[PATCH 0/2] read-cache: two small leak fixes

[PATCH 0/2] read-cache: two small leak fixes

[Derrick Stolee via GitGitGadget]

I found these two small memory leaks while investigating things involving
the index. I thought they were small enough to send independently.

I initially wrote this as two patches because the second patch was more
involved to work around the "cleanup" label, and my branch was based on
2.46.1. This code has changed recently due to d1c53f6703 (read-cache: fix
leaking hashfile when writing index fails, 2024-08-14), so now the second
patch is simpler and these could probably be merged into one.

Thanks, -Stolee

Derrick Stolee (2):
  read-cache: free threaded memory pool
  read-cache: free hash context in do_write_index()

 read-cache.c | 2 ++
 1 file changed, 2 insertions(+)


base-commit: 6258f68c3c1092c901337895c864073dcdea9213
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1801%2Fderrickstolee%2Fleaks-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1801/derrickstolee/leaks-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1801
-- 
gitgitgadget

[PATCH 1/2] read-cache: free threaded memory pool

[Derrick Stolee via GitGitGadget]

From: Derrick Stolee <stolee@gmail.com>

In load_cache_entries_threaded(), each thread is allocated its own
memory pool. This pool needs to be cleaned up while closing the threads
down, or it will be leaked.

Signed-off-by: Derrick Stolee <stolee@gmail.com>
---
 read-cache.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/read-cache.c b/read-cache.c
index 764fdfec465..3c078afadbc 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -2188,6 +2188,7 @@ static unsigned long load_cache_entries_threaded(struct index_state *istate, con
 		if (err)
 			die(_("unable to join load_cache_entries thread: %s"), strerror(err));
 		mem_pool_combine(istate->ce_mem_pool, p->ce_mem_pool);
+		free(p->ce_mem_pool);
 		consumed += p->consumed;
 	}
 
-- 
gitgitgadget

[PATCH 2/2] read-cache: free hash context in do_write_index()

[Derrick Stolee via GitGitGadget]

From: Derrick Stolee <stolee@gmail.com>

While writing an index, a 'git_hash_ctx' is allocated for hashing the
file contents. This should be freed as the method exits.

Signed-off-by: Derrick Stolee <stolee@gmail.com>
---
 read-cache.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/read-cache.c b/read-cache.c
index 3c078afadbc..51845c2e611 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -3126,6 +3126,7 @@ out:
 		free_hashfile(f);
 	strbuf_release(&sb);
 	free(ieot);
+	free(eoie_c);
 	return ret;
 }
 
-- 
gitgitgadget

Re: [PATCH 2/2] read-cache: free hash context in do_write_index()

[Patrick Steinhardt]

On Mon, Sep 30, 2024 at 11:40:24AM +0000, Derrick Stolee via GitGitGadget wrote:
> From: Derrick Stolee <stolee@gmail.com>
> 
> While writing an index, a 'git_hash_ctx' is allocated for hashing the
> file contents. This should be freed as the method exits.
> 
> Signed-off-by: Derrick Stolee <stolee@gmail.com>
> ---
>  read-cache.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/read-cache.c b/read-cache.c
> index 3c078afadbc..51845c2e611 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ -3126,6 +3126,7 @@ out:
>  		free_hashfile(f);
>  	strbuf_release(&sb);
>  	free(ieot);
> +	free(eoie_c);
>  	return ret;
>  }

Yup, this one looks correct. I've sent out an equivalent patch via [1] a
couple hours ago.

Patrick

[1]: https://lore.kernel.org/git/c51f40c5bd0c56967e348363e784222de7884b79.1727687410.git.ps@pks.im/

Re: [PATCH 1/2] read-cache: free threaded memory pool

[Patrick Steinhardt]

On Mon, Sep 30, 2024 at 11:40:23AM +0000, Derrick Stolee via GitGitGadget wrote:
> From: Derrick Stolee <stolee@gmail.com>
> 
> In load_cache_entries_threaded(), each thread is allocated its own

s/allocated/allocating/

> memory pool. This pool needs to be cleaned up while closing the threads
> down, or it will be leaked.
> 
> Signed-off-by: Derrick Stolee <stolee@gmail.com>
> ---
>  read-cache.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/read-cache.c b/read-cache.c
> index 764fdfec465..3c078afadbc 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ -2188,6 +2188,7 @@ static unsigned long load_cache_entries_threaded(struct index_state *istate, con
>  		if (err)
>  			die(_("unable to join load_cache_entries thread: %s"), strerror(err));
>  		mem_pool_combine(istate->ce_mem_pool, p->ce_mem_pool);
> +		free(p->ce_mem_pool);
>  		consumed += p->consumed;
>  	}

Okay. We move over the contents of the pool, but forgot to free the pool
itself. As far as I can see the pool is always allocated and only used
in two functions, both of which assume that it is allocated. So I wonder
why it is allocated in the first place instead of making it a direct
member of `struct load_cache_entries_thread_data`.

