On Tuesday 21 October 2014 at 18:33:11, Edward Shishkin wrote: > On 10/21/2014 06:23 PM, Ivan Shapovalov wrote: > > On Tuesday 21 October 2014 at 18:21:56, Edward Shishkin wrote: > >> [...] > >> > >> Sorry, but I don't see any explanation. > > "given a filesystem with (5% + eps) free space left, not using the reserved > > space will result in trimming of (eps) blocks at a time." > > > > > This is something that I am not able to parse :) > > Ok, it is clear, why we can not fail with -ENOSPC when trying to delete > a file from a full partition, yes? Sure. Please note that making reiser4_trim_fs's allocations BA_RESERVED will not hinder this: delete_mutex is there for a reason. > I want to see explanation, why FITRIM ioclt can not finish the work when > there is no free space on disk. Suppose we do not use reserved space for reiser4_trim_fs's allocations. Let's analyze those two cases: 1. There is <= 5% free space on disk. Initial grabbing fails, nothing can be trimmed. This is wrong. 2. There is 5% + X (where X is some small number) free space on disk. We can grab only X blocks at a time, so a total of ((SIZE * 5% / X) + 1) transactions will be created. BTW, if X < erase unit, nothing can be trimmed. This is ineffective. Hope this makes sense. -- Ivan Shapovalov / intelfx /
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