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linux-next/fs/btrfs/xattr.c
Filipe Manana f2f121ab50 btrfs: skip unnecessary searches for xattrs when logging an inode
Every time we log an inode we lookup in the fs/subvol tree for xattrs and
if we have any, log them into the log tree. However it is very common to
have inodes without any xattrs, so doing the search wastes times, but more
importantly it adds contention on the fs/subvol tree locks, either making
the logging code block and wait for tree locks or making the logging code
making other concurrent operations block and wait.

The most typical use cases where xattrs are used are when capabilities or
ACLs are defined for an inode, or when SELinux is enabled.

This change makes the logging code detect when an inode does not have
xattrs and skip the xattrs search the next time the inode is logged,
unless the inode is evicted and loaded again or a xattr is added to the
inode. Therefore skipping the search for xattrs on inodes that don't ever
have xattrs and are fsynced with some frequency.

The following script that calls dbench was used to measure the impact of
this change on a VM with 8 CPUs, 16Gb of ram, using a raw NVMe device
directly (no intermediary filesystem on the host) and using a non-debug
kernel (default configuration on Debian distributions):

  $ cat test.sh
  #!/bin/bash

  DEV=/dev/sdk
  MNT=/mnt/sdk
  MOUNT_OPTIONS="-o ssd"

  mkfs.btrfs -f -m single -d single $DEV
  mount $MOUNT_OPTIONS $DEV $MNT

  dbench -D $MNT -t 200 40

  umount $MNT

The results before this change:

 Operation      Count    AvgLat    MaxLat
 ----------------------------------------
 NTCreateX    5761605     0.172   312.057
 Close        4232452     0.002    10.927
 Rename        243937     1.406   277.344
 Unlink       1163456     0.631   298.402
 Deltree          160    11.581   221.107
 Mkdir             80     0.003     0.005
 Qpathinfo    5221410     0.065   122.309
 Qfileinfo     915432     0.001     3.333
 Qfsinfo       957555     0.003     3.992
 Sfileinfo     469244     0.023    20.494
 Find         2018865     0.448   123.659
 WriteX       2874851     0.049   118.529
 ReadX        9030579     0.004    21.654
 LockX          18754     0.003     4.423
 UnlockX        18754     0.002     0.331
 Flush         403792    10.944   359.494

Throughput 908.444 MB/sec  40 clients  40 procs  max_latency=359.500 ms

The results after this change:

 Operation      Count    AvgLat    MaxLat
 ----------------------------------------
 NTCreateX    6442521     0.159   230.693
 Close        4732357     0.002    10.972
 Rename        272809     1.293   227.398
 Unlink       1301059     0.563   218.500
 Deltree          160     7.796    54.887
 Mkdir             80     0.008     0.478
 Qpathinfo    5839452     0.047   124.330
 Qfileinfo    1023199     0.001     4.996
 Qfsinfo      1070760     0.003     5.709
 Sfileinfo     524790     0.033    21.765
 Find         2257658     0.314   125.611
 WriteX       3211520     0.040   232.135
 ReadX        10098969     0.004    25.340
 LockX          20974     0.003     1.569
 UnlockX        20974     0.002     3.475
 Flush         451553    10.287   331.037