Patrick

Re: [PATCH 2/2] read-cache: free hash context in do_write_index()

[Derrick Stolee]

On 9/30/24 8:32 AM, Patrick Steinhardt wrote:
> On Mon, Sep 30, 2024 at 11:40:24AM +0000, Derrick Stolee via GitGitGadget wrote:
>> From: Derrick Stolee <stolee@gmail.com>

>> diff --git a/read-cache.c b/read-cache.c
>> index 3c078afadbc..51845c2e611 100644
>> --- a/read-cache.c
>> +++ b/read-cache.c
>> @@ -3126,6 +3126,7 @@ out:
>>   		free_hashfile(f);
>>   	strbuf_release(&sb);
>>   	free(ieot);
>> +	free(eoie_c);
>>   	return ret;
>>   }
> 
> Yup, this one looks correct. I've sent out an equivalent patch via [1] a
> couple hours ago.
> 
> Patrick
> 
> [1]: https://lore.kernel.org/git/c51f40c5bd0c56967e348363e784222de7884b79.1727687410.git.ps@pks.im/

Sorry for the collision. I had checked when prepping the GGG PR on
Friday but forgot to check again before submitting. Your patch is
better in substance and context.

Thanks,
-Stolee

Re: [PATCH 2/2] read-cache: free hash context in do_write_index()

[Patrick Steinhardt]

On Tue, Oct 01, 2024 at 06:01:06AM -0400, Derrick Stolee wrote:
> On 9/30/24 8:32 AM, Patrick Steinhardt wrote:
> > On Mon, Sep 30, 2024 at 11:40:24AM +0000, Derrick Stolee via GitGitGadget wrote:
> > > From: Derrick Stolee <stolee@gmail.com>
> 
> > > diff --git a/read-cache.c b/read-cache.c
> > > index 3c078afadbc..51845c2e611 100644
> > > --- a/read-cache.c
> > > +++ b/read-cache.c
> > > @@ -3126,6 +3126,7 @@ out:
> > >   		free_hashfile(f);
> > >   	strbuf_release(&sb);
> > >   	free(ieot);
> > > +	free(eoie_c);
> > >   	return ret;
> > >   }
> > 
> > Yup, this one looks correct. I've sent out an equivalent patch via [1] a
> > couple hours ago.
> > 
> > Patrick
> > 
> > [1]: https://lore.kernel.org/git/c51f40c5bd0c56967e348363e784222de7884b79.1727687410.git.ps@pks.im/
> 
> Sorry for the collision. I had checked when prepping the GGG PR on
> Friday but forgot to check again before submitting. Your patch is
> better in substance and context.

Nothing to be sorry about, both series were sent out quite close to one
another. Quite on the contrary, thanks for fixing this leak :)

I don't mind much which of these versions lands in the tree, and the
resulting conflict is trivial to solve anyway.

Patrick

Re: [PATCH 1/2] read-cache: free threaded memory pool

[Derrick Stolee]

On 9/30/24 8:32 AM, Patrick Steinhardt wrote:
> On Mon, Sep 30, 2024 at 11:40:23AM +0000, Derrick Stolee via GitGitGadget wrote:
>> From: Derrick Stolee <stolee@gmail.com>
>>
>> In load_cache_entries_threaded(), each thread is allocated its own
> 
> s/allocated/allocating/

You're right that the wording is awkward but I'm not thrilled with the
suggested alternative.

Perhaps "each thread allocates its own"

>> memory pool. This pool needs to be cleaned up while closing the threads
>> down, or it will be leaked.

> Okay. We move over the contents of the pool, but forgot to free the pool
> itself. As far as I can see the pool is always allocated and only used
> in two functions, both of which assume that it is allocated. So I wonder
> why it is allocated in the first place instead of making it a direct
> member of `struct load_cache_entries_thread_data`.

I took a look at what it would take to replace the pointer with an inline
struct but found complications with situations such as the find_mem_pool()
method. While we could replace some of the logic to recognize the new
type, the existing logic seems to depend on using the NULL pointer as an
indicator that the pool should be lazily initialized.

If we were to pull the struct inline, we would either need another boolean
to indicate initialization or lose lazy initialization.

I'm leaning towards the simpler leak fix over the disruption of that
change.

