Help two questions about update_global_block_rsv()
update_global_block_rsv(fs_info) {
...
block_rsv = &fs_info->global_block_rsv;
sinfo = block_rsv->space_info;
num_bytes = sinfo->bytes_used + sinfo->bytes_pinned +
sinfo->bytes_reserved + sinfo->bytes_readonly +
sinfo->bytes_may_use;
if (sinfo->total_bytes > num_bytes) {
num_bytes = sinfo->total_bytes - num_bytes;
block_rsv->reserved += num_bytes;
sinfo->bytes_may_use += num_bytes;
}
...
}
1. I don't quite understand the lines:
block_rsv->reserved += num_bytes;
sinfo->bytes_may_use += num_bytes;
why aren't they like these?
block_rsv->reserved = num_bytes;
sinfo->bytes_may_use = num_bytes;
assuming that nothing else is changed, and we just call
update_global_block_rsv() for several times, then block_rsv->reserved will
increase constantly, and so sinfo->bytes_may_use; can anyone tell me what it
means? I mean if nothing else is changed the two variables should keep their
values unchanged also, is that right? a bit puzzlement to me.
2. Is the meaning of sinfo->bytes_may_use that bytes which is available for use
or that bytes which will likely/unlikely be used?
thanks
WeiFeng Liu
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