![Tahsin Erdogan](/assets/img/avatar_default.png)
Ext4 now supports xattr values that are up to 64k in size (vfs limit). Large xattr values are stored in external inodes each one holding a single value. Once written the data blocks of these inodes are immutable. The real world use cases are expected to have a lot of value duplication such as inherited acls etc. To reduce data duplication on disk, this patch implements a deduplicator that allows sharing of xattr inodes. The deduplication is based on an in-memory hash lookup that is a best effort sharing scheme. When a xattr inode is read from disk (i.e. getxattr() call), its crc32c hash is added to a hash table. Before creating a new xattr inode for a value being set, the hash table is checked to see if an existing inode holds an identical value. If such an inode is found, the ref count on that inode is incremented. On value removal the ref count is decremented and if it reaches zero the inode is deleted. The quota charging for such inodes is manually managed. Every reference holder is charged the full size as if there was no sharing happening. This is consistent with how xattr blocks are also charged. [ Fixed up journal credits calculation to handle inline data and the rare case where an shared xattr block can get freed when two thread race on breaking the xattr block sharing. --tytso ] Signed-off-by: Tahsin Erdogan <tahsin@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
285 lines
6.2 KiB
C
285 lines
6.2 KiB
C
/*
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* linux/fs/ext4/acl.c
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*
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* Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
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*/
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#include <linux/quotaops.h>
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#include "ext4_jbd2.h"
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#include "ext4.h"
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#include "xattr.h"
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#include "acl.h"
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/*
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* Convert from filesystem to in-memory representation.
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*/
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static struct posix_acl *
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ext4_acl_from_disk(const void *value, size_t size)
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{
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const char *end = (char *)value + size;
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int n, count;
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struct posix_acl *acl;
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if (!value)
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return NULL;
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if (size < sizeof(ext4_acl_header))
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return ERR_PTR(-EINVAL);
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if (((ext4_acl_header *)value)->a_version !=
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cpu_to_le32(EXT4_ACL_VERSION))
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return ERR_PTR(-EINVAL);
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value = (char *)value + sizeof(ext4_acl_header);
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count = ext4_acl_count(size);
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if (count < 0)
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return ERR_PTR(-EINVAL);
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if (count == 0)
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return NULL;
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acl = posix_acl_alloc(count, GFP_NOFS);
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if (!acl)
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return ERR_PTR(-ENOMEM);
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for (n = 0; n < count; n++) {
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ext4_acl_entry *entry =
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(ext4_acl_entry *)value;
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if ((char *)value + sizeof(ext4_acl_entry_short) > end)
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goto fail;
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acl->a_entries[n].e_tag = le16_to_cpu(entry->e_tag);
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acl->a_entries[n].e_perm = le16_to_cpu(entry->e_perm);
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switch (acl->a_entries[n].e_tag) {
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case ACL_USER_OBJ:
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case ACL_GROUP_OBJ:
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case ACL_MASK:
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case ACL_OTHER:
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value = (char *)value +
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sizeof(ext4_acl_entry_short);
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break;
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case ACL_USER:
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value = (char *)value + sizeof(ext4_acl_entry);
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if ((char *)value > end)
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goto fail;
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acl->a_entries[n].e_uid =
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make_kuid(&init_user_ns,
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le32_to_cpu(entry->e_id));
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break;
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case ACL_GROUP:
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value = (char *)value + sizeof(ext4_acl_entry);
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if ((char *)value > end)
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goto fail;
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acl->a_entries[n].e_gid =
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make_kgid(&init_user_ns,
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le32_to_cpu(entry->e_id));
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break;
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default:
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goto fail;
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}
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}
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if (value != end)
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goto fail;
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return acl;
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fail:
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posix_acl_release(acl);
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return ERR_PTR(-EINVAL);
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}
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/*
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* Convert from in-memory to filesystem representation.
