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Subject[PATCH 3/4] fs/inode.c: do not take i_lock when identify an inode
Date
Identity of an inode, which is defined by i_sb and i_ino or by individual
filesystem specific way, is not expected to be changed during inode's life
time. When identify an inode, taking i_lock _seems_ unnecessary. In source
code, we do have functions identifying an inode without i_lock held,
e.g. test_inode_iunique().

Then, fix those functions which take i_lock, e.g. find_inode_fast().

Note this change still put individual filesystem's test() method under
i_lock's protection. See next patch for more.

Signed-off-by: Guo Chao <yan@linux.vnet.ibm.com>
---
fs/inode.c | 16 +++++-----------
1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index 54e4b29..89d2bcc 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -786,11 +786,9 @@ static struct inode *find_inode(struct super_block *sb,

repeat:
hlist_for_each_entry(inode, node, head, i_hash) {
- spin_lock(&inode->i_lock);
- if (inode->i_sb != sb) {
- spin_unlock(&inode->i_lock);
+ if (inode->i_sb != sb)
continue;
- }
+ spin_lock(&inode->i_lock);
if (!test(inode, data)) {
spin_unlock(&inode->i_lock);
continue;
@@ -818,15 +816,11 @@ static struct inode *find_inode_fast(struct super_block *sb,

repeat:
hlist_for_each_entry(inode, node, head, i_hash) {
- spin_lock(&inode->i_lock);
- if (inode->i_ino != ino) {
- spin_unlock(&inode->i_lock);
+ if (inode->i_ino != ino)
continue;
- }
- if (inode->i_sb != sb) {
- spin_unlock(&inode->i_lock);
+ if (inode->i_sb != sb)
continue;
- }
+ spin_lock(&inode->i_lock);
if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
__wait_on_freeing_inode(inode);
goto repeat;
--
1.7.9.5


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