[PATCH] ext4: Fix data corruption when writing to prealloc area

[PATCH] ext4: Fix data corruption when writing to prealloc area

[Aneesh Kumar K.V]

We need to recalucate the path information on extent insert
even if depth doesn't change.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/ext4/extents.c |   41 +++++++++++++++++++++++------------------
 1 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 7bdaeec..9c8541e 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2462,7 +2462,10 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 		unsigned int newdepth;
 		/* If extent has less than EXT4_EXT_ZERO_LEN zerout directly */
 		if (allocated <= EXT4_EXT_ZERO_LEN) {
-			/* Mark first half uninitialized.
+			/*
+			 * iblock == ee_block is handled by the zerouout
+			 * at the beginning.
+			 * Mark first half uninitialized.
 			 * Mark second half initialized and zero out the
 			 * initialized extent
 			 */
@@ -2485,7 +2488,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 				ex->ee_len   = orig_ex.ee_len;
 				ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
 				ext4_ext_dirty(handle, inode, path + depth);
-				/* zeroed the full extent */
+				/* blocks available from iblock */
 				return allocated;
 
 			} else if (err)
@@ -2513,6 +2516,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 					err = PTR_ERR(path);
 					return err;
 				}
+				/* get the second half extent details */
 				ex = path[depth].p_ext;
 				err = ext4_ext_get_access(handle, inode,
 								path + depth);
@@ -2542,6 +2546,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
 			ext4_ext_dirty(handle, inode, path + depth);
 			/* zeroed the full extent */
+			/* blocks available from iblock */
 			return allocated;
 
 		} else if (err)
@@ -2557,23 +2562,22 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 		 */
 		orig_ex.ee_len = cpu_to_le16(ee_len -
 						ext4_ext_get_actual_len(ex3));
-		if (newdepth != depth) {
-			depth = newdepth;
-			ext4_ext_drop_refs(path);
-			path = ext4_ext_find_extent(inode, iblock, path);
-			if (IS_ERR(path)) {
-				err = PTR_ERR(path);
-				goto out;
-			}
-			eh = path[depth].p_hdr;
-			ex = path[depth].p_ext;
-			if (ex2 != &newex)
-				ex2 = ex;
-
-			err = ext4_ext_get_access(handle, inode, path + depth);
-			if (err)
-				goto out;
+		depth = newdepth;
+		ext4_ext_drop_refs(path);
+		path = ext4_ext_find_extent(inode, iblock, path);
+		if (IS_ERR(path)) {
+			err = PTR_ERR(path);
+			goto out;
 		}
+		eh = path[depth].p_hdr;
+		ex = path[depth].p_ext;
+		if (ex2 != &newex)
+			ex2 = ex;
+
+		err = ext4_ext_get_access(handle, inode, path + depth);
+		if (err)
+			goto out;
+
 		allocated = max_blocks;
 
 		/* If extent has less than EXT4_EXT_ZERO_LEN and we are trying
@@ -2591,6 +2595,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
 			ext4_ext_dirty(handle, inode, path + depth);
 			/* zero out the first half */
+			/* blocks available from iblock */
 			return allocated;
 		}
 	}
-- 
1.5.6.3.439.g1e10.dirty

Re: [PATCH] ext4: Fix data corruption when writing to prealloc area

[Eric Sandeen]

Aneesh Kumar K.V wrote:
> We need to recalucate the path information on extent insert
> even if depth doesn't change.

Aneesh, do you have a compact test case for this?