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*/
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static void *
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ext4_acl_to_disk(const struct posix_acl *acl, size_t *size)
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{
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ext4_acl_header *ext_acl;
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char *e;
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size_t n;
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*size = ext4_acl_size(acl->a_count);
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ext_acl = kmalloc(sizeof(ext4_acl_header) + acl->a_count *
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sizeof(ext4_acl_entry), GFP_NOFS);
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if (!ext_acl)
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return ERR_PTR(-ENOMEM);
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ext_acl->a_version = cpu_to_le32(EXT4_ACL_VERSION);
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e = (char *)ext_acl + sizeof(ext4_acl_header);
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for (n = 0; n < acl->a_count; n++) {
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const struct posix_acl_entry *acl_e = &acl->a_entries[n];
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ext4_acl_entry *entry = (ext4_acl_entry *)e;
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entry->e_tag = cpu_to_le16(acl_e->e_tag);
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entry->e_perm = cpu_to_le16(acl_e->e_perm);
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switch (acl_e->e_tag) {
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case ACL_USER:
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entry->e_id = cpu_to_le32(
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from_kuid(&init_user_ns, acl_e->e_uid));
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e += sizeof(ext4_acl_entry);
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break;
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case ACL_GROUP:
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entry->e_id = cpu_to_le32(
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from_kgid(&init_user_ns, acl_e->e_gid));
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e += sizeof(ext4_acl_entry);
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break;
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case ACL_USER_OBJ:
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case ACL_GROUP_OBJ:
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case ACL_MASK:
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case ACL_OTHER:
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e += sizeof(ext4_acl_entry_short);
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break;
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default:
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goto fail;
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}
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}
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return (char *)ext_acl;
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fail:
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kfree(ext_acl);
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return ERR_PTR(-EINVAL);
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}
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/*
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* Inode operation get_posix_acl().
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*
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* inode->i_mutex: don't care
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*/
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struct posix_acl *
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ext4_get_acl(struct inode *inode, int type)
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{
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int name_index;
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char *value = NULL;
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struct posix_acl *acl;
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int retval;
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switch (type) {
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case ACL_TYPE_ACCESS:
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name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
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break;
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case ACL_TYPE_DEFAULT:
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name_index = EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT;
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break;
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default:
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BUG();
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}
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retval = ext4_xattr_get(inode, name_index, "", NULL, 0);
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if (retval > 0) {
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value = kmalloc(retval, GFP_NOFS);
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if (!value)
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return ERR_PTR(-ENOMEM);
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retval = ext4_xattr_get(inode, name_index, "", value, retval);
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}
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if (retval > 0)
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acl = ext4_acl_from_disk(value, retval);
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else if (retval == -ENODATA || retval == -ENOSYS)
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acl = NULL;
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else
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acl = ERR_PTR(retval);
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kfree(value);
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return acl;
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}
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/*
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* Set the access or default ACL of an inode.
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*
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* inode->i_mutex: down unless called from ext4_new_inode
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*/
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static int
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__ext4_set_acl(handle_t *handle, struct inode *inode, int type,
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struct posix_acl *acl)
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{
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int name_index;
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void *value = NULL;
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size_t size = 0;
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int error;
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switch (type) {
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case ACL_TYPE_ACCESS:
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name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
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if (acl) {
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error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
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if (error)
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return error;
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inode->i_ctime = current_time(inode);
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ext4_mark_inode_dirty(handle, inode);
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}
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break;
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case ACL_TYPE_DEFAULT:
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name_index = EXT4_XATTR_INDEX_POSIX_ACL_DEFAULT;
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if (!S_ISDIR(inode->i_mode))
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return acl ? -EACCES : 0;
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break;
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default:
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return -EINVAL;
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}
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if (acl) {
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value = ext4_acl_to_disk(acl, &size);
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if (IS_ERR(value))
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return (int)PTR_ERR(value);
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}
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error = ext4_xattr_set_handle(handle, inode, name_index, "",
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value, size, 0);
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kfree(value);
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if (!error)
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set_cached_acl(inode, type, acl);
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return error;
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}
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int
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ext4_set_acl(struct inode *inode, struct posix_acl *acl, int type)
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{
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handle_t *handle;
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int error, credits, retries = 0;
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size_t acl_size = acl ? ext4_acl_size(acl->a_count) : 0;
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error = dquot_initialize(inode);
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if (error)
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return error;
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retry:
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error = ext4_xattr_set_credits(inode, acl_size, &credits);
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if (error)
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return error;
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handle = ext4_journal_start(inode, EXT4_HT_XATTR, credits);
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if (IS_ERR(handle))
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return PTR_ERR(handle);
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error = __ext4_set_acl(handle, inode, type, acl);
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ext4_journal_stop(handle);
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if (error == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
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goto retry;
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return error;
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}
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/*
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* Initialize the ACLs of a new inode. Called from ext4_new_inode.
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*
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* dir->i_mutex: down
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* inode->i_mutex: up (access to inode is still exclusive)
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*/
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int
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ext4_init_acl(handle_t *handle, struct inode *inode, struct inode *dir)
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{
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struct posix_acl *default_acl, *acl;
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int error;
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error = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
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if (error)
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return error;
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if (default_acl) {
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error = __ext4_set_acl(handle, inode, ACL_TYPE_DEFAULT,
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default_acl);
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posix_acl_release(default_acl);
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}
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if (acl) {
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if (!error)
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error = __ext4_set_acl(handle, inode, ACL_TYPE_ACCESS,
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acl);
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posix_acl_release(acl);
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}
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return error;
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}
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