* [PATCH RFC] btrfs: make btrfs module init/exit match their sequence
@ 2022-09-19 6:36 Qu Wenruo
2022-09-19 20:13 ` David Sterba
0 siblings, 1 reply; 3+ messages in thread
From: Qu Wenruo @ 2022-09-19 6:36 UTC (permalink / raw)
To: linux-btrfs
[BACKGROUND]
In theory init_btrfs_fs() and exit_btrfs_fs() should match their
sequence, thus normally they should look like this:
init_btrfs_fs() | exit_btrfs_fs()
----------------------+------------------------
init_A(); |
init_B(); |
init_C(); |
| exit_C();
| exit_B();
| exit_A();
So is for the error path of init_btrfs_fs().
But it's not the case, some exit functions don't match their init
functions sequence in init_btrfs_fs().
Furthermore in init_btrfs_fs(), we need to have a new error tag for each
new init function we added.
This is not really expandable, especially recently we may add several
new functions to init_btrfs_fs().
[ENHANCEMENT]
The patch will introduce the following things to enhance the situation:
- struct init_sequence
Just a wrapper of init and exit function pointers.
The init function must use int type as return value, thus some init
functions need to be updated to return 0.
The exit function can be NULL, as there are some init sequence just
outputting a message.
- struct mod_init_seq[] array
This is a const array, recording all the initialization we need to do
in init_btrfs_fs(), and the order follows the old init_btrfs_fs().
Only one modification in the order, now we call btrfs_print_mod_info()
after sanity checks.
As it makes no sense to print the mod into, and fail the sanity tests.
- bool mod_init_result[] array
This is a bool array, recording if we have initialized one entry in
mod_init_seq[].
The reason to split mod_init_seq[] and mod_init_result[] is to avoid
section mismatch in reference.
All init function are in .init.text, but if mod_init_seq[] records
the @initialized member it can no longer be const, thus will be put
into .data section, and cause modpost warning.
For init_btrfs_fs() we just call all init functions in their order in
mod_init_seq[] array, and after each call, setting corresponding
mod_init_result[] to true.
For exit_btrfs_fs() and error handling path of init_btrfs_fs(), we just
iterate mod_init_seq[] in reverse order, and skip all uninitialized
entry.
With this patch, init_btrfs_fs()/exit_btrfs_fs() will be much easier to
expand and will always follow the strict order.
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
Reason for RFC:
Although the patch is tested with multiple load/unload and fstests runs,
this should cause extra memory usage, 272 bytes for the single use
mod_init_seq[] array and at least 17 bytes for mod_init_result[].
And it also introduced some duplicated code, as we can not call
exit_btrfs_fs() inside init_btrfs_fs(), or we will trigger modpost
warning for the section type mismatch in the reference.
Another solution is, to make all exit functions to handle the cleanup
automatically.
This is feasible for most cachep related init/exit, just some extra
"if (cachep) {" checks.
But some other ones may need extra work.
Furthermore such smart exit function can not address the sequence
problem, only making the error handling patch a little cleaner.
Thus currently I follow the array solution for this.
If this method is fine, maybe I can follow the same way for open_ctree().