Thanks,
-Stolee

Re: [PATCH 1/2] read-cache: free threaded memory pool

[Patrick Steinhardt]

On Tue, Oct 01, 2024 at 09:20:01AM -0400, Derrick Stolee wrote:
> On 9/30/24 8:32 AM, Patrick Steinhardt wrote:
> > On Mon, Sep 30, 2024 at 11:40:23AM +0000, Derrick Stolee via GitGitGadget wrote:
> > > From: Derrick Stolee <stolee@gmail.com>
> > > 
> > > In load_cache_entries_threaded(), each thread is allocated its own
> > 
> > s/allocated/allocating/
> 
> You're right that the wording is awkward but I'm not thrilled with the
> suggested alternative.
> 
> Perhaps "each thread allocates its own"

Sure, works for me :)

> > > memory pool. This pool needs to be cleaned up while closing the threads
> > > down, or it will be leaked.
> 
> > Okay. We move over the contents of the pool, but forgot to free the pool
> > itself. As far as I can see the pool is always allocated and only used
> > in two functions, both of which assume that it is allocated. So I wonder
> > why it is allocated in the first place instead of making it a direct
> > member of `struct load_cache_entries_thread_data`.
> 
> I took a look at what it would take to replace the pointer with an inline
> struct but found complications with situations such as the find_mem_pool()
> method. While we could replace some of the logic to recognize the new
> type, the existing logic seems to depend on using the NULL pointer as an
> indicator that the pool should be lazily initialized.
> 
> If we were to pull the struct inline, we would either need another boolean
> to indicate initialization or lose lazy initialization.
> 
> I'm leaning towards the simpler leak fix over the disruption of that
> change.

Fair enough, no complaint from my side. I thought it would've been easy,
but didn't dive deep. So if you say it is harder than I made it out to
be with my shallow understanding I'm going to trust your judgement.
After all, the leak fix is a strict improvement by itself.

Patrick

[PATCH v2] read-cache: free threaded memory pool

[Derrick Stolee via GitGitGadget]

From: Derrick Stolee <stolee@gmail.com>

In load_cache_entries_threaded(), each thread allocates its own memory
pool. This pool needs to be cleaned up while closing the threads down,
or it will be leaked.

This ce_mem_pool pointer could theoretically be converted to an inline
copy of the struct, but the use of a pointer helps with existing lazy-
initialization logic. Adjusting that behavior only to avoid this pointer
would be a much bigger change.

Signed-off-by: Derrick Stolee <stolee@gmail.com>
---
    read-cache: two small leak fixes
    
    This v2 removes the duplicate patch and updates the commit message.
    
    Thanks, -Stolee

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1801%2Fderrickstolee%2Fleaks-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1801/derrickstolee/leaks-v2
Pull-Request: https://github.com/gitgitgadget/git/pull/1801

Range-diff vs v1:

 1:  9a45b15ea4b ! 1:  220a098c93c read-cache: free threaded memory pool
     @@ Metadata
       ## Commit message ##
          read-cache: free threaded memory pool
      
     -    In load_cache_entries_threaded(), each thread is allocated its own
     -    memory pool. This pool needs to be cleaned up while closing the threads
     -    down, or it will be leaked.
     +    In load_cache_entries_threaded(), each thread allocates its own memory
     +    pool. This pool needs to be cleaned up while closing the threads down,
     +    or it will be leaked.
     +
     +    This ce_mem_pool pointer could theoretically be converted to an inline
     +    copy of the struct, but the use of a pointer helps with existing lazy-
     +    initialization logic. Adjusting that behavior only to avoid this pointer
     +    would be a much bigger change.
      
          Signed-off-by: Derrick Stolee <stolee@gmail.com>
      
 2:  b6fe5b3ef7e < -:  ----------- read-cache: free hash context in do_write_index()


 read-cache.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/read-cache.c b/read-cache.c
index 764fdfec465..3c078afadbc 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -2188,6 +2188,7 @@ static unsigned long load_cache_entries_threaded(struct index_state *istate, con
 		if (err)
 			die(_("unable to join load_cache_entries thread: %s"), strerror(err));
 		mem_pool_combine(istate->ce_mem_pool, p->ce_mem_pool);
+		free(p->ce_mem_pool);
 		consumed += p->consumed;
 	}
 

base-commit: 6258f68c3c1092c901337895c864073dcdea9213
-- 
gitgitgadget

Re: [PATCH v2] read-cache: free threaded memory pool

[Patrick Steinhardt]

On Tue, Oct 01, 2024 at 05:37:44PM +0000, Derrick Stolee via GitGitGadget wrote:
> From: Derrick Stolee <stolee@gmail.com>
> 
> In load_cache_entries_threaded(), each thread allocates its own memory
> pool. This pool needs to be cleaned up while closing the threads down,
> or it will be leaked.
> 
> This ce_mem_pool pointer could theoretically be converted to an inline
> copy of the struct, but the use of a pointer helps with existing lazy-
> initialization logic. Adjusting that behavior only to avoid this pointer
> would be a much bigger change.

Thanks, this looks good to me.

Patrick