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ocfs2: make ocfs2_adjust_resv_from_alloc simple.

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When we allocate some bits from the reservation, we always
allocate from the r_start(see ocfs2_resmap_resv_bits).
So there should be no reason to check between r_start
and start. And I don't think we will change this behaviour
later by allocating from some bits after r_start.  Why not make
ocfs2_adjust_resv_from_alloc simple for now?

The only chance we have to adjust the reservation is when we haven't
reached the end. With this patch, the function is more readable.

Note:
btw, this patch also fixes an original bug in the function
which I haven't found before.
	if (end < ocfs2_resv_end(resv))
		rhs = end - ocfs2_resv_end(resv);
This code is of course buggy. ;)

Signed-off-by: Tao Ma <tao.ma@oracle.com>
Acked-by: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
This commit is contained in:
Tao Ma 2010-04-08 16:33:02 +08:00 committed by Joel Becker
parent 4b37fcb7d4
commit b065556a7d
2 changed files with 14 additions and 21 deletions
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32
fs/ocfs2/reservations.c
View file

@ -408,7 +408,7 @@ ocfs2_find_resv_lhs(struct ocfs2_reservation_map *resmap, unsigned int goal)
* The start value of *rstart is insignificant.
*
* This function searches the bitmap range starting at search_start
* with length csearch_len for a set of contiguous free bits. We try
* with length search_len for a set of contiguous free bits. We try
* to find up to 'wanted' bits, but can sometimes return less.
*
* Returns the length of allocation, 0 if no free bits are found.
@ -778,38 +778,28 @@ static void
struct ocfs2_alloc_reservation *resv,
unsigned int start, unsigned int end)
{
unsigned int lhs = 0, rhs = 0;
unsigned int rhs = 0;
unsigned int old_end = ocfs2_resv_end(resv);
BUG_ON(start < resv->r_start);
BUG_ON(start != resv->r_start || old_end < end);
/*
* Completely used? We can remove it then.
*/
if (ocfs2_resv_end(resv) <= end && resv->r_start >= start) {
if (old_end == end) {
__ocfs2_resv_discard(resmap, resv);
return;
}
if (end < ocfs2_resv_end(resv))
rhs = end - ocfs2_resv_end(resv);
if (start > resv->r_start)
lhs = start - resv->r_start;
rhs = old_end - end;
/*
* This should have been trapped above. At the very least, rhs
* should be non zero.
* This should have been trapped above.
*/
BUG_ON(rhs == 0 && lhs == 0);
BUG_ON(rhs == 0);
if (rhs >= lhs) {
unsigned int old_end = ocfs2_resv_end(resv);
resv->r_start = end + 1;
resv->r_len = old_end - resv->r_start + 1;
} else {
resv->r_len = start - resv->r_start;
}
resv->r_start = end + 1;
resv->r_len = old_end - resv->r_start + 1;
}
void ocfs2_resmap_claimed_bits(struct ocfs2_reservation_map *resmap,
@ -824,6 +814,8 @@ void ocfs2_resmap_claimed_bits(struct ocfs2_reservation_map *resmap,
if (resv == NULL)
return;
BUG_ON(cstart != resv->r_start);
spin_lock(&resv_lock);
mlog(0, "claim bits: cstart: %u cend: %u clen: %u r_start: %u "

3
fs/ocfs2/reservations.h
View file

@ -149,7 +149,8 @@ int ocfs2_resmap_resv_bits(struct ocfs2_reservation_map *resmap,
* reservation. But we must always call this function when bits are claimed.
* Internally, the reservations code will use this information to mark the
* reservations bitmap. If resv is passed, it's next allocation window will be
* calculated.
* calculated. It also expects that 'cstart' is the same as we passed back
* from ocfs2_resmap_resv_bits().
*/
void ocfs2_resmap_claimed_bits(struct ocfs2_reservation_map *resmap,
struct ocfs2_alloc_reservation *resv,