tgt_loop: Introduce device offset #89
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The format string in nbd_setup_tgt() lacks pragma for printing the last argument (send_zc) even though the variable is passed afterwards. Signed-off-by: Michal Privoznik <[email protected]>
The aim of ublksrv_json_read_target_ulong_info() is to fetch value corresponding to given key from JSON and return it in its last argument. But the last argument is of type long which contradicts not only the function name but also set function (ublksrv_json_write_target_ulong_info()). Switch the argument type to unsigned long. Signed-off-by: Michal Privoznik <[email protected]>
The intended way to store additional data associated with a target is via tgt_data pointer. So far, global variables are used which works, but gives bad example for anybody taking inspiration from our code. This also fixes a bug, where @block_device wasn't set during recovery, only in loop_init_tgt(). Signed-off-by: Michal Privoznik <[email protected]>
The aim of tgt_loop is to mimic losetup. Well, losetup allow users to move the start of loopback device given amount of bytes (-o/--offset arguments). Provide missing implementation. Signed-off-by: Michal Privoznik <[email protected]>
ming1
reviewed
Feb 2, 2025
| @@ -199,6 +226,17 @@ static int loop_init_tgt(struct ublksrv_dev *dev, int type, int argc, char | |||
| buffered_io = 1; | |||
| } | |||
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| if (bytes > 0) { | |||
| unsigned long long offset_bytes = offset * (1 << p.basic.physical_bs_shift); | |||
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From the helper message of offset skips first NUM sectors on backing file, here we should figure out offset_bytes via offset * 512, which is applied in IO code path too.
Otherwise, this PR looks good.
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Just like
losetupallows skipping first N bytes on the underlying file, let's have something similar fortgt_loop.