Thanks,
-Eric

> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
>  fs/ext4/extents.c |   41 +++++++++++++++++++++++------------------
>  1 files changed, 23 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 7bdaeec..9c8541e 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -2462,7 +2462,10 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  		unsigned int newdepth;
>  		/* If extent has less than EXT4_EXT_ZERO_LEN zerout directly */
>  		if (allocated <= EXT4_EXT_ZERO_LEN) {
> -			/* Mark first half uninitialized.
> +			/*
> +			 * iblock == ee_block is handled by the zerouout
> +			 * at the beginning.
> +			 * Mark first half uninitialized.
>  			 * Mark second half initialized and zero out the
>  			 * initialized extent
>  			 */
> @@ -2485,7 +2488,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  				ex->ee_len   = orig_ex.ee_len;
>  				ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
>  				ext4_ext_dirty(handle, inode, path + depth);
> -				/* zeroed the full extent */
> +				/* blocks available from iblock */
>  				return allocated;
>  
>  			} else if (err)
> @@ -2513,6 +2516,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  					err = PTR_ERR(path);
>  					return err;
>  				}
> +				/* get the second half extent details */
>  				ex = path[depth].p_ext;
>  				err = ext4_ext_get_access(handle, inode,
>  								path + depth);
> @@ -2542,6 +2546,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
>  			ext4_ext_dirty(handle, inode, path + depth);
>  			/* zeroed the full extent */
> +			/* blocks available from iblock */
>  			return allocated;
>  
>  		} else if (err)
> @@ -2557,23 +2562,22 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  		 */
>  		orig_ex.ee_len = cpu_to_le16(ee_len -
>  						ext4_ext_get_actual_len(ex3));
> -		if (newdepth != depth) {
> -			depth = newdepth;
> -			ext4_ext_drop_refs(path);
> -			path = ext4_ext_find_extent(inode, iblock, path);
> -			if (IS_ERR(path)) {
> -				err = PTR_ERR(path);
> -				goto out;
> -			}
> -			eh = path[depth].p_hdr;
> -			ex = path[depth].p_ext;
> -			if (ex2 != &newex)
> -				ex2 = ex;
> -
> -			err = ext4_ext_get_access(handle, inode, path + depth);
> -			if (err)
> -				goto out;
> +		depth = newdepth;
> +		ext4_ext_drop_refs(path);
> +		path = ext4_ext_find_extent(inode, iblock, path);
> +		if (IS_ERR(path)) {
> +			err = PTR_ERR(path);
> +			goto out;
>  		}
> +		eh = path[depth].p_hdr;
> +		ex = path[depth].p_ext;
> +		if (ex2 != &newex)
> +			ex2 = ex;
> +
> +		err = ext4_ext_get_access(handle, inode, path + depth);
> +		if (err)
> +			goto out;
> +
>  		allocated = max_blocks;
>  
>  		/* If extent has less than EXT4_EXT_ZERO_LEN and we are trying
> @@ -2591,6 +2595,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
>  			ext4_ext_dirty(handle, inode, path + depth);
>  			/* zero out the first half */
> +			/* blocks available from iblock */
>  			return allocated;
>  		}
>  	}

Re: [PATCH] ext4: Fix data corruption when writing to prealloc area

[Aneesh Kumar K.V]

On Fri, Jul 18, 2008 at 10:12:46AM -0500, Eric Sandeen wrote:
> Aneesh Kumar K.V wrote:
> > We need to recalucate the path information on extent insert
> > even if depth doesn't change.
> 
> Aneesh, do you have a compact test case for this?
> 


git://github.com/shehjart/tools.git

writefallocate/test.sh

-aneesh

Re: [PATCH] ext4: Fix data corruption when writing to prealloc area

[Mingming Cao]

I tried this patch, with nodelalloc, the kernel did not crash! Previous
it crashes in a few minutes.

 but the test did not stop after fill the file by specified 2G size


I noticed the write() to write to the last fallocate extent(up to 2G)
returns junk value.


The testcase I got from Shehjart (who originally reported the problem)
is  

http://www.gelato.unsw.edu.au/~shehjart/writefallocate.c

command I use to reproduce the problem is 

./writefallocate --filesize 2147483648 --wrblksize 65536 --fallocate
1048576 --filename /mnt/ext4/a --nounlink

.............
offset: 2147024896, written: 65536^M
offset: 2147090432, written: 65536^M
offset: 2147155968, written: 65536^M
offset: 2147221504, written: 65536^M
offset: 2147287040, written: 65536^M
offset: 2147352576, written: 65536^M
offset: 2147418112, written: 65535^M
offset: 2147483647, written: 18446744073709551615^M
fallocate offset: 2147483647^M
offset: 2147483646, written: 18446744073709551615^M
offset: 2147483645, written: 18446744073709551615^M
offset: 2147483644, written: 18446744073709551615^M
offset: 2147483643, written: 18446744073709551615^M
offset: 2147483642, written: 18446744073709551615^M
offset: 2147483641, written: 18446744073709551615^M
offset: 2147483640, written: 18446744073709551615^M


Appearently the test has fallocate/fill the 2G file, but since the last
write() returns 18446744073709551615, the offset is decreased, cause the
test continue with a break,  and writes to wrong offset