Throughput 1011.77 MB/sec  40 clients  40 procs  max_latency=331.045 ms

+10.8% throughput, -8.2% max latency

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2020-12-08 15:54:12 +01:00

480 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2007 Red Hat. All rights reserved.
*/
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/rwsem.h>
#include <linux/xattr.h>
#include <linux/security.h>
#include <linux/posix_acl_xattr.h>
#include <linux/iversion.h>
#include <linux/sched/mm.h>
#include "ctree.h"
#include "btrfs_inode.h"
#include "transaction.h"
#include "xattr.h"
#include "disk-io.h"
#include "props.h"
#include "locking.h"
int btrfs_getxattr(struct inode *inode, const char *name,
void *buffer, size_t size)
{
struct btrfs_dir_item *di;
struct btrfs_root *root = BTRFS_I(inode)->root;
struct btrfs_path *path;
struct extent_buffer *leaf;
int ret = 0;
unsigned long data_ptr;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
/* lookup the xattr by name */
di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(BTRFS_I(inode)),
name, strlen(name), 0);
if (!di) {
ret = -ENODATA;
goto out;
} else if (IS_ERR(di)) {
ret = PTR_ERR(di);
goto out;
}
leaf = path->nodes[0];
/* if size is 0, that means we want the size of the attr */
if (!size) {
ret = btrfs_dir_data_len(leaf, di);
goto out;
}
/* now get the data out of our dir_item */
if (btrfs_dir_data_len(leaf, di) > size) {
ret = -ERANGE;
goto out;
}
/*
* The way things are packed into the leaf is like this
* |struct btrfs_dir_item|name|data|
* where name is the xattr name, so security.foo, and data is the
* content of the xattr. data_ptr points to the location in memory
* where the data starts in the in memory leaf
*/
data_ptr = (unsigned long)((char *)(di + 1) +
btrfs_dir_name_len(leaf, di));
read_extent_buffer(leaf, buffer, data_ptr,
btrfs_dir_data_len(leaf, di));
ret = btrfs_dir_data_len(leaf, di);
out:
btrfs_free_path(path);
return ret;
}
int btrfs_setxattr(struct btrfs_trans_handle *trans, struct inode *inode,
const char *name, const void *value, size_t size, int flags)
{
struct btrfs_dir_item *di = NULL;
struct btrfs_root *root = BTRFS_I(inode)->root;
struct btrfs_fs_info *fs_info = root->fs_info;
struct btrfs_path *path;
size_t name_len = strlen(name);
int ret = 0;
ASSERT(trans);
if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
return -ENOSPC;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
path->skip_release_on_error = 1;
if (!value) {
di = btrfs_lookup_xattr(trans, root, path,
btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
if (!di && (flags & XATTR_REPLACE))
ret = -ENODATA;
else if (IS_ERR(di))
ret = PTR_ERR(di);
else if (di)
ret = btrfs_delete_one_dir_name(trans, root, path, di);
goto out;
}
/*
* For a replace we can't just do the insert blindly.
* Do a lookup first (read-only btrfs_search_slot), and return if xattr
* doesn't exist. If it exists, fall down below to the insert/replace
* path - we can't race with a concurrent xattr delete, because the VFS
* locks the inode's i_mutex before calling setxattr or removexattr.
*/
if (flags & XATTR_REPLACE) {
ASSERT(inode_is_locked(inode));
di = btrfs_lookup_xattr(NULL, root, path,
btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
if (!di)
ret = -ENODATA;
else if (IS_ERR(di))
ret = PTR_ERR(di);
if (ret)
goto out;
btrfs_release_path(path);
di = NULL;
}
ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
name, name_len, value, size);
if (ret == -EOVERFLOW) {
/*
* We have an existing item in a leaf, split_leaf couldn't
* expand it. That item might have or not a dir_item that
* matches our target xattr, so lets check.
*/
ret = 0;
btrfs_assert_tree_locked(path->nodes[0]);
di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
if (!di && !(flags & XATTR_REPLACE)) {
ret = -ENOSPC;
goto out;
}
} else if (ret == -EEXIST) {
ret = 0;
di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
ASSERT(di); /* logic error */
} else if (ret) {
