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Subject[RFC][PATCH 1/10] I/O context inheritance
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Make every bio points the iocontext of the process which originally
generated an I/O request.
- Assign the iocontext of the current process to a bio when it is
newly allocated.
- Assign the iocontext which the source bio has to a newly allocated
bio when it is duplicated.


Signed-off-by: Hirokazu Takahashi <taka@valinux.co.jp>


--- linux-2.6.25.bio0/include/linux/bio.h 2008-04-22 15:48:36.000000000 +0900
+++ linux-2.6.25/include/linux/bio.h 2008-04-22 15:49:42.000000000 +0900
@@ -114,6 +114,8 @@ struct bio {
void *bi_private;

bio_destructor_t *bi_destructor; /* destructor */
+
+ struct io_context *bi_io_context;
};

/*
--- linux-2.6.25.bio0/include/linux/iocontext.h 2008-04-22 15:48:36.000000000 +0900
+++ linux-2.6.25/include/linux/iocontext.h 2008-04-22 15:49:42.000000000 +0900
@@ -85,7 +85,7 @@ struct io_context {
void *ioc_data;
};

-static inline struct io_context *ioc_task_link(struct io_context *ioc)
+static inline struct io_context *ioc_object_link(struct io_context *ioc)
{
/*
* if ref count is zero, don't allow sharing (ioc is going away, it's
@@ -99,4 +99,6 @@ static inline struct io_context *ioc_tas
return NULL;
}

+#define ioc_task_link(ioc) ioc_object_link(ioc)
+
#endif
--- linux-2.6.25.bio0/fs/bio.c 2008-04-22 15:48:31.000000000 +0900
+++ linux-2.6.25/fs/bio.c 2008-04-22 15:49:42.000000000 +0900
@@ -107,8 +107,16 @@ static inline struct bio_vec *bvec_alloc
return bvl;
}

+static inline void put_bio_context(struct bio *bio)
+{
+ if (bio->bi_io_context)
+ put_io_context(bio->bi_io_context);
+}
+
void bio_free(struct bio *bio, struct bio_set *bio_set)
{
+ put_bio_context(bio);
+
if (bio->bi_io_vec) {
const int pool_idx = BIO_POOL_IDX(bio);

@@ -177,10 +185,29 @@ out:

struct bio *bio_alloc(gfp_t gfp_mask, int nr_iovecs)
{
- struct bio *bio = bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);
+ struct bio *bio;
+ struct io_context *ioc;

- if (bio)
+ /*
+ * Set the io_context of the current process here since this newly
+ * created bio may be passed to a I/O scheduler through another
+ * kernel thread in half of the process that originate this bio.
+ * get_io_context function should called here so it can be blocked
+ * in it.
+ * Todo: when the current is an aio kernel thread, the io_context
+ * of the original process should be set instead of that of
+ * the thread.
+ */
+ ioc = get_io_context(gfp_mask, -1);
+ if (!ioc)
+ return NULL;
+
+ bio = bio_alloc_bioset(gfp_mask, nr_iovecs, fs_bio_set);
+ if (bio) {
bio->bi_destructor = bio_fs_destructor;
+ bio->bi_io_context = ioc;
+ } else
+ put_io_context(ioc);

return bio;
}
@@ -262,6 +289,7 @@ void __bio_clone(struct bio *bio, struct
bio->bi_vcnt = bio_src->bi_vcnt;
bio->bi_size = bio_src->bi_size;
bio->bi_idx = bio_src->bi_idx;
+ bio->bi_io_context = ioc_object_link(bio_src->bi_io_context);
}

/**

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