Surprisingly chown() on ext4 is not SMP scalable operation.
Due to unconditional orphan_del(NULL, inode) in ext4_setattr()
result in significant performance overhead because of global orphan
mutex, especially in no-journal mode (where orphan_add() is noop).
It is possible to skip explicit orphan_del if possible.
Results of fchown() micro-benchmark in no-journal mode
while (1) {
iteration++;
fchown(fd, uid, gid);
fchown(fd, uid + 1, gid + 1)
}
measured: iterations per millisecond
| nr_tasks | w/o patch | with patch |
| 1 | 142 | 185 |
| 4 | 109 | 642 |
Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
---
fs/ext4/inode.c | 10 +++++++---
1 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 18eed80..a16097b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5540,6 +5540,7 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = dentry->d_inode;
int error, rc = 0;
+ int orphan = 0;
const unsigned int ia_valid = attr->ia_valid;
error = inode_change_ok(inode, attr);
@@ -5595,8 +5596,10 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
error = PTR_ERR(handle);
goto err_out;
}
-
- error = ext4_orphan_add(handle, inode);
+ if (ext4_handle_valid(handle)) {
+ error = ext4_orphan_add(handle, inode);
+ orphan = 1;
+ }
EXT4_I(inode)->i_disksize = attr->ia_size;
rc = ext4_mark_inode_dirty(handle, inode);
if (!error)
@@ -5608,6 +5611,7 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
attr->ia_size);
if (error) {
/* Do as much error cleanup as possible */
+ orphan = 0;
handle = ext4_journal_start(inode, 3);
if (IS_ERR(handle)) {
ext4_orphan_del(NULL, inode);
@@ -5636,7 +5640,7 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
* If the call to ext4_truncate failed to get a transaction handle at
* all, we need to clean up the in-core orphan list manually.
*/
- if (inode->i_nlink)
+ if (orphan && inode->i_nlink)
ext4_orphan_del(NULL, inode);
if (!rc && (ia_valid & ATTR_MODE))
--
1.6.6.1
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