goto out;
}
if (di && (flags & XATTR_CREATE)) {
ret = -EEXIST;
goto out;
}
if (di) {
/*
* We're doing a replace, and it must be atomic, that is, at
* any point in time we have either the old or the new xattr
* value in the tree. We don't want readers (getxattr and
* listxattrs) to miss a value, this is specially important
* for ACLs.
*/
const int slot = path->slots[0];
struct extent_buffer *leaf = path->nodes[0];
const u16 old_data_len = btrfs_dir_data_len(leaf, di);
const u32 item_size = btrfs_item_size_nr(leaf, slot);
const u32 data_size = sizeof(*di) + name_len + size;
struct btrfs_item *item;
unsigned long data_ptr;
char *ptr;
if (size > old_data_len) {
if (btrfs_leaf_free_space(leaf) <
(size - old_data_len)) {
ret = -ENOSPC;
goto out;
}
}
if (old_data_len + name_len + sizeof(*di) == item_size) {
/* No other xattrs packed in the same leaf item. */
if (size > old_data_len)
btrfs_extend_item(path, size - old_data_len);
else if (size < old_data_len)
btrfs_truncate_item(path, data_size, 1);
} else {
/* There are other xattrs packed in the same item. */
ret = btrfs_delete_one_dir_name(trans, root, path, di);
if (ret)
goto out;
btrfs_extend_item(path, data_size);
}
item = btrfs_item_nr(slot);
ptr = btrfs_item_ptr(leaf, slot, char);
ptr += btrfs_item_size(leaf, item) - data_size;
di = (struct btrfs_dir_item *)ptr;
btrfs_set_dir_data_len(leaf, di, size);
data_ptr = ((unsigned long)(di + 1)) + name_len;
write_extent_buffer(leaf, value, data_ptr, size);
btrfs_mark_buffer_dirty(leaf);
} else {
/*
* Insert, and we had space for the xattr, so path->slots[0] is
* where our xattr dir_item is and btrfs_insert_xattr_item()
* filled it.
*/
}
out:
btrfs_free_path(path);
if (!ret) {
set_bit(BTRFS_INODE_COPY_EVERYTHING,
&BTRFS_I(inode)->runtime_flags);
clear_bit(BTRFS_INODE_NO_XATTRS, &BTRFS_I(inode)->runtime_flags);
}
return ret;
}
/*
* @value: "" makes the attribute to empty, NULL removes it
*/
int btrfs_setxattr_trans(struct inode *inode, const char *name,
const void *value, size_t size, int flags)
{
struct btrfs_root *root = BTRFS_I(inode)->root;
struct btrfs_trans_handle *trans;
int ret;
trans = btrfs_start_transaction(root, 2);
if (IS_ERR(trans))
return PTR_ERR(trans);
ret = btrfs_setxattr(trans, inode, name, value, size, flags);
if (ret)
goto out;
inode_inc_iversion(inode);
inode->i_ctime = current_time(inode);
ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
BUG_ON(ret);
out:
btrfs_end_transaction(trans);
return ret;
}
ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
{
struct btrfs_key key;
struct inode *inode = d_inode(dentry);
struct btrfs_root *root = BTRFS_I(inode)->root;
struct btrfs_path *path;
int ret = 0;
size_t total_size = 0, size_left = size;
/*
* ok we want all objects associated with this id.
* NOTE: we set key.offset = 0; because we want to start with the
* first xattr that we find and walk forward
*/
key.objectid = btrfs_ino(BTRFS_I(inode));
key.type = BTRFS_XATTR_ITEM_KEY;
key.offset = 0;
path = btrfs_alloc_path();
if (!path)
return -ENOMEM;
path->reada = READA_FORWARD;
/* search for our xattrs */
ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
if (ret < 0)
goto err;
while (1) {
struct extent_buffer *leaf;
int slot;
struct btrfs_dir_item *di;
struct btrfs_key found_key;
u32 item_size;
u32 cur;
leaf = path->nodes[0];
slot = path->slots[0];
/* this is where we start walking through the path */
if (slot >= btrfs_header_nritems(leaf)) {
/*
* if we've reached the last slot in this leaf we need
* to go to the next leaf and reset everything
*/
ret = btrfs_next_leaf(root, path);
if (ret < 0)
goto err;
else if (ret > 0)
break;
continue;
}
btrfs_item_key_to_cpu(leaf, &found_key, slot);
/* check to make sure this item is what we want */
if (found_key.objectid != key.objectid)
break;
if (found_key.type > BTRFS_XATTR_ITEM_KEY)
break;
if (found_key.type < BTRFS_XATTR_ITEM_KEY)
goto next_item;
di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
