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linux: Add buffer_head.h and journal-head.h stubs

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Add stub headers for buffer head management:

- buffer_head.h: buffer head structure and state management
  functions (bh_*_bit helpers, BUFFER_FNS/TAS_BUFFER_FNS macros)
- journal-head.h: journal buffer head structure for jbd2

These provide minimal interfaces needed for ext4l filesystem
compilation in U-Boot.

Co-developed-by: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: Simon Glass <simon.glass@canonical.com>
This commit is contained in:
Simon Glass
2025-12-17 13:52:21 -07:00
parent 4c245023bb
commit 6f87163eda
2 changed files with 301 additions and 0 deletions
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187
include/linux/buffer_head.h Normal file
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/* SPDX-License-Identifier: GPL-2.0 */
/*
* include/linux/buffer_head.h
*
* Everything to do with buffer_heads.
* Minimal version for U-Boot ext4l - based on Linux 6.18
*/
#ifndef _LINUX_BUFFER_HEAD_H
#define _LINUX_BUFFER_HEAD_H
#include <linux/types.h>
#include <linux/list.h>
#include <linux/spinlock.h>
/* Simple atomic_inc/dec for U-Boot (single-threaded) */
#ifndef atomic_inc
#define atomic_inc(v) ((v)->counter++)
#endif
#ifndef atomic_dec
#define atomic_dec(v) ((v)->counter--)
#endif
enum bh_state_bits {
BH_Uptodate, /* Contains valid data */
BH_Dirty, /* Is dirty */
BH_Lock, /* Is locked */
BH_Req, /* Has been submitted for I/O */
BH_Mapped, /* Has a disk mapping */
BH_New, /* Disk mapping was newly created by get_block */
BH_Async_Read, /* Is under end_buffer_async_read I/O */
BH_Async_Write, /* Is under end_buffer_async_write I/O */
BH_Delay, /* Buffer is not yet allocated on disk */
BH_Boundary, /* Block is followed by a discontiguity */
BH_Write_EIO, /* I/O error on write */
BH_Unwritten, /* Buffer is allocated on disk but not written */
BH_Quiet, /* Buffer Error Prinks to be quiet */
BH_Meta, /* Buffer contains metadata */
BH_Prio, /* Buffer should be submitted with REQ_PRIO */
BH_Defer_Completion, /* Defer AIO completion to workqueue */
BH_Migrate, /* Buffer is being migrated (norefs) */
BH_PrivateStart,/* not a state bit, but the first bit available
* for private allocation by other entities
*/
};
#define MAX_BUF_PER_PAGE (PAGE_SIZE / 512)
struct page;
struct folio;
struct buffer_head;
struct address_space;
struct block_device;
typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
/*
* Historically, a buffer_head was used to map a single block
* within a page, and of course as the unit of I/O through the
* filesystem and block layers. Nowadays the basic I/O unit
* is the bio, and buffer_heads are used for extracting block
* mappings (via a get_block_t call), for tracking state within
* a folio (via a folio_mapping) and for wrapping bio submission
* for backward compatibility reasons (e.g. submit_bh).
*/
struct buffer_head {
unsigned long b_state; /* buffer state bitmap (see above) */
struct buffer_head *b_this_page;/* circular list of page's buffers */
union {
struct page *b_page; /* the page this bh is mapped to */
struct folio *b_folio; /* the folio this bh is mapped to */
};
sector_t b_blocknr; /* start block number */
size_t b_size; /* size of mapping */
char *b_data; /* pointer to data within the page */
struct block_device *b_bdev;
bh_end_io_t *b_end_io; /* I/O completion */
void *b_private; /* reserved for b_end_io */
struct list_head b_assoc_buffers; /* associated with another mapping */
struct address_space *b_assoc_map; /* mapping this buffer is
associated with */
atomic_t b_count; /* users using this buffer_head */
spinlock_t b_uptodate_lock; /* Used by the first bh in a page, to
* serialise IO completion of other
* buffers in the page */
};
/*
* Buffer head bit operations - inline implementations.
* These don't use the extern set_bit/clear_bit from asm/bitops.h
* since sandbox doesn't implement them.
*/
static inline void bh_set_bit(int nr, unsigned long *addr)
{
*addr |= (1UL << nr);
}
static inline void bh_clear_bit(int nr, unsigned long *addr)
{
*addr &= ~(1UL << nr);
}
static inline int bh_test_bit(int nr, const unsigned long *addr)
{
return (*addr >> nr) & 1;
}
static inline int bh_test_and_set_bit(int nr, unsigned long *addr)
{
int old = (*addr >> nr) & 1;
*addr |= (1UL << nr);
return old;
}
static inline int bh_test_and_clear_bit(int nr, unsigned long *addr)
{
int old = (*addr >> nr) & 1;
*addr &= ~(1UL << nr);
return old;
}
/*
* macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
* and buffer_foo() functions.
*/
#define BUFFER_FNS(bit, name) \
static __always_inline void set_buffer_##name(struct buffer_head *bh) \
{ \
if (!bh_test_bit(BH_##bit, &(bh)->b_state)) \
bh_set_bit(BH_##bit, &(bh)->b_state); \
} \
static __always_inline void clear_buffer_##name(struct buffer_head *bh) \
{ \
bh_clear_bit(BH_##bit, &(bh)->b_state); \
} \
static __always_inline int buffer_##name(const struct buffer_head *bh) \
{ \
return bh_test_bit(BH_##bit, &(bh)->b_state); \
}
/*
* test_set_buffer_foo() and test_clear_buffer_foo()
*/
#define TAS_BUFFER_FNS(bit, name) \
static __always_inline int test_set_buffer_##name(struct buffer_head *bh) \
{ \
return bh_test_and_set_bit(BH_##bit, &(bh)->b_state); \
} \
static __always_inline int test_clear_buffer_##name(struct buffer_head *bh) \
{ \
return bh_test_and_clear_bit(BH_##bit, &(bh)->b_state); \
}
BUFFER_FNS(Uptodate, uptodate)
BUFFER_FNS(Dirty, dirty)
BUFFER_FNS(Lock, locked)
BUFