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authorRoger Pau Monne <roger.pau@citrix.com>2013-06-21 12:56:53 +0200
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2013-06-21 15:58:44 -0400
commit2d9105433ff471d2c688817e98804029c074a623 (patch)
tree7794f24be80ffaad203616bf71162bc6b54c133f /drivers/block/xen-blkback
parent8e3f8755545cc4a7f4da8e9ef76d6d32e0dca576 (diff)
downloadblackbird-op-linux-2d9105433ff471d2c688817e98804029c074a623.tar.gz
blackbird-op-linux-2d9105433ff471d2c688817e98804029c074a623.zip
xen-blkback: workaround compiler bug in gcc 4.1
The code generat with gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-54) creates an unbound loop for the second foreach_grant_safe loop in purge_persistent_gnt. The workaround is to avoid having this second loop and instead perform all the work inside the first loop by adding a new variable, clean_used, that will be set when all the desired persistent grants have been removed and we need to iterate over the remaining ones to remove the WAS_ACTIVE flag. Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> Reported-by: Tom O'Neill <toneill@vmem.com> Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Diffstat (limited to 'drivers/block/xen-blkback')
-rw-r--r--drivers/block/xen-blkback/blkback.c24
1 files changed, 14 insertions, 10 deletions
diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index ea158fe0c9a4..4662217c61be 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -341,7 +341,7 @@ static void purge_persistent_gnt(struct xen_blkif *blkif)
struct persistent_gnt *persistent_gnt;
struct rb_node *n;
unsigned int num_clean, total;
- bool scan_used = false;
+ bool scan_used = false, clean_used = false;
struct rb_root *root;
if (blkif->persistent_gnt_c < xen_blkif_max_pgrants ||
@@ -358,9 +358,8 @@ static void purge_persistent_gnt(struct xen_blkif *blkif)
num_clean = (xen_blkif_max_pgrants / 100) * LRU_PERCENT_CLEAN;
num_clean = blkif->persistent_gnt_c - xen_blkif_max_pgrants + num_clean;
num_clean = min(blkif->persistent_gnt_c, num_clean);
- if (num_clean >
- (blkif->persistent_gnt_c -
- atomic_read(&blkif->persistent_gnt_in_use)))
+ if ((num_clean == 0) ||
+ (num_clean > (blkif->persistent_gnt_c - atomic_read(&blkif->persistent_gnt_in_use))))
return;
/*
@@ -383,6 +382,11 @@ purge_list:
BUG_ON(persistent_gnt->handle ==
BLKBACK_INVALID_HANDLE);
+ if (clean_used) {
+ clear_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
+ continue;
+ }
+
if (test_bit(PERSISTENT_GNT_ACTIVE, persistent_gnt->flags))
continue;
if (!scan_used &&
@@ -400,18 +404,18 @@ purge_list:
* grants that were used since last purge in order to cope
* with the requested num
*/
- if (!scan_used) {
+ if (!scan_used && !clean_used) {
pr_debug(DRV_PFX "Still missing %u purged frames\n", num_clean);
scan_used = true;
goto purge_list;
}
finished:
- /* Remove the "used" flag from all the persistent grants */
- foreach_grant_safe(persistent_gnt, n, root, node) {
- BUG_ON(persistent_gnt->handle ==
- BLKBACK_INVALID_HANDLE);
- clear_bit(PERSISTENT_GNT_WAS_ACTIVE, persistent_gnt->flags);
+ if (!clean_used) {
+ pr_debug(DRV_PFX "Finished scanning for grants to clean, removing used flag\n");
+ clean_used = true;
+ goto purge_list;
}
+
blkif->persistent_gnt_c -= (total - num_clean);
blkif->vbd.overflow_max_grants = 0;
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