---
fs/btrfs/compression.c | 3 +-
fs/btrfs/compression.h | 2 +-
fs/btrfs/props.c | 3 +-
fs/btrfs/props.h | 2 +-
fs/btrfs/super.c | 211 +++++++++++++++++++++--------------------
5 files changed, 112 insertions(+), 109 deletions(-)
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 54caa00a2245..8d3e3218fe37 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1232,12 +1232,13 @@ int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
return ret;
}
-void __init btrfs_init_compress(void)
+int __init btrfs_init_compress(void)
{
btrfs_init_workspace_manager(BTRFS_COMPRESS_NONE);
btrfs_init_workspace_manager(BTRFS_COMPRESS_ZLIB);
btrfs_init_workspace_manager(BTRFS_COMPRESS_LZO);
zstd_init_workspace_manager();
+ return 0;
}
void __cold btrfs_exit_compress(void)
diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index 1aa02903de69..9da2343eeff5 100644
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -77,7 +77,7 @@ static inline unsigned int btrfs_compress_level(unsigned int type_level)
return ((type_level & 0xF0) >> 4);
}
-void __init btrfs_init_compress(void);
+int __init btrfs_init_compress(void);
void __cold btrfs_exit_compress(void);
int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
index 055a631276ce..abee92eb1ed6 100644
--- a/fs/btrfs/props.c
+++ b/fs/btrfs/props.c
@@ -453,7 +453,7 @@ int btrfs_inode_inherit_props(struct btrfs_trans_handle *trans,
return 0;
}
-void __init btrfs_props_init(void)
+int __init btrfs_props_init(void)
{
int i;
@@ -463,5 +463,6 @@ void __init btrfs_props_init(void)
hash_add(prop_handlers_ht, &p->node, h);
}
+ return 0;
}
diff --git a/fs/btrfs/props.h b/fs/btrfs/props.h
index ca9dd3df129b..6e283196e38a 100644
--- a/fs/btrfs/props.h
+++ b/fs/btrfs/props.h
@@ -8,7 +8,7 @@
#include "ctree.h"
-void __init btrfs_props_init(void);
+int __init btrfs_props_init(void);
int btrfs_set_prop(struct btrfs_trans_handle *trans, struct inode *inode,
const char *name, const char *value, size_t value_len,
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index be7df8d1d5b8..fb30ca46c65c 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2691,7 +2691,7 @@ static __cold void btrfs_interface_exit(void)
misc_deregister(&btrfs_misc);
}
-static void __init btrfs_print_mod_info(void)
+static int __init btrfs_print_mod_info(void)
{
static const char options[] = ""
#ifdef CONFIG_BTRFS_DEBUG
@@ -2718,122 +2718,123 @@ static void __init btrfs_print_mod_info(void)
#endif
;
pr_info("Btrfs loaded, crc32c=%s%s\n", crc32c_impl(), options);
+ return 0;
}
-static int __init init_btrfs_fs(void)
+static int register_btrfs(void)
{
- int err;
-
- btrfs_props_init();
-
- err = btrfs_init_sysfs();
- if (err)
- return err;
-
- btrfs_init_compress();
-
- err = btrfs_init_cachep();
- if (err)
- goto free_compress;
-
- err = extent_state_init_cachep();
- if (err)
- goto free_cachep;
-
- err = extent_buffer_init_cachep();
- if (err)
- goto free_extent_cachep;
-
- err = btrfs_bioset_init();
- if (err)
- goto free_eb_cachep;
-
- err = extent_map_init();
- if (err)
- goto free_bioset;
-
- err = ordered_data_init();
- if (err)
- goto free_extent_map;
-
- err = btrfs_delayed_inode_init();
- if (err)
- goto free_ordered_data;
-
- err = btrfs_auto_defrag_init();
- if (err)
- goto free_delayed_inode;
-
- err = btrfs_delayed_ref_init();
- if (err)
