dm: document iterate_devices
Document iterate_devices in device-mapper.h. Signed-off-by: Alasdair G Kergon <agk@redhat.com>
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@ -79,11 +79,26 @@ typedef int (*dm_ioctl_fn) (struct dm_target *ti, unsigned int cmd,
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typedef int (*dm_merge_fn) (struct dm_target *ti, struct bvec_merge_data *bvm,
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typedef int (*dm_merge_fn) (struct dm_target *ti, struct bvec_merge_data *bvm,
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struct bio_vec *biovec, int max_size);
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struct bio_vec *biovec, int max_size);
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/*
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* These iteration functions are typically used to check (and combine)
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* properties of underlying devices.
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* E.g. Does at least one underlying device support flush?
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* Does any underlying device not support WRITE_SAME?
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*
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* The callout function is called once for each contiguous section of
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* an underlying device. State can be maintained in *data.
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* Return non-zero to stop iterating through any further devices.
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*/
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typedef int (*iterate_devices_callout_fn) (struct dm_target *ti,
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typedef int (*iterate_devices_callout_fn) (struct dm_target *ti,
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struct dm_dev *dev,
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struct dm_dev *dev,
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sector_t start, sector_t len,
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sector_t start, sector_t len,
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void *data);
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void *data);
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/*
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* This function must iterate through each section of device used by the
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* target until it encounters a non-zero return code, which it then returns.
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* Returns zero if no callout returned non-zero.
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*/
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typedef int (*dm_iterate_devices_fn) (struct dm_target *ti,
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typedef int (*dm_iterate_devices_fn) (struct dm_target *ti,
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iterate_devices_callout_fn fn,
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iterate_devices_callout_fn fn,
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void *data);
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void *data);
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