JunChao Sun <sunjunchao2870@xxxxxxxxx> 于2023年5月9日周二 09:10写道： > > When replace the value of xattr which found in an ea_inode, currently > ext4 will evict ea_inode which stores the old value, recreate an > ea_inode and then write the new value into new ea_inode. This can > be optimized by writing the new value into old ea_inode directly. > > The logic for replacing the value of xattr without this patch > is as follows: > ext4_xattr_set_entry() > ->ext4_xattr_inode_iget(&old_ea_inode) > ->ext4_xattr_inode_lookup_create(&new_ea_inode) > ->ext4_xattr_inode_dec_ref(old_ea_inode) > ->iput(old_ea_inode) > ->ext4_destroy_inode() > ->ext4_evict_inode() > ->ext4_free_inode() > ->iput(new_ea_inode) > > The logic with this patch is: > ext4_xattr_set_entry() > ->ext4_xattr_inode_iget(&old_ea_inode) > ->ext4_xattr_inode_write(old_ea_inode, new_value) > ->iput(old_ea_inode) > > This patch reduces the time it takes to replace xattr in ext4. > Without this patch, replacing the value of xattr two million times takes > about 45 seconds on Intel(R) Xeon(R) CPU E5-2620 v3 platform. > With this patch, the same operation takes only 6 seconds. > > [root@client01 sjc]# ./mount.sh > /dev/sdb1 contains a ext4 file system > last mounted on /mnt/ext4 on Mon May 8 17:05:38 2023 > [root@client01 sjc]# touch /mnt/ext4/file1 > [root@client01 sjc]# gcc test.c > [root@client01 sjc]# time ./a.out > > real 0m45.248s > user 0m0.513s > sys 0m39.231s > > [root@client01 sjc]# ./mount.sh > /dev/sdb1 contains a ext4 file system > last mounted on /mnt/ext4 on Mon May 8 17:08:20 2023 > [root@client01 sjc]# touch /mnt/ext4/file1 > [root@client01 sjc]# time ./a.out > > real 0m5.977s > user 0m0.316s > sys 0m5.659s > > The test.c and mount.sh are in [1]. > This patch passed the tests with xfstests using 'check -g quick'. > > [1]: https://gist.github.com/sjc2870/c923d7fa627d10ab65d6c305afb02cdb > > Signed-off-by: JunChao Sun <sunjunchao2870@xxxxxxxxx> > --- > fs/ext4/xattr.c | 33 +++++++++++++++++++++++++++++++++ > 1 file changed, 33 insertions(+) > > diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c > index d57408cbe903..37f79594ac70 100644 > --- a/fs/ext4/xattr.c > +++ b/fs/ext4/xattr.c > @@ -1713,6 +1713,39 @@ static int ext4_xattr_set_entry(struct ext4_xattr_info *i, > } > } > > + if (!s->not_found && i->value && here->e_value_inum && i->in_inode) { > + /* Replace xattr value in ea_inode in place */ > + int size_diff = i->value_len - le32_to_cpu(here->e_value_size); > + > + ret = ext4_xattr_inode_iget(inode, > + le32_to_cpu(here->e_value_inum), > + le32_to_cpu(here->e_hash), > + &old_ea_inode); > + if (ret) { > + old_ea_inode = NULL; > + goto out; > + } > > > + if (size_diff > 0) > > + ret = ext4_xattr_inode_alloc_quota(inode, size_diff); > > + else if (size_diff < 0) > > + ext4_xattr_inode_free_quota(inode, NULL, -size_diff); > > + if (ret) > > + goto out; > > + > > + ret = ext4_xattr_inode_write(handle, old_ea_inode, i->value, i->value_len); > > + if (ret) { > > + if (size_diff > 0) > > + ext4_xattr_inode_free_quota(inode, NULL, size_diff); > > + else if (size_diff < 0) > > + ret = ext4_xattr_inode_alloc_quota(inode, -size_diff); > > + goto out; > > + } Here might missed a judgment condition: if (ext4_xattr_inodee_get_ref(old_ea_inode) == 1). I will send patch v2 to fix this. > + here->e_value_size = cpu_to_le32(i->value_len); > + new_ea_inode = old_ea_inode; > + old_ea_inode = NULL; > + goto update_hash; > + } > + > /* > * Getting access to old and new ea inodes is subject to failures. > * Finish that work before doing any modifications to the xattr data. > -- > 1.8.3.1 >