- goto free_auto_defrag;
+ return register_filesystem(&btrfs_fs_type);
+}
+static void unregister_btrfs(void)
+{
+ unregister_filesystem(&btrfs_fs_type);
+}
- err = btrfs_prelim_ref_init();
- if (err)
- goto free_delayed_ref;
+/* Helper structure for long init/exit functions. */
+struct init_sequence {
+ int (*init_func)(void);
+ void (*exit_func)(void);
+};
- err = btrfs_interface_init();
- if (err)
- goto free_prelim_ref;
+const struct init_sequence mod_init_seq[] = {
+ {
+ .init_func = btrfs_props_init,
+ .exit_func = NULL,
+ }, {
+ .init_func = btrfs_init_sysfs,
+ .exit_func = btrfs_exit_sysfs,
+ }, {
+ .init_func = btrfs_init_compress,
+ .exit_func = btrfs_exit_compress,
+ }, {
+ .init_func = btrfs_init_cachep,
+ .exit_func = btrfs_destroy_cachep,
+ }, {
+ .init_func = extent_state_init_cachep,
+ .exit_func = extent_state_free_cachep,
+ }, {
+ .init_func = extent_buffer_init_cachep,
+ .exit_func = extent_buffer_free_cachep,
+ }, {
+ .init_func = btrfs_bioset_init,
+ .exit_func = btrfs_bioset_exit,
+ }, {
+ .init_func = extent_map_init,
+ .exit_func = extent_map_exit,
+ }, {
+ .init_func = ordered_data_init,
+ .exit_func = ordered_data_exit,
+ }, {
+ .init_func = btrfs_delayed_inode_init,
+ .exit_func = btrfs_delayed_inode_exit,
+ }, {
+ .init_func = btrfs_auto_defrag_init,
+ .exit_func = btrfs_auto_defrag_exit,
+ }, {
+ .init_func = btrfs_delayed_ref_init,
+ .exit_func = btrfs_delayed_ref_exit,
+ }, {
+ .init_func = btrfs_prelim_ref_init,
+ .exit_func = btrfs_prelim_ref_exit,
+ }, {
+ .init_func = btrfs_interface_init,
+ .exit_func = btrfs_interface_exit,
+ }, {
+ .init_func = btrfs_run_sanity_tests,
+ .exit_func = NULL,
+ }, {
+ .init_func = btrfs_print_mod_info,
+ .exit_func = NULL,
+ }, {
+ .init_func = register_btrfs,
+ .exit_func = unregister_btrfs,
+ }
+};
- btrfs_print_mod_info();
+static bool mod_init_result[ARRAY_SIZE(mod_init_seq)];
- err = btrfs_run_sanity_tests();
- if (err)
- goto unregister_ioctl;
+static void __exit exit_btrfs_fs(void)
+{
+ int i;
- err = register_filesystem(&btrfs_fs_type);
- if (err)
- goto unregister_ioctl;
+ for (i = ARRAY_SIZE(mod_init_seq) - 1; i >= 0; i--) {
+ if (!mod_init_result[i])
+ continue;
+ if (mod_init_seq[i].exit_func)
+ mod_init_seq[i].exit_func();
+ mod_init_result[i] = false;
+ }
+}
+static int __init init_btrfs_fs(void)
+{
+ int ret;
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(mod_init_seq); i++) {
+ ASSERT(!mod_init_result[i]);
+ ret = mod_init_seq[i].init_func();
+ if (ret < 0)
+ goto error;
+ mod_init_result[i] = true;
+ }
return 0;
-unregister_ioctl:
- btrfs_interface_exit();
-free_prelim_ref:
- btrfs_prelim_ref_exit();
-free_delayed_ref:
- btrfs_delayed_ref_exit();
-free_auto_defrag:
- btrfs_auto_defrag_exit();
-free_delayed_inode:
- btrfs_delayed_inode_exit();
-free_ordered_data:
- ordered_data_exit();
-free_extent_map:
- extent_map_exit();
-free_bioset:
- btrfs_bioset_exit();
-free_eb_cachep:
- extent_buffer_free_cachep();
-free_extent_cachep:
- extent_state_free_cachep();
-free_cachep:
- btrfs_destroy_cachep();
-free_compress:
- btrfs_exit_compress();
- btrfs_exit_sysfs();
-
- return err;
-}
+error:
+ /*
+ * If we call exit_btrfs_fs() it would cause section mismatch.
+ * As init_btrfs_fs() belongs to .init.text, while exit_btrfs_fs()
+ * belongs to .exit.text.
