get_new_segment is too unclear to understand how it works.
This patch refactor it in a straight-forward way and
I think it is equal to the original one.
This patch also fixes two issues in the original get_new_segment:
1) left_start could be overflowed when hint == 0 at first:
...
} else {
go_left = 1;
* left_start = hint - 1;
}
...
* while (test_bit(left_start, free_i->free_secmap)) {
2) It will do find_next_zero_bit again when go_left == true and ALLOC_LEFT:
...
find_other_zone:
* secno = find_next_zero_bit(free_i->free_secmap, MAIN_SECS(sbi), hint);
if (secno >= MAIN_SECS(sbi)) {
if (dir == ALLOC_RIGHT) {
...
} else {
go_left = 1;
...
}
}
if (go_left == 0)
goto skip_left;
...
if (i < NR_CURSEG_TYPE) {
/* zone is in user, try another */
* if (go_left)
* hint = zoneno * sbi->secs_per_zone - 1;
...
init = false;
goto find_other_zone;
}
Signed-off-by: Gao Xiang <hsiang...@aol.com>
---
fs/f2fs/segment.c | 137 ++++++++++++++++++++++++++++++++----------------------
1 file changed, 81 insertions(+), 56 deletions(-)
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index c117e09..eea9d3f 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2047,82 +2047,107 @@ static void get_new_segment(struct f2fs_sb_info *sbi,
unsigned int *newseg, bool new_sec, int dir)
{
struct free_segmap_info *free_i = FREE_I(sbi);
- unsigned int segno, secno, zoneno;
+ unsigned int segno = *newseg, zoneno;
+ unsigned int secno = GET_SEC_FROM_SEG(sbi, segno);
unsigned int total_zones = MAIN_SECS(sbi) / sbi->secs_per_zone;
- unsigned int hint = GET_SEC_FROM_SEG(sbi, *newseg);
- unsigned int old_zoneno = GET_ZONE_FROM_SEG(sbi, *newseg);
- unsigned int left_start = hint;
- bool init = true;
- int go_left = 0;
+ unsigned int old_zoneno = GET_ZONE_FROM_SEC(sbi, secno);
+ bool may_again = true, actually_go_left = false;
int i;
spin_lock(&free_i->segmap_lock);
- if (!new_sec && ((*newseg + 1) % sbi->segs_per_sec)) {
+ /* first, attempt to find a segment in the current section */
+ if (!new_sec && ((segno + 1) % sbi->segs_per_sec)) {
+ unsigned end_segno = GET_SEG_FROM_SEC(sbi, secno + 1);
+
segno = find_next_zero_bit(free_i->free_segmap,
- GET_SEG_FROM_SEC(sbi, hint + 1), *newseg + 1);
- if (segno < GET_SEG_FROM_SEC(sbi, hint + 1))
- goto got_it;
+ end_segno, segno + 1);
+
+ if (segno < end_segno)
+ goto out;
}
-find_other_zone:
- secno = find_next_zero_bit(free_i->free_secmap, MAIN_SECS(sbi), hint);
- if (secno >= MAIN_SECS(sbi)) {
- if (dir == ALLOC_RIGHT) {
- secno = find_next_zero_bit(free_i->free_secmap,
- MAIN_SECS(sbi), 0);
- f2fs_bug_on(sbi, secno >= MAIN_SECS(sbi));
- } else {
- go_left = 1;
- left_start = hint - 1;
+
+try_another_section:
+ if (likely(!actually_go_left)) {
+ /*
+ * since ALLOC_LEFT takes much effort,
+ * prefer to ALLOC_RIGHT first
+ */
+ unsigned int new_secno = find_next_zero_bit(
+ free_i->free_secmap, MAIN_SECS(sbi), secno);
+
+ if (new_secno < MAIN_SECS(sbi)) {
+ secno = new_secno;
+ goto check_another_zone;
}
}
- if (go_left == 0)
- goto skip_left;
- while (test_bit(left_start, free_i->free_secmap)) {
- if (left_start > 0) {
- left_start--;
- continue;
- }
- left_start = find_next_zero_bit(free_i->free_secmap,
- MAIN_SECS(sbi), 0);
- f2fs_bug_on(sbi, left_start >= MAIN_SECS(sbi));
- break;
+ if (dir == ALLOC_LEFT) {
+ /* ALLOC_LEFT, no free sections on the right side */
+ actually_go_left = true;
+
+ while(secno)
+ if (!test_bit(--secno, free_i->free_secmap))
+ goto check_another_zone;
}
- secno = left_start;
-skip_left:
- segno = GET_SEG_FROM_SEC(sbi, secno);
- zoneno = GET_ZONE_FROM_SEC(sbi, secno);
+ /*
+ * when ALLOC_RIGHT and secno >= end_endno
+ * or ALLOC_LEFT and secno == 0, we need do the last attempt
+ * since the function should be returned with success
+ */
+ secno = find_next_zero_bit(free_i->free_secmap, MAIN_SECS(sbi), 0);
+ f2fs_bug_on(sbi, secno >= MAIN_SECS(sbi));
+
+check_another_zone:
/* give up on finding another zone */
- if (!init)
- goto got_it;
- if (sbi->secs_per_zone == 1)
+ if (!may_again || sbi->secs_per_zone == 1)
goto got_it;
+
+ zoneno = GET_ZONE_FROM_SEC(sbi, secno);
if (zoneno == old_zoneno)
goto got_it;
- if (dir == ALLOC_LEFT) {
- if (!go_left && zoneno + 1 >= total_zones)
- goto got_it;
- if (go_left && zoneno == 0)
+
+ /*
+ * since the following case will be likely to frequently happen,
+ * leave it here rather than put together in the following loop
+ */
+ if (dir == ALLOC_LEFT)
+ /*
+ * I'm really confused why not select
+ * zoneno * sbi->secs_per_zone - 1 in this case.
+ * Okay, leave it as the origin
+ */
+ if (!actually_go_left && zoneno + 1 >= total_zones)
goto got_it;
- }
+
for (i = 0; i < NR_CURSEG_TYPE; i++)
- if (CURSEG_I(sbi, i)->zone == zoneno)
- break;
+ /* the zone is in use, try another */
+ if (CURSEG_I(sbi, i)->zone == zoneno) {
+ /* try the neighbor (left or right) zone */
+ if (actually_go_left) {
+ /*
+ * since ALLOC_LEFT and no way to get free on
+ * the right side, it's safe to try the left
+ * zone and won't find the same section again.
+ */
+ if (zoneno == 0)
+ break;
+ secno = zoneno * sbi->secs_per_zone - 1;
+ } else if (zoneno + 1 >= total_zones) {
+ /* no way dir == ALLOC_LEFT at this time */
+ secno = 0;
+ } else
+ secno = (zoneno + 1) * sbi->secs_per_zone;
+
+ /* try another zone once at most */
+ may_again = false;
+ goto try_another_section;
+ }
- if (i < NR_CURSEG_TYPE) {
- /* zone is in user, try another */
- if (go_left)
- hint = zoneno * sbi->secs_per_zone - 1;
- else if (zoneno + 1 >= total_zones)
- hint = 0;
- else
- hint = (zoneno + 1) * sbi->secs_per_zone;
- init = false;
- goto find_other_zone;
- }
got_it:
+ segno = GET_SEG_FROM_SEC(sbi, secno);
+out:
/* set it as dirty segment in free segmap */
f2fs_bug_on(sbi, test_bit(segno, free_i->free_segmap));
__set_inuse(sbi, segno);
--
2.7.4
------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
