Quota inode is append only. In most cases writes performed
to allocated blocks before i_size. Currently we grup i_mutex
for each quota write to protect i_size and i_mtime. But in most
cases i_size not changed. And i_mtime is not that important
as for regular files. So let's update it only when quota file
increased. This allow us to avoid i_mutex in most cases.
Some day quota file will be hiden completly, so i_mtime hack
will disappear.
Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
---
fs/ext4/super.c | 22 +++++++++++++++-------
1 files changed, 15 insertions(+), 7 deletions(-)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b7b5707..5a378e3 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4039,6 +4039,7 @@ static ssize_t ext4_quota_write(struct super_block *sb, int type,
ext4_lblk_t blk = off >> EXT4_BLOCK_SIZE_BITS(sb);
int err = 0;
int offset = off & (sb->s_blocksize - 1);
+ int is_locked = 0;
int journal_quota = EXT4_SB(sb)->s_qf_names[type] != NULL;
struct buffer_head *bh;
handle_t *handle = journal_current_handle();
@@ -4059,8 +4060,14 @@ static ssize_t ext4_quota_write(struct super_block *sb, int type,
(unsigned long long)off, (unsigned long long)len);
return -EIO;
}
-
- mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA);
+ /*
+ * Inode file is append only. It is not necessery to hold i_mutex
+ * if quota block is allocated already. Optimize that case.
+ */
+ if (off + len > i_size_read(inode)) {
+ mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA);
+ is_locked = 1;
+ }
bh = ext4_bread(handle, inode, blk, 1, &err);
if (!bh)
goto out;
@@ -4085,16 +4092,17 @@ static ssize_t ext4_quota_write(struct super_block *sb, int type,
brelse(bh);
out:
if (err) {
- mutex_unlock(&inode->i_mutex);
+ if (is_locked)
+ mutex_unlock(&inode->i_mutex);
return err;
}
- if (inode->i_size < off + len) {
+ if (is_locked) {
i_size_write(inode, off + len);
EXT4_I(inode)->i_disksize = inode->i_size;
+ inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+ ext4_mark_inode_dirty(handle, inode);
+ mutex_unlock(&inode->i_mutex);
}
- inode->i_mtime = inode->i_ctime = CURRENT_TIME;
- ext4_mark_inode_dirty(handle, inode);
- mutex_unlock(&inode->i_mutex);
return len;
}
--
1.6.6.1
--
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