在 2008-07-18五的 18:47 +0530，Aneesh Kumar K.V写道：
> We need to recalucate the path information on extent insert
> even if depth doesn't change.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
>  fs/ext4/extents.c |   41 +++++++++++++++++++++++------------------
>  1 files changed, 23 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 7bdaeec..9c8541e 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -2462,7 +2462,10 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  		unsigned int newdepth;
>  		/* If extent has less than EXT4_EXT_ZERO_LEN zerout directly */
>  		if (allocated <= EXT4_EXT_ZERO_LEN) {
> -			/* Mark first half uninitialized.
> +			/*
> +			 * iblock == ee_block is handled by the zerouout
> +			 * at the beginning.
> +			 * Mark first half uninitialized.
>  			 * Mark second half initialized and zero out the
>  			 * initialized extent
>  			 */
> @@ -2485,7 +2488,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  				ex->ee_len   = orig_ex.ee_len;
>  				ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
>  				ext4_ext_dirty(handle, inode, path + depth);
> -				/* zeroed the full extent */
> +				/* blocks available from iblock */
>  				return allocated;
> 
>  			} else if (err)
> @@ -2513,6 +2516,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  					err = PTR_ERR(path);
>  					return err;
>  				}
> +				/* get the second half extent details */
>  				ex = path[depth].p_ext;
>  				err = ext4_ext_get_access(handle, inode,
>  								path + depth);
> @@ -2542,6 +2546,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
>  			ext4_ext_dirty(handle, inode, path + depth);
>  			/* zeroed the full extent */
> +			/* blocks available from iblock */
>  			return allocated;
> 
>  		} else if (err)
> @@ -2557,23 +2562,22 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  		 */
>  		orig_ex.ee_len = cpu_to_le16(ee_len -
>  						ext4_ext_get_actual_len(ex3));
> -		if (newdepth != depth) {
> -			depth = newdepth;
> -			ext4_ext_drop_refs(path);
> -			path = ext4_ext_find_extent(inode, iblock, path);
> -			if (IS_ERR(path)) {
> -				err = PTR_ERR(path);
> -				goto out;
> -			}
> -			eh = path[depth].p_hdr;
> -			ex = path[depth].p_ext;
> -			if (ex2 != &newex)
> -				ex2 = ex;
> -
> -			err = ext4_ext_get_access(handle, inode, path + depth);
> -			if (err)
> -				goto out;
> +		depth = newdepth;
> +		ext4_ext_drop_refs(path);
> +		path = ext4_ext_find_extent(inode, iblock, path);
> +		if (IS_ERR(path)) {
> +			err = PTR_ERR(path);
> +			goto out;
>  		}
> +		eh = path[depth].p_hdr;
> +		ex = path[depth].p_ext;
> +		if (ex2 != &newex)
> +			ex2 = ex;
> +
> +		err = ext4_ext_get_access(handle, inode, path + depth);
> +		if (err)
> +			goto out;
> +
>  		allocated = max_blocks;
> 
>  		/* If extent has less than EXT4_EXT_ZERO_LEN and we are trying
> @@ -2591,6 +2595,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
>  			ext4_ext_dirty(handle, inode, path + depth);
>  			/* zero out the first half */
> +			/* blocks available from iblock */
>  			return allocated;
>  		}
>  	}

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Re: [PATCH] ext4: Fix data corruption when writing to prealloc area

[Mingming Cao]

在 2008-07-18五的 10:02 -0700，Mingming Cao写道：
> I tried this patch, with nodelalloc, the kernel did not crash! Previous
> it crashes in a few minutes.
> 
>  but the test did not stop after fill the file by specified 2G size
> 
> 
> I noticed the write() to write to the last fallocate extent(up to 2G)
> returns junk value.
> 
> 
> The testcase I got from Shehjart (who originally reported the problem)
> is  
> 
> http://www.gelato.unsw.edu.au/~shehjart/writefallocate.c
> 

I forget to mention that I modify the test slight to call fallocate()
with default mode (expnd size) instead of keep size.