+ */
+ for (i = ARRAY_SIZE(mod_init_seq) - 1; i >= 0; i--) {
+ if (!mod_init_result[i])
+ continue;
+ if (mod_init_seq[i].exit_func)
+ mod_init_seq[i].exit_func();
+ mod_init_result[i] = false;
+ }
+ return ret;
-static void __exit exit_btrfs_fs(void)
-{
- btrfs_destroy_cachep();
- btrfs_delayed_ref_exit();
- btrfs_auto_defrag_exit();
- btrfs_delayed_inode_exit();
- btrfs_prelim_ref_exit();
- ordered_data_exit();
- extent_map_exit();
- btrfs_bioset_exit();
- extent_state_free_cachep();
- extent_buffer_free_cachep();
- btrfs_interface_exit();
- unregister_filesystem(&btrfs_fs_type);
- btrfs_exit_sysfs();
- btrfs_cleanup_fs_uuids();
- btrfs_exit_compress();
}
late_initcall(init_btrfs_fs);
--
2.37.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH RFC] btrfs: make btrfs module init/exit match their sequence
2022-09-19 6:36 [PATCH RFC] btrfs: make btrfs module init/exit match their sequence Qu Wenruo
@ 2022-09-19 20:13 ` David Sterba
2022-09-19 23:00 ` Qu Wenruo
0 siblings, 1 reply; 3+ messages in thread
From: David Sterba @ 2022-09-19 20:13 UTC (permalink / raw)
To: Qu Wenruo; +Cc: linux-btrfs
On Mon, Sep 19, 2022 at 02:36:44PM +0800, Qu Wenruo wrote:
> [BACKGROUND]
> In theory init_btrfs_fs() and exit_btrfs_fs() should match their
> sequence, thus normally they should look like this:
>
> init_btrfs_fs() | exit_btrfs_fs()
> ----------------------+------------------------
> init_A(); |
> init_B(); |
> init_C(); |
> | exit_C();
> | exit_B();
> | exit_A();
>
> So is for the error path of init_btrfs_fs().
>
> But it's not the case, some exit functions don't match their init
> functions sequence in init_btrfs_fs().
>
> Furthermore in init_btrfs_fs(), we need to have a new error tag for each
> new init function we added.
> This is not really expandable, especially recently we may add several
> new functions to init_btrfs_fs().
>
> [ENHANCEMENT]
> The patch will introduce the following things to enhance the situation:
>
> - struct init_sequence
> Just a wrapper of init and exit function pointers.
>
> The init function must use int type as return value, thus some init
> functions need to be updated to return 0.
>
> The exit function can be NULL, as there are some init sequence just
> outputting a message.
>
> - struct mod_init_seq[] array
> This is a const array, recording all the initialization we need to do
> in init_btrfs_fs(), and the order follows the old init_btrfs_fs().
>
> Only one modification in the order, now we call btrfs_print_mod_info()
> after sanity checks.
> As it makes no sense to print the mod into, and fail the sanity tests.
>
> - bool mod_init_result[] array
> This is a bool array, recording if we have initialized one entry in
> mod_init_seq[].
>
> The reason to split mod_init_seq[] and mod_init_result[] is to avoid
> section mismatch in reference.
>
> All init function are in .init.text, but if mod_init_seq[] records
> the @initialized member it can no longer be const, thus will be put
> into .data section, and cause modpost warning.
>
> For init_btrfs_fs() we just call all init functions in their order in
> mod_init_seq[] array, and after each call, setting corresponding
> mod_init_result[] to true.
>
> For exit_btrfs_fs() and error handling path of init_btrfs_fs(), we just
> iterate mod_init_seq[] in reverse order, and skip all uninitialized
> entry.
>
> With this patch, init_btrfs_fs()/exit_btrfs_fs() will be much easier to
> expand and will always follow the strict order.
>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
> Reason for RFC:
>
> Although the patch is tested with multiple load/unload and fstests runs,
> this should cause extra memory usage, 272 bytes for the single use
> mod_init_seq[] array and at least 17 bytes for mod_init_result[].
I think the bytes will move from code to the data section, so I would
not consider it a big problem.
> And it also introduced some duplicated code, as we can not call
> exit_btrfs_fs() inside init_btrfs_fs(), or we will trigger modpost
> warning for the section type mismatch in the reference.
>
> Another solution is, to make all exit functions to handle the cleanup
> automatically.
>
> This is feasible for most cachep related init/exit, just some extra
> "if (cachep) {" checks.
> But some other ones may need extra work.
> Furthermore such smart exit function can not address the sequence
> problem, only making the error handling patch a little cleaner.
>
> Thus currently I follow the array solution for this.
>
> If this method is fine, maybe I can follow the same way for open_ctree().
