfcb6c18a0 100644
@@ -4052,6 +4052,9 @@ static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode,
 	ext4_lblk_t hole_start, len;
 	struct extent_status es;
 

Quoted 8 lines

fs/ext4/extents.c static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode, · line 4057

Quoted 3 lines

fs/ext4/extents.c +3 -0

+	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
+		return 0;
+

Sorry, I think it's may not correct. When replaying the jouranl, although we don't use the extent statue tree, we still need to query the accurate hole length, e.g. please see skip_hole(). If you do this, the hole length becomes incorrect, right?

Thank you for your review (and sorry for my delay replying).

So, I see three different options to follow your suggestion:

1) Initialize 'es' immediately when declaring it in function ext4_ext_determine_insert_hole():

	es.es_lblk = es.es_len = es.es_pblk = 0;

2) Initialize 'es' only in ext4_es_find_extent_range() when checking if an fc replay is in progress (my patch was already doing something like that):

	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) {
		/* Initialize extent to zero */
		es->es_lblk = es->es_len = es->es_pblk = 0;
		return;
	}

3) Remove the check for fc replay in function ext4_es_find_extent_range(), which will then unconditionally call __es_find_extent_range(). This will effectively also initialize the 'es' fields to '0' and, because __es_tree_search() will return NULL (at least in generic/039 test!), nothing else will be done.

Quoted 4 lines

Since all these 3 options seem to have the same result, I believe option
1) is probably the best as it initializes the structure shortly after it's declaration. Would you agree? Or did I misunderstood you?

Both 1 and 2 are looks fine to me, but I would prefer to initialize it unconditionally in ext4_es_find_extent_range().

Quoted 12 lines

fs/ext4/extents_status.c void ext4_es_find_extent_range(struct inode *inode, · line 316

Quoted 8 lines

fs/ext4/extents_status.c +2 -0

@@ -310,6 +310,8 @@ void ext4_es_find_extent_range(struct inode *inode,
 				ext4_lblk_t lblk, ext4_lblk_t end,
 				struct extent_status *es)
 {
+	es->es_lblk = es->es_len = es->es_pblk = 0;
+
 	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
 		return;

Thank you, Yi. I'll send out v2 shortly. Although, to be fair, the real patch author shouldn't be me. :-)

Never mind, I just give a suggestion and also I didn't do a full test on this change.

On Wed 15 May 2024 04:52:54 PM +08, Zhang Yi wrote;

Quoted 105 lines · Luis Henriques

Quoted 103 lines

On Wed 15 May 2024 12:59:26 PM +08, Zhang Yi wrote;

Quoted 90 lines · Luis Henriques

Quoted 80 lines

On Sat 11 May 2024 02:24:17 PM +08, Zhang Yi wrote;

Quoted 44 lines · Luis Henriques (SUSE)

Quoted 43 lines

When doing fast_commit replay an infinite loop may occur due to an uninitialized extent_status struct. ext4_ext_determine_insert_hole() does not detect the replay and calls ext4_es_find_extent_range(), which will return immediately without initializing the 'es' variable.

Because 'es' contains garbage, an integer overflow may happen causing an infinite loop in this function, easily reproducible using fstest generic/039.

This commit fixes this issue by detecting the replay in function ext4_ext_determine_insert_hole(). It also adds initialization code to the error path in function ext4_es_find_extent_range().

Thanks to Zhang Yi, for figuring out the real problem!

Fixes 8016e29f4362 ("ext4: fast commit recovery path")

Signed-off-by Luis Henriques (SUSE) <[email protected]>

---
Hi!

Two comments:
1) The change in ext4_ext_map_blocks() could probably use the min_not_zero macro instead. I decided not to do so simply because I wasn't sure if that would be safe, but I'm fine changing that if you think it is.

2) I thought about returning 'EXT_MAX_BLOCKS' instead of '0' in ext4_lblk_t ext4_ext_determine_insert_hole(), which would then avoid the extra change to ext4_ext_map_blocks(). '0' sounds like the right value to return, but I'm also OK using 'EXT_MAX_BLOCKS' instead.

And again thanks to Zhang Yi for pointing me the *real* problem!

 fs/ext4/extents.c        | 6 +++++-
 fs/ext4/extents_status.c | 5 ++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

fs/ext4/extents.c +0 -0

index e57054bdc5fd..b5bfcb6c18a0 100644
@@ -4052,6 +4052,9 @@ static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode,
 	ext4_lblk_t hole_start, len;
 	struct extent_status es;
 

Quoted 8 lines

fs/ext4/extents.c static ext4_lblk_t ext4_ext_determine_insert_hole(struct inode *inode, · line 4057

Quoted 3 lines

fs/ext4/extents.c +3 -0

+	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
+		return 0;
+

Sorry, I think it's may not correct. When replaying the jouranl, although we don't use the extent statue tree, we still need to query the accurate hole length, e.g. please see skip_hole(). If you do this, the hole length becomes incorrect, right?

Thank you for your review (and sorry for my delay replying).

So, I see three different options to follow your suggestion:

1) Initialize 'es' immediately when declaring it in function ext4_ext_determine_insert_hole():

	es.es_lblk = es.es_len = es.es_pblk = 0;

2) Initialize 'es' only in ext4_es_find_extent_range() when checking if an fc replay is in progress (my patch was already doing something like that):

	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY) {
		/* Initialize extent to zero */
		es->es_lblk = es->es_len = es->es_pblk = 0;
		return;
	}

3) Remove the check for fc replay in function ext4_es_find_extent_range(), which will then unconditionally call __es_find_extent_range(). This will effectively also initialize the 'es' fields to '0' and, because __es_tree_search() will return NULL (at least in generic/039 test!), nothing else will be done.

Quoted 4 lines

Since all these 3 options seem to have the same result, I believe option
1) is probably the best as it initializes the structure shortly after it's declaration. Would you agree? Or did I misunderstood you?

Both 1 and 2 are looks fine to me, but I would prefer to initialize it unconditionally in ext4_es_find_extent_range().

Review void ext4_es_find_extent_range(struct inode *inode, · line 316

Quoted 7 lines

(quoted diff) +2 -0

@@ -310,6 +310,8 @@ void ext4_es_find_extent_range(struct inode *inode,
 				ext4_lblk_t lblk, ext4_lblk_t end,
 				struct extent_status *es)
 {
+	es->es_lblk = es->es_len = es->es_pblk = 0;
+
 	if (EXT4_SB(inode->i_sb)->s_mount_state & EXT4_FC_REPLAY)
 		return;

Thank you, Yi. I'll send out v2 shortly. Although, to be fair, the real patch author shouldn't be me. :-)

Quoted 2 lines

Never mind, I just give a suggestion and also I didn't do a full test on this change.

Oh, talking about testing, I forgot to mention that I see the same behaviour with generic/311. I.e. this test also enters an infinite loop, but fixed with this patch.

This commit fixes this issue by detecting the replay …

Thanks to Zhang Yi, for figuring out the real problem!