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Subject[ 128/184] ext4: fix race in ext4_mb_add_n_trim()
2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Niu Yawei <yawei.niu@gmail.com>

commit f1167009711032b0d747ec89a632a626c901a1ad upstream.

In ext4_mb_add_n_trim(), lg_prealloc_lock should be taken when
changing the lg_prealloc_list.

Signed-off-by: Niu Yawei <yawei.niu@intel.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
fs/ext4/mballoc.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 42bac1b..c7e8bdb 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4163,7 +4163,7 @@ static void ext4_mb_add_n_trim(struct ext4_allocation_context *ac)
/* The max size of hash table is PREALLOC_TB_SIZE */
order = PREALLOC_TB_SIZE - 1;
/* Add the prealloc space to lg */
- rcu_read_lock();
+ spin_lock(&lg->lg_prealloc_lock);
list_for_each_entry_rcu(tmp_pa, &lg->lg_prealloc_list[order],
pa_inode_list) {
spin_lock(&tmp_pa->pa_lock);
@@ -4187,12 +4187,12 @@ static void ext4_mb_add_n_trim(struct ext4_allocation_context *ac)
if (!added)
list_add_tail_rcu(&pa->pa_inode_list,
&lg->lg_prealloc_list[order]);
- rcu_read_unlock();
+ spin_unlock(&lg->lg_prealloc_lock);

/* Now trim the list to be not more than 8 elements */
if (lg_prealloc_count > 8) {
ext4_mb_discard_lg_preallocations(sb, lg,
- order, lg_prealloc_count);
+ order, lg_prealloc_count);
return;
}
return ;
--
1.7.12.2.21.g234cd45.dirty




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