I like it, the order of the functions is clear and makes it easy to
extend in one place. As now implemented I don't see anything oubvious
that would need an improvement so the suggested optimizations we can
consider separately.
> ---
> fs/btrfs/compression.c | 3 +-
> fs/btrfs/compression.h | 2 +-
> fs/btrfs/props.c | 3 +-
> fs/btrfs/props.h | 2 +-
> fs/btrfs/super.c | 211 +++++++++++++++++++++--------------------
> 5 files changed, 112 insertions(+), 109 deletions(-)
>
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index 54caa00a2245..8d3e3218fe37 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -1232,12 +1232,13 @@ int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
> return ret;
> }
>
> -void __init btrfs_init_compress(void)
> +int __init btrfs_init_compress(void)
> {
> btrfs_init_workspace_manager(BTRFS_COMPRESS_NONE);
> btrfs_init_workspace_manager(BTRFS_COMPRESS_ZLIB);
> btrfs_init_workspace_manager(BTRFS_COMPRESS_LZO);
> zstd_init_workspace_manager();
> + return 0;
> }
>
> void __cold btrfs_exit_compress(void)
> diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
> index 1aa02903de69..9da2343eeff5 100644
> --- a/fs/btrfs/compression.h
> +++ b/fs/btrfs/compression.h
> @@ -77,7 +77,7 @@ static inline unsigned int btrfs_compress_level(unsigned int type_level)
> return ((type_level & 0xF0) >> 4);
> }
>
> -void __init btrfs_init_compress(void);
> +int __init btrfs_init_compress(void);
> void __cold btrfs_exit_compress(void);
>
> int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
> diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
> index 055a631276ce..abee92eb1ed6 100644
> --- a/fs/btrfs/props.c
> +++ b/fs/btrfs/props.c
> @@ -453,7 +453,7 @@ int btrfs_inode_inherit_props(struct btrfs_trans_handle *trans,
> return 0;
> }
>
> -void __init btrfs_props_init(void)
> +int __init btrfs_props_init(void)
> {
> int i;
>
> @@ -463,5 +463,6 @@ void __init btrfs_props_init(void)
>
> hash_add(prop_handlers_ht, &p->node, h);
> }
> + return 0;
> }
>
> diff --git a/fs/btrfs/props.h b/fs/btrfs/props.h
> index ca9dd3df129b..6e283196e38a 100644
> --- a/fs/btrfs/props.h
> +++ b/fs/btrfs/props.h
> @@ -8,7 +8,7 @@
>
> #include "ctree.h"
>
> -void __init btrfs_props_init(void);
> +int __init btrfs_props_init(void);
>
> int btrfs_set_prop(struct btrfs_trans_handle *trans, struct inode *inode,
> const char *name, const char *value, size_t value_len,
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index be7df8d1d5b8..fb30ca46c65c 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -2691,7 +2691,7 @@ static __cold void btrfs_interface_exit(void)
> misc_deregister(&btrfs_misc);
> }
>
> -static void __init btrfs_print_mod_info(void)
> +static int __init btrfs_print_mod_info(void)
> {
> static const char options[] = ""
> #ifdef CONFIG_BTRFS_DEBUG
> @@ -2718,122 +2718,123 @@ static void __init btrfs_print_mod_info(void)
> #endif
> ;
> pr_info("Btrfs loaded, crc32c=%s%s\n", crc32c_impl(), options);
> + return 0;
> }
>
> -static int __init init_btrfs_fs(void)
> +static int register_btrfs(void)
> {
> - int err;
> -
> - btrfs_props_init();
> -
> - err = btrfs_init_sysfs();
> - if (err)
> - return err;
> -
> - btrfs_init_compress();
> -
> - err = btrfs_init_cachep();
> - if (err)
> - goto free_compress;
> -
> - err = extent_state_init_cachep();
> - if (err)
> - goto free_cachep;
> -
> - err = extent_buffer_init_cachep();
> - if (err)
> - goto free_extent_cachep;
> -
> - err = btrfs_bioset_init();
> - if (err)
> - goto free_eb_cachep;
> -
> - err = extent_map_init();
> - if (err)
> - goto free_bioset;
> -
> - err = ordered_data_init();
> - if (err)
> - goto free_extent_map;
> -
> - err = btrfs_delayed_inode_init();
