[PATCH] list_for_each_rcu must die: ext4

From: Paul E. McKenney
Date: Wed Apr 23 2008 - 21:27:29 EST


All uses of list_for_each_rcu() can be profitably replaced by the
easier-to-use list_for_each_entry_rcu(). This patch makes this change for
the ext4 filesystem, in preparation for removing the list_for_each_rcu()
API entirely.

Signed_off_by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---

mballoc.c | 33 +++++++++------------------------
1 file changed, 9 insertions(+), 24 deletions(-)

diff -urpNa -X dontdiff linux-2.6.25/fs/ext4/mballoc.c linux-2.6.25-lfer-ext/fs/ext4/mballoc.c
--- linux-2.6.25/fs/ext4/mballoc.c 2008-04-16 19:49:44.000000000 -0700
+++ linux-2.6.25-lfer-ext/fs/ext4/mballoc.c 2008-04-23 16:42:12.000000000 -0700
@@ -819,7 +819,7 @@ static int __mb_check_buddy(struct ext4_
struct ext4_group_info *grp;
int fragments = 0;
int fstart;
- struct list_head *cur;
+ struct ext4_prealloc_space *pa;
void *buddy;
void *buddy2;

@@ -895,10 +895,8 @@ static int __mb_check_buddy(struct ext4_

grp = ext4_get_group_info(sb, e4b->bd_group);
buddy = mb_find_buddy(e4b, 0, &max);
- list_for_each(cur, &grp->bb_prealloc_list) {
+ list_for_each_entry(pa, &grp->bb_prealloc_list, group_list) {
ext4_group_t groupnr;
- struct ext4_prealloc_space *pa;
- pa = list_entry(cur, struct ext4_prealloc_space, group_list);
ext4_get_group_no_and_offset(sb, pa->pstart, &groupnr, &k);
MB_CHECK_ASSERT(groupnr == e4b->bd_group);
for (i = 0; i < pa->len; i++)
@@ -3151,7 +3149,7 @@ static void ext4_mb_normalize_request(st
{
int bsbits, max;
ext4_lblk_t end;
- struct list_head *cur;
+ struct ext4_prealloc_space *pa;
loff_t size, orig_size, start_off;
ext4_lblk_t start, orig_start;
struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
@@ -3240,12 +3238,9 @@ static void ext4_mb_normalize_request(st

/* check we don't cross already preallocated blocks */
rcu_read_lock();
- list_for_each_rcu(cur, &ei->i_prealloc_list) {
- struct ext4_prealloc_space *pa;
+ list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
unsigned long pa_end;

- pa = list_entry(cur, struct ext4_prealloc_space, pa_inode_list);
-
if (pa->pa_deleted)
continue;
spin_lock(&pa->pa_lock);
@@ -3287,10 +3282,8 @@ static void ext4_mb_normalize_request(st

/* XXX: extra loop to check we really don't overlap preallocations */
rcu_read_lock();
- list_for_each_rcu(cur, &ei->i_prealloc_list) {
- struct ext4_prealloc_space *pa;
+ list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {
unsigned long pa_end;
- pa = list_entry(cur, struct ext4_prealloc_space, pa_inode_list);
spin_lock(&pa->pa_lock);
if (pa->pa_deleted == 0) {
pa_end = pa->pa_lstart + pa->pa_len;
@@ -3417,7 +3410,6 @@ static int ext4_mb_use_preallocated(stru
struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
struct ext4_locality_group *lg;
struct ext4_prealloc_space *pa;
- struct list_head *cur;

/* only data can be preallocated */
if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
@@ -3425,8 +3417,7 @@ static int ext4_mb_use_preallocated(stru

/* first, try per-file preallocation */
rcu_read_lock();
- list_for_each_rcu(cur, &ei->i_prealloc_list) {
- pa = list_entry(cur, struct ext4_prealloc_space, pa_inode_list);
+ list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {

/* all fields in this condition don't change,
* so we can skip locking for them */
@@ -3458,8 +3449,7 @@ static int ext4_mb_use_preallocated(stru
return 0;

rcu_read_lock();
- list_for_each_rcu(cur, &lg->lg_prealloc_list) {
- pa = list_entry(cur, struct ext4_prealloc_space, pa_inode_list);
+ list_for_each_entry_rcu(pa, &lg->lg_prealloc_list, pa_inode_list) {
spin_lock(&pa->pa_lock);
if (pa->pa_deleted == 0 && pa->pa_free >= ac->ac_o_ex.fe_len) {
atomic_inc(&pa->pa_count);
@@ -3486,7 +3476,6 @@ static void ext4_mb_generate_from_pa(str
{
struct ext4_group_info *grp = ext4_get_group_info(sb, group);
struct ext4_prealloc_space *pa;
- struct list_head *cur;
ext4_group_t groupnr;
ext4_grpblk_t start;
int preallocated = 0;
@@ -3501,8 +3490,7 @@ static void ext4_mb_generate_from_pa(str
* allocation in buddy when concurrent ext4_mb_put_pa()
* is dropping preallocation
*/
- list_for_each(cur, &grp->bb_prealloc_list) {
- pa = list_entry(cur, struct ext4_prealloc_space, pa_group_list);
+ list_for_each_entry(pa, &grp->bb_prealloc_list, pa_group_list) {
spin_lock(&pa->pa_lock);
ext4_get_group_no_and_offset(sb, pa->pa_pstart,
&groupnr, &start);
@@ -4104,11 +4092,8 @@ static void ext4_mb_show_ac(struct ext4_
struct ext4_group_info *grp = ext4_get_group_info(sb, i);
struct ext4_prealloc_space *pa;
ext4_grpblk_t start;
- struct list_head *cur;
ext4_lock_group(sb, i);
- list_for_each(cur, &grp->bb_prealloc_list) {
- pa = list_entry(cur, struct ext4_prealloc_space,
- pa_group_list);
+ list_for_each_entry(pa, &grp->bb_prealloc_list, pa_group_list) {
spin_lock(&pa->pa_lock);
ext4_get_group_no_and_offset(sb, pa->pa_pstart,
NULL, &start);
--
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