> command I use to reproduce the problem is 
> 
> ./writefallocate --filesize 2147483648 --wrblksize 65536 --fallocate
> 1048576 --filename /mnt/ext4/a --nounlink
> 
> .............
> offset: 2147024896, written: 65536^M
> offset: 2147090432, written: 65536^M
> offset: 2147155968, written: 65536^M
> offset: 2147221504, written: 65536^M
> offset: 2147287040, written: 65536^M
> offset: 2147352576, written: 65536^M
> offset: 2147418112, written: 65535^M
> offset: 2147483647, written: 18446744073709551615^M
> fallocate offset: 2147483647^M
> offset: 2147483646, written: 18446744073709551615^M
> offset: 2147483645, written: 18446744073709551615^M
> offset: 2147483644, written: 18446744073709551615^M
> offset: 2147483643, written: 18446744073709551615^M
> offset: 2147483642, written: 18446744073709551615^M
> offset: 2147483641, written: 18446744073709551615^M
> offset: 2147483640, written: 18446744073709551615^M
> 
> 
> Appearently the test has fallocate/fill the 2G file, but since the last
> write() returns 18446744073709551615, the offset is decreased, cause the
> test continue with a break,  and writes to wrong offset
> 
> 
> 
> 
> 在 2008-07-18五的 18:47 +0530，Aneesh Kumar K.V写道：
> > We need to recalucate the path information on extent insert
> > even if depth doesn't change.
> > 
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> > ---
> >  fs/ext4/extents.c |   41 +++++++++++++++++++++++------------------
> >  1 files changed, 23 insertions(+), 18 deletions(-)
> > 
> > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> > index 7bdaeec..9c8541e 100644
> > --- a/fs/ext4/extents.c
> > +++ b/fs/ext4/extents.c
> > @@ -2462,7 +2462,10 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> >  		unsigned int newdepth;
> >  		/* If extent has less than EXT4_EXT_ZERO_LEN zerout directly */
> >  		if (allocated <= EXT4_EXT_ZERO_LEN) {
> > -			/* Mark first half uninitialized.
> > +			/*
> > +			 * iblock == ee_block is handled by the zerouout
> > +			 * at the beginning.
> > +			 * Mark first half uninitialized.
> >  			 * Mark second half initialized and zero out the
> >  			 * initialized extent
> >  			 */
> > @@ -2485,7 +2488,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> >  				ex->ee_len   = orig_ex.ee_len;
> >  				ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
> >  				ext4_ext_dirty(handle, inode, path + depth);
> > -				/* zeroed the full extent */
> > +				/* blocks available from iblock */
> >  				return allocated;
> > 
> >  			} else if (err)
> > @@ -2513,6 +2516,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> >  					err = PTR_ERR(path);
> >  					return err;
> >  				}
> > +				/* get the second half extent details */
> >  				ex = path[depth].p_ext;
> >  				err = ext4_ext_get_access(handle, inode,
> >  								path + depth);
> > @@ -2542,6 +2546,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> >  			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
> >  			ext4_ext_dirty(handle, inode, path + depth);
> >  			/* zeroed the full extent */
> > +			/* blocks available from iblock */
> >  			return allocated;
> > 
> >  		} else if (err)
> > @@ -2557,23 +2562,22 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> >  		 */
> >  		orig_ex.ee_len = cpu_to_le16(ee_len -
> >  						ext4_ext_get_actual_len(ex3));
> > -		if (newdepth != depth) {
> > -			depth = newdepth;
> > -			ext4_ext_drop_refs(path);
> > -			path = ext4_ext_find_extent(inode, iblock, path);
> > -			if (IS_ERR(path)) {
> > -				err = PTR_ERR(path);
> > -				goto out;
> > -			}
> > -			eh = path[depth].p_hdr;
> > -			ex = path[depth].p_ext;
> > -			if (ex2 != &newex)
> > -				ex2 = ex;
> > -
> > -			err = ext4_ext_get_access(handle, inode, path + depth);
> > -			if (err)
> > -				goto out;
> > +		depth = newdepth;
> > +		ext4_ext_drop_refs(path);
> > +		path = ext4_ext_find_extent(inode, iblock, path);
> > +		if (IS_ERR(path)) {
> > +			err = PTR_ERR(path);
> > +			goto out;
> >  		}
> > +		eh = path[depth].p_hdr;
> > +		ex = path[depth].p_ext;
> > +		if (ex2 != &newex)
> > +			ex2 = ex;
> > +
> > +		err = ext4_ext_get_access(handle, inode, path + depth);
> > +		if (err)
> > +			goto out;
> > +
> >  		allocated = max_blocks;
> > 
> >  		/* If extent has less than EXT4_EXT_ZERO_LEN and we are trying
> > @@ -2591,6 +2595,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> >  			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
> >  			ext4_ext_dirty(handle, inode, path + depth);
> >  			/* zero out the first half */
> > +			/* blocks available from iblock */
> >  			return allocated;
> >  		}
> >  	}
> 
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Re: [PATCH] ext4: Fix data corruption when writing to prealloc area

[Mingming Cao]