> - if (err)
> - goto free_ordered_data;
> -
> - err = btrfs_auto_defrag_init();
> - if (err)
> - goto free_delayed_inode;
> -
> - err = btrfs_delayed_ref_init();
> - if (err)
> - goto free_auto_defrag;
> + return register_filesystem(&btrfs_fs_type);
> +}
> +static void unregister_btrfs(void)
> +{
> + unregister_filesystem(&btrfs_fs_type);
> +}
>
> - err = btrfs_prelim_ref_init();
> - if (err)
> - goto free_delayed_ref;
> +/* Helper structure for long init/exit functions. */
> +struct init_sequence {
> + int (*init_func)(void);
> + void (*exit_func)(void);
> +};
>
> - err = btrfs_interface_init();
> - if (err)
> - goto free_prelim_ref;
> +const struct init_sequence mod_init_seq[] = {
Can this be static? Also it could be marked as the __initdata section or
it's called something like that, like the functions. It can freed some
resources when the module is built-in.
> + {
> + .init_func = btrfs_props_init,
> + .exit_func = NULL,
We can put the defintion in some macro, that would define both callbacks
if they follow same naming eg. with _init _exit suffix bit it slightly
obscures the function use. The full list as you've done it is fine for
first implementation and it could stay as is.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH RFC] btrfs: make btrfs module init/exit match their sequence
2022-09-19 20:13 ` David Sterba
@ 2022-09-19 23:00 ` Qu Wenruo
0 siblings, 0 replies; 3+ messages in thread
From: Qu Wenruo @ 2022-09-19 23:00 UTC (permalink / raw)
To: dsterba, Qu Wenruo; +Cc: linux-btrfs
On 2022/9/20 04:13, David Sterba wrote:
> On Mon, Sep 19, 2022 at 02:36:44PM +0800, Qu Wenruo wrote:
>> [BACKGROUND]
>> In theory init_btrfs_fs() and exit_btrfs_fs() should match their
>> sequence, thus normally they should look like this:
>>
>> init_btrfs_fs() | exit_btrfs_fs()
>> ----------------------+------------------------
>> init_A(); |
>> init_B(); |
>> init_C(); |
>> | exit_C();
>> | exit_B();
>> | exit_A();
>>
>> So is for the error path of init_btrfs_fs().
>>
>> But it's not the case, some exit functions don't match their init
>> functions sequence in init_btrfs_fs().
>>
>> Furthermore in init_btrfs_fs(), we need to have a new error tag for each
>> new init function we added.
>> This is not really expandable, especially recently we may add several
>> new functions to init_btrfs_fs().
>>
>> [ENHANCEMENT]
>> The patch will introduce the following things to enhance the situation:
>>
>> - struct init_sequence
>> Just a wrapper of init and exit function pointers.
>>
>> The init function must use int type as return value, thus some init
>> functions need to be updated to return 0.
>>
>> The exit function can be NULL, as there are some init sequence just
>> outputting a message.
>>
>> - struct mod_init_seq[] array
>> This is a const array, recording all the initialization we need to do
>> in init_btrfs_fs(), and the order follows the old init_btrfs_fs().
>>
>> Only one modification in the order, now we call btrfs_print_mod_info()
>> after sanity checks.
>> As it makes no sense to print the mod into, and fail the sanity tests.
>>
>> - bool mod_init_result[] array
>> This is a bool array, recording if we have initialized one entry in
>> mod_init_seq[].
>>
>> The reason to split mod_init_seq[] and mod_init_result[] is to avoid
>> section mismatch in reference.
>>
>> All init function are in .init.text, but if mod_init_seq[] records
>> the @initialized member it can no longer be const, thus will be put
>> into .data section, and cause modpost warning.
>>
>> For init_btrfs_fs() we just call all init functions in their order in
>> mod_init_seq[] array, and after each call, setting corresponding
>> mod_init_result[] to true.