item_size = btrfs_item_size_nr(leaf, slot);
cur = 0;
while (cur < item_size) {
u16 name_len = btrfs_dir_name_len(leaf, di);
u16 data_len = btrfs_dir_data_len(leaf, di);
u32 this_len = sizeof(*di) + name_len + data_len;
unsigned long name_ptr = (unsigned long)(di + 1);
total_size += name_len + 1;
/*
* We are just looking for how big our buffer needs to
* be.
*/
if (!size)
goto next;
if (!buffer || (name_len + 1) > size_left) {
ret = -ERANGE;
goto err;
}
read_extent_buffer(leaf, buffer, name_ptr, name_len);
buffer[name_len] = '\0';
size_left -= name_len + 1;
buffer += name_len + 1;
next:
cur += this_len;
di = (struct btrfs_dir_item *)((char *)di + this_len);
}
next_item:
path->slots[0]++;
}
ret = total_size;
err:
btrfs_free_path(path);
return ret;
}
static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
struct dentry *unused, struct inode *inode,
const char *name, void *buffer, size_t size)
{
name = xattr_full_name(handler, name);
return btrfs_getxattr(inode, name, buffer, size);
}
static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
struct dentry *unused, struct inode *inode,
const char *name, const void *buffer,
size_t size, int flags)
{
name = xattr_full_name(handler, name);
return btrfs_setxattr_trans(inode, name, buffer, size, flags);
}
static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
struct dentry *unused, struct inode *inode,
const char *name, const void *value,
size_t size, int flags)
{
int ret;
struct btrfs_trans_handle *trans;
struct btrfs_root *root = BTRFS_I(inode)->root;
name = xattr_full_name(handler, name);
ret = btrfs_validate_prop(name, value, size);
if (ret)
return ret;
trans = btrfs_start_transaction(root, 2);
if (IS_ERR(trans))
return PTR_ERR(trans);
ret = btrfs_set_prop(trans, inode, name, value, size, flags);
if (!ret) {
inode_inc_iversion(inode);
inode->i_ctime = current_time(inode);
ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
BUG_ON(ret);
}
btrfs_end_transaction(trans);
return ret;
}
static const struct xattr_handler btrfs_security_xattr_handler = {
.prefix = XATTR_SECURITY_PREFIX,
.get = btrfs_xattr_handler_get,
.set = btrfs_xattr_handler_set,
};
static const struct xattr_handler btrfs_trusted_xattr_handler = {
.prefix = XATTR_TRUSTED_PREFIX,
.get = btrfs_xattr_handler_get,
.set = btrfs_xattr_handler_set,
};
static const struct xattr_handler btrfs_user_xattr_handler = {
.prefix = XATTR_USER_PREFIX,
.get = btrfs_xattr_handler_get,
.set = btrfs_xattr_handler_set,
};
static const struct xattr_handler btrfs_btrfs_xattr_handler = {
.prefix = XATTR_BTRFS_PREFIX,
.get = btrfs_xattr_handler_get,
.set = btrfs_xattr_handler_set_prop,
};
const struct xattr_handler *btrfs_xattr_handlers[] = {
&btrfs_security_xattr_handler,
#ifdef CONFIG_BTRFS_FS_POSIX_ACL
&posix_acl_access_xattr_handler,
&posix_acl_default_xattr_handler,
#endif
&btrfs_trusted_xattr_handler,
&btrfs_user_xattr_handler,
&btrfs_btrfs_xattr_handler,
NULL,
};
static int btrfs_initxattrs(struct inode *inode,
const struct xattr *xattr_array, void *fs_private)
{
struct btrfs_trans_handle *trans = fs_private;
const struct xattr *xattr;
unsigned int nofs_flag;
char *name;
int err = 0;
/*
* We're holding a transaction handle, so use a NOFS memory allocation
* context to avoid deadlock if reclaim happens.
*/
nofs_flag = memalloc_nofs_save();
for (xattr = xattr_array; xattr->name != NULL; xattr++) {
name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
strlen(xattr->name) + 1, GFP_KERNEL);
if (!name) {
err = -ENOMEM;
break;
}
strcpy(name, XATTR_SECURITY_PREFIX);
strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
err = btrfs_setxattr(trans, inode, name, xattr->value,
xattr->value_len, 0);
kfree(name);
if (err < 0)
break;
}
memalloc_nofs_restore(nofs_flag);
return err;
}
int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
struct inode *inode, struct inode *dir,
const struct qstr *qstr)
{
return security_inode_init_security(inode, dir, qstr,
&btrfs_initxattrs, trans);
}