在 2008-07-18五的 10:22 -0700，Mingming Cao写道：
> 在 2008-07-18五的 10:02 -0700，Mingming Cao写道：
> > I tried this patch, with nodelalloc, the kernel did not crash! Previous
> > it crashes in a few minutes.
> > 
> >  but the test did not stop after fill the file by specified 2G size
> > 
> > 
> > I noticed the write() to write to the last fallocate extent(up to 2G)
> > returns junk value.
> > 
> > 
> > The testcase I got from Shehjart (who originally reported the problem)
> > is  
> > 
> > http://www.gelato.unsw.edu.au/~shehjart/writefallocate.c
> > 
> 
> I forget to mention that I modify the test slight to call fallocate()
> with default mode (expnd size) instead of keep size.
> 

Oh, it's the file size problem for the 2 GB barrier, the latest test
source git tree  has fixed this,.  With the patch ext4 runs fine with
both KEEP_SIZE mode and ALLOCATE mode.

Mingming

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Re: [PATCH] ext4: Fix data corruption when writing to prealloc area

[Mingming Cao]

在 2008-07-18五的 18:47 +0530，Aneesh Kumar K.V写道：
> We need to recalucate the path information on extent insert
> even if depth doesn't change.
> 

Patch has been added to ext4 patch queue

Acked-by: Mingming Cao <cmm@us.ibm.com>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
>  fs/ext4/extents.c |   41 +++++++++++++++++++++++------------------
>  1 files changed, 23 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 7bdaeec..9c8541e 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -2462,7 +2462,10 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  		unsigned int newdepth;
>  		/* If extent has less than EXT4_EXT_ZERO_LEN zerout directly */
>  		if (allocated <= EXT4_EXT_ZERO_LEN) {
> -			/* Mark first half uninitialized.
> +			/*
> +			 * iblock == ee_block is handled by the zerouout
> +			 * at the beginning.
> +			 * Mark first half uninitialized.
>  			 * Mark second half initialized and zero out the
>  			 * initialized extent
>  			 */
> @@ -2485,7 +2488,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  				ex->ee_len   = orig_ex.ee_len;
>  				ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
>  				ext4_ext_dirty(handle, inode, path + depth);
> -				/* zeroed the full extent */
> +				/* blocks available from iblock */
>  				return allocated;
> 
>  			} else if (err)
> @@ -2513,6 +2516,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  					err = PTR_ERR(path);
>  					return err;
>  				}
> +				/* get the second half extent details */
>  				ex = path[depth].p_ext;
>  				err = ext4_ext_get_access(handle, inode,
>  								path + depth);
> @@ -2542,6 +2546,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
>  			ext4_ext_dirty(handle, inode, path + depth);
>  			/* zeroed the full extent */
> +			/* blocks available from iblock */
>  			return allocated;
> 
>  		} else if (err)
> @@ -2557,23 +2562,22 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  		 */
>  		orig_ex.ee_len = cpu_to_le16(ee_len -
>  						ext4_ext_get_actual_len(ex3));
> -		if (newdepth != depth) {
> -			depth = newdepth;
> -			ext4_ext_drop_refs(path);
> -			path = ext4_ext_find_extent(inode, iblock, path);
> -			if (IS_ERR(path)) {
> -				err = PTR_ERR(path);
> -				goto out;
> -			}
> -			eh = path[depth].p_hdr;
> -			ex = path[depth].p_ext;
> -			if (ex2 != &newex)
> -				ex2 = ex;
> -
> -			err = ext4_ext_get_access(handle, inode, path + depth);
> -			if (err)
> -				goto out;
> +		depth = newdepth;
> +		ext4_ext_drop_refs(path);
> +		path = ext4_ext_find_extent(inode, iblock, path);
> +		if (IS_ERR(path)) {
> +			err = PTR_ERR(path);
> +			goto out;
>  		}
> +		eh = path[depth].p_hdr;
> +		ex = path[depth].p_ext;
> +		if (ex2 != &newex)
> +			ex2 = ex;
> +
> +		err = ext4_ext_get_access(handle, inode, path + depth);
> +		if (err)
> +			goto out;
> +
>  		allocated = max_blocks;
> 
>  		/* If extent has less than EXT4_EXT_ZERO_LEN and we are trying
> @@ -2591,6 +2595,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
>  			ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
>  			ext4_ext_dirty(handle, inode, path + depth);
>  			/* zero out the first half */
> +			/* blocks available from iblock */
>  			return allocated;
>  		}
>  	}

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