>>
>> For exit_btrfs_fs() and error handling path of init_btrfs_fs(), we just
>> iterate mod_init_seq[] in reverse order, and skip all uninitialized
>> entry.
>>
>> With this patch, init_btrfs_fs()/exit_btrfs_fs() will be much easier to
>> expand and will always follow the strict order.
>>
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
>> ---
>> Reason for RFC:
>>
>> Although the patch is tested with multiple load/unload and fstests runs,
>> this should cause extra memory usage, 272 bytes for the single use
>> mod_init_seq[] array and at least 17 bytes for mod_init_result[].
>
> I think the bytes will move from code to the data section, so I would
> not consider it a big problem.
>
>> And it also introduced some duplicated code, as we can not call
>> exit_btrfs_fs() inside init_btrfs_fs(), or we will trigger modpost
>> warning for the section type mismatch in the reference.
>>
>> Another solution is, to make all exit functions to handle the cleanup
>> automatically.
>>
>> This is feasible for most cachep related init/exit, just some extra
>> "if (cachep) {" checks.
>> But some other ones may need extra work.
>> Furthermore such smart exit function can not address the sequence
>> problem, only making the error handling patch a little cleaner.
>>
>> Thus currently I follow the array solution for this.
>>
>> If this method is fine, maybe I can follow the same way for open_ctree().
>
> I like it, the order of the functions is clear and makes it easy to
> extend in one place. As now implemented I don't see anything oubvious
> that would need an improvement so the suggested optimizations we can
> consider separately.
>
>> ---
>> fs/btrfs/compression.c | 3 +-
>> fs/btrfs/compression.h | 2 +-
>> fs/btrfs/props.c | 3 +-
>> fs/btrfs/props.h | 2 +-
>> fs/btrfs/super.c | 211 +++++++++++++++++++++--------------------
>> 5 files changed, 112 insertions(+), 109 deletions(-)
>>
>> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
>> index 54caa00a2245..8d3e3218fe37 100644
>> --- a/fs/btrfs/compression.c
>> +++ b/fs/btrfs/compression.c
>> @@ -1232,12 +1232,13 @@ int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
>> return ret;
>> }
>>
>> -void __init btrfs_init_compress(void)
>> +int __init btrfs_init_compress(void)
>> {
>> btrfs_init_workspace_manager(BTRFS_COMPRESS_NONE);
>> btrfs_init_workspace_manager(BTRFS_COMPRESS_ZLIB);
>> btrfs_init_workspace_manager(BTRFS_COMPRESS_LZO);
>> zstd_init_workspace_manager();
>> + return 0;
>> }
>>
>> void __cold btrfs_exit_compress(void)
>> diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
>> index 1aa02903de69..9da2343eeff5 100644
>> --- a/fs/btrfs/compression.h
>> +++ b/fs/btrfs/compression.h
>> @@ -77,7 +77,7 @@ static inline unsigned int btrfs_compress_level(unsigned int type_level)
>> return ((type_level & 0xF0) >> 4);
>> }
>>
>> -void __init btrfs_init_compress(void);
>> +int __init btrfs_init_compress(void);
>> void __cold btrfs_exit_compress(void);
>>
>> int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
>> diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
>> index 055a631276ce..abee92eb1ed6 100644
>> --- a/fs/btrfs/props.c
>> +++ b/fs/btrfs/props.c
>> @@ -453,7 +453,7 @@ int btrfs_inode_inherit_props(struct btrfs_trans_handle *trans,
>> return 0;
>> }
>>
>> -void __init btrfs_props_init(void)
>> +int __init btrfs_props_init(void)
>> {
>> int i;
>>
>> @@ -463,5 +463,6 @@ void __init btrfs_props_init(void)
>>
>> hash_add(prop_handlers_ht, &p->node, h);
>> }
>> + return 0;
>> }
>>
>> diff --git a/fs/btrfs/props.h b/fs/btrfs/props.h
>> index ca9dd3df129b..6e283196e38a 100644
>> --- a/fs/btrfs/props.h
>> +++ b/fs/btrfs/props.h
>> @@ -8,7 +8,7 @@
>>
>> #include "ctree.h"
>>
>> -void __init btrfs_props_init(void);
>> +int __init btrfs_props_init(void);
>>
>> int btrfs_set_prop(struct btrfs_trans_handle *trans, struct inode *inode,
>> const char *name, const char *value, size_t value_len,
>> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
>> index be7df8d1d5b8..fb30ca46c65c 100644
>> --- a/fs/btrfs/super.c
>> +++ b/fs/btrfs/super.c
>> @@ -2691,7 +2691,7 @@ static __cold void btrfs_interface_exit(void)
>> misc_deregister(&btrfs_misc);
>> }
>>
>> -static void __init btrfs_print_mod_info(void)
>> +static int __init btrfs_print_mod_info(void)
>> {
>> static const char options[] = ""
>> #ifdef CONFIG_BTRFS_DEBUG
>> @@ -2718,122 +2718,123 @@ static void __init btrfs_print_mod_info(void)
>> #endif
>> ;
>> pr_info("Btrfs loaded, crc32c=%s%s\n", crc32c_impl(), options);
>> + return 0;
>> }
>>
>> -static int __init init_btrfs_fs(void)
>> +static int register_btrfs(void)
>> {
>> - int err;
>> -
>> - btrfs_props_init();
>> -
>> - err = btrfs_init_sysfs();
>> - if (err)
>> - return err;
>> -
>> - btrfs_init_compress();
>> -
>> - err = btrfs_init_cachep();
>> - if (err)
>> - goto free_compress;
>> -
>> - err = extent_state_init_cachep();
>> - if (err)
>> - goto free_cachep;
>> -
>> - err = extent_buffer_init_cachep();
>> - if (err)
>> - goto free_extent_cachep;
>> -
>> - err = btrfs_bioset_init();
>> - if (err)
>> - goto free_eb_cachep;
>> -
>> - err = extent_map_init();
>> - if (err)
>> - goto free_bioset;
>> -
>> - err = ordered_data_init();
>> - if (err)
>> - goto free_extent_map;
>> -
>> - err = btrfs_delayed_inode_init();
>> - if (err)
>> - goto free_ordered_data;
>> -
>> - err = btrfs_auto_defrag_init();
>> - if (err)
>> - goto free_delayed_inode;
>> -
>> - err = btrfs_delayed_ref_init();
>> - if (err)
>> - goto free_auto_defrag;
>> + return register_filesystem(&btrfs_fs_type);
>> +}
>> +static void unregister_btrfs(void)
>> +{
>> + unregister_filesystem(&btrfs_fs_type);
>> +}
>>
>> - err = btrfs_prelim_ref_init();
>> - if (err)
>> - goto free_delayed_ref;
>> +/* Helper structure for long init/exit functions. */
>> +struct init_sequence {
>> + int (*init_func)(void);
>> + void (*exit_func)(void);
>> +};
>>
>> - err = btrfs_interface_init();
>> - if (err)
>> - goto free_prelim_ref;
>> +const struct init_sequence mod_init_seq[] = {
>
> Can this be static? Also it could be marked as the __initdata section or
> it's called something like that, like the functions. It can freed some
> resources when the module is built-in.
Yep, for const structure array it can definitely be static without
modpost wanring.
>
>> + {
>> + .init_func = btrfs_props_init,
>> + .exit_func = NULL,
>
> We can put the defintion in some macro, that would define both callbacks
> if they follow same naming eg. with _init _exit suffix bit it slightly
> obscures the function use. The full list as you've done it is fine for
> first implementation and it could stay as is.
That is possible especially most of the init/exit functions are already
doing the init/exit naming, although we need some renaming to put
init/exit as suffix.
That can be a separate patch for further improvement.
Thanks,
Qu
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-09-19 23:00 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-09-19 6:36 [PATCH RFC] btrfs: make btrfs module init/exit match their sequence Qu Wenruo
2022-09-19 20:13 ` David Sterba
2022-09-19 23:00 ` Qu Wenruo
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.