Re: [PATCH] blk-cgroup: explicitly init the early_init field
On 04/22/2014 08:18 AM, Jianyu Zhan wrote: > On Tue, Apr 22, 2014 at 10:16 PM, Jens Axboe wrote: >> The rest of the members will be zero-filled by default, so your patch should >> not change anything. > > Hi, Jens > > I'm sorry I should have made this more clear. > > Sure, for this global variable struct, if not initailized, its all > fields will be initialized > to 0 or null(depending on its type). The point here is no to deprive > the rights of compiler/linker of doing this initialization, it is mainly for > documentation reason. Actually this field's value would affect how ->css_alloc > should implemented. > > Concretely, if early_init is nonzero, then ->css_alloc *must not* call > kzalloc, > because in cgroup implementation, ->css_alloc will be called earlier before > mm_init(). > > I don't think that the value of one field(early_init) has a so subtle > restrition on the another field(css_alloc) is a good thing, but since > it is there, docment it should be needed. Then just add the comment instead. The fact the members following the last " = something," are zeroed is a common theme in the kernel, if you just add a patch that blindly (and unnecessarily) zeroes one other member, somebody else will likely find that odd and remove it again. To be honest, I don't see much of a need to do anything here, really. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] blk-cgroup: explicitly init the early_init field
On Tue, Apr 22, 2014 at 10:16 PM, Jens Axboe wrote: > The rest of the members will be zero-filled by default, so your patch should > not change anything. Hi, Jens I'm sorry I should have made this more clear. Sure, for this global variable struct, if not initailized, its all fields will be initialized to 0 or null(depending on its type). The point here is no to deprive the rights of compiler/linker of doing this initialization, it is mainly for documentation reason. Actually this field's value would affect how ->css_alloc should implemented. Concretely, if early_init is nonzero, then ->css_alloc *must not* call kzalloc, because in cgroup implementation, ->css_alloc will be called earlier before mm_init(). I don't think that the value of one field(early_init) has a so subtle restrition on the another field(css_alloc) is a good thing, but since it is there, docment it should be needed. Thanks, Jianyu Zhan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] blk-cgroup: explicitly init the early_init field
On 2014-04-21 23:26, Jianyu Zhan wrote: For a cgroup subsystem who should init early, then it should carefully take care of the implementation of css_alloc, because it will be called before mm_init() setup the world. Luckily we don't, and we better explicitly assign the early_init field to 0, for document reason. The rest of the members will be zero-filled by default, so your patch should not change anything. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] blk-cgroup: explicitly init the early_init field
On 2014-04-21 23:26, Jianyu Zhan wrote: For a cgroup subsystem who should init early, then it should carefully take care of the implementation of css_alloc, because it will be called before mm_init() setup the world. Luckily we don't, and we better explicitly assign the early_init field to 0, for document reason. The rest of the members will be zero-filled by default, so your patch should not change anything. -- Jens Axboe -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] blk-cgroup: explicitly init the early_init field
On Tue, Apr 22, 2014 at 10:16 PM, Jens Axboe ax...@kernel.dk wrote: The rest of the members will be zero-filled by default, so your patch should not change anything. Hi, Jens I'm sorry I should have made this more clear. Sure, for this global variable struct, if not initailized, its all fields will be initialized to 0 or null(depending on its type). The point here is no to deprive the rights of compiler/linker of doing this initialization, it is mainly for documentation reason. Actually this field's value would affect how -css_alloc should implemented. Concretely, if early_init is nonzero, then -css_alloc *must not* call kzalloc, because in cgroup implementation, -css_alloc will be called earlier before mm_init(). I don't think that the value of one field(early_init) has a so subtle restrition on the another field(css_alloc) is a good thing, but since it is there, docment it should be needed. Thanks, Jianyu Zhan -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] blk-cgroup: explicitly init the early_init field
On 04/22/2014 08:18 AM, Jianyu Zhan wrote: On Tue, Apr 22, 2014 at 10:16 PM, Jens Axboe ax...@kernel.dk wrote: The rest of the members will be zero-filled by default, so your patch should not change anything. Hi, Jens I'm sorry I should have made this more clear. Sure, for this global variable struct, if not initailized, its all fields will be initialized to 0 or null(depending on its type). The point here is no to deprive the rights of compiler/linker of doing this initialization, it is mainly for documentation reason. Actually this field's value would affect how -css_alloc should implemented. Concretely, if early_init is nonzero, then -css_alloc *must not* call kzalloc, because in cgroup implementation, -css_alloc will be called earlier before mm_init(). I don't think that the value of one field(early_init) has a so subtle restrition on the another field(css_alloc) is a good thing, but since it is there, docment it should be needed. Then just add the comment instead. The fact the members following the last = something, are zeroed is a common theme in the kernel, if you just add a patch that blindly (and unnecessarily) zeroes one other member, somebody else will likely find that odd and remove it again. To be honest, I don't see much of a need to do anything here, really. -- Jens Axboe -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH] blk-cgroup: explicitly init the early_init field
For a cgroup subsystem who should init early, then it should carefully
take care of the implementation of css_alloc, because it will be called
before mm_init() setup the world.
Luckily we don't, and we better explicitly assign the early_init field
to 0, for document reason.
Signed-off-by: Jianyu Zhan
---
block/blk-cgroup.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index e4a4145..941bbc8 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -912,6 +912,7 @@ struct cgroup_subsys blkio_cgrp_subsys = {
.css_free = blkcg_css_free,
.can_attach = blkcg_can_attach,
.base_cftypes = blkcg_files,
+ .early_init = 0,
};
EXPORT_SYMBOL_GPL(blkio_cgrp_subsys);
--
2.0.0-rc0
--
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the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH] blk-cgroup: explicitly init the early_init field
For a cgroup subsystem who should init early, then it should carefully
take care of the implementation of css_alloc, because it will be called
before mm_init() setup the world.
Luckily we don't, and we better explicitly assign the early_init field
to 0, for document reason.
Signed-off-by: Jianyu Zhan nasa4...@gmail.com
---
block/blk-cgroup.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index e4a4145..941bbc8 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -912,6 +912,7 @@ struct cgroup_subsys blkio_cgrp_subsys = {
.css_free = blkcg_css_free,
.can_attach = blkcg_can_attach,
.base_cftypes = blkcg_files,
+ .early_init = 0,
};
EXPORT_SYMBOL_GPL(blkio_cgrp_subsys);
--
2.0.0-rc0
--
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the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
