linux-stable/fs/afs/xdr_fs.h
David Howells 366911cd76 afs: Fix directory entry size calculation
The number of dirent records used by an AFS directory entry should be
calculated using the assumption that there is a 16-byte name field in the
first block, rather than a 20-byte name field (which is actually the case).
This miscalculation is historic and effectively standard, so we have to use
it.

The calculation we need to use is:

	1 + (((strlen(name) + 1) + 15) >> 5)

where we are adding one to the strlen() result to account for the NUL
termination.

Fix this by the following means:

 (1) Create an inline function to do the calculation for a given name
     length.

 (2) Use the function to calculate the number of records used for a dirent
     in afs_dir_iterate_block().

     Use this to move the over-end check out of the loop since it only
     needs to be done once.

     Further use this to only go through the loop for the 2nd+ records
     composing an entry.  The only test there now is for if the record is
     allocated - and we already checked the first block at the top of the
     outer loop.

 (3) Add a max name length check in afs_dir_iterate_block().

 (4) Make afs_edit_dir_add() and afs_edit_dir_remove() use the function
     from (1) to calculate the number of blocks rather than doing it
     incorrectly themselves.

Fixes: 63a4681ff3 ("afs: Locally edit directory data for mkdir/create/unlink/...")
Fixes: ^1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Marc Dionne <marc.dionne@auristor.com>
2021-01-04 12:25:19 +00:00

116 lines
2.7 KiB
C

/* SPDX-License-Identifier: GPL-2.0-or-later */
/* AFS fileserver XDR types
*
* Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#ifndef XDR_FS_H
#define XDR_FS_H
struct afs_xdr_AFSFetchStatus {
__be32 if_version;
#define AFS_FSTATUS_VERSION 1
__be32 type;
__be32 nlink;
__be32 size_lo;
__be32 data_version_lo;
__be32 author;
__be32 owner;
__be32 caller_access;
__be32 anon_access;
__be32 mode;
__be32 parent_vnode;
__be32 parent_unique;
__be32 seg_size;
__be32 mtime_client;
__be32 mtime_server;
__be32 group;
__be32 sync_counter;
__be32 data_version_hi;
__be32 lock_count;
__be32 size_hi;
__be32 abort_code;
} __packed;
#define AFS_DIR_HASHTBL_SIZE 128
#define AFS_DIR_DIRENT_SIZE 32
#define AFS_DIR_SLOTS_PER_BLOCK 64
#define AFS_DIR_BLOCK_SIZE 2048
#define AFS_DIR_BLOCKS_PER_PAGE (PAGE_SIZE / AFS_DIR_BLOCK_SIZE)
#define AFS_DIR_MAX_SLOTS 65536
#define AFS_DIR_BLOCKS_WITH_CTR 128
#define AFS_DIR_MAX_BLOCKS 1023
#define AFS_DIR_RESV_BLOCKS 1
#define AFS_DIR_RESV_BLOCKS0 13
/*
* Directory entry structure.
*/
union afs_xdr_dirent {
struct {
u8 valid;
u8 unused[1];
__be16 hash_next;
__be32 vnode;
__be32 unique;
u8 name[];
/* When determining the number of dirent slots needed to
* represent a directory entry, name should be assumed to be 16
* bytes, due to a now-standardised (mis)calculation, but it is
* in fact 20 bytes in size. afs_dir_calc_slots() should be
* used for this.
*
* For names longer than (16 or) 20 bytes, extra slots should
* be annexed to this one using the extended_name format.
*/
} u;
u8 extended_name[32];
} __packed;
/*
* Directory block header (one at the beginning of every 2048-byte block).
*/
struct afs_xdr_dir_hdr {
__be16 npages;
__be16 magic;
#define AFS_DIR_MAGIC htons(1234)
u8 reserved;
u8 bitmap[8];
u8 pad[19];
} __packed;
/*
* Directory block layout
*/
union afs_xdr_dir_block {
struct afs_xdr_dir_hdr hdr;
struct {
struct afs_xdr_dir_hdr hdr;
u8 alloc_ctrs[AFS_DIR_MAX_BLOCKS];
__be16 hashtable[AFS_DIR_HASHTBL_SIZE];
} meta;
union afs_xdr_dirent dirents[AFS_DIR_SLOTS_PER_BLOCK];
} __packed;
/*
* Directory layout on a linux VM page.
*/
struct afs_xdr_dir_page {
union afs_xdr_dir_block blocks[AFS_DIR_BLOCKS_PER_PAGE];
};
/*
* Calculate the number of dirent slots required for any given name length.
* The calculation is made assuming the part of the name in the first slot is
* 16 bytes, rather than 20, but this miscalculation is now standardised.
*/
static inline unsigned int afs_dir_calc_slots(size_t name_len)
{
name_len++; /* NUL-terminated */
return 1 + ((name_len + 15) / AFS_DIR_DIRENT_SIZE);
}
#endif /* XDR_FS_H */