On 10/21/2014 12:39 AM, Ivan Shapovalov wrote:
On Monday 20 October 2014 at 12:54:13, Edward Shishkin wrote:
On 08/17/2014 11:52 PM, Ivan Shapovalov wrote:
[...]
+ /*
+ * Grab some sane amount of space.
+ * We will allocate blocks until end of the partition or until
+ * the grabbed space is exhausted.
+ */
+ ret = reiser4_grab_reserved(super, 0, BA_CAN_COMMIT | BA_SOME_SPACE);
reiser4_grab_reserved() grabs space from the reserved area (5%).
This is needed to make sure that unlink(), truncate(), etc. won't
fail, if there is no free space on disk. I don't think that FITRIM
ioctl needs this reserved area.
Well, IIUC, it doesn't hurt:
"doesn't hurt" is not enough. If you want to take a resource,
you should be going to explain, why do you need this.
any "legitimate" user of the reserved space
will block on the mutex and eventually proceed. At the same time, given
a filesystem with (5% + eps) free space left, not using the reserved space
will result in trimming of (eps) blocks at a time.
Anyway, I should also fix calculation of space to grab in 1/9: if BA_RESERVED
is not set, then the amount to grab should be calculated as 25% of non-reserved
free space, not as 25% of all free space...
If BA_SOME_SPACE is set, then you lock a superblock, and grab 25% of
the current free space. It means that your grab will always succeed,
so that BA_CAN_COMMIT flag is also not needed.
If we decide on dropping BA_RESERVED, then you're right here;
reiser4_grab(...BA_SOME_SPACE...) won't return ENOSPC and so this is pointless.
If we decide on keeping BA_RESERVED, then this should also stay in order not to
trigger the assertion.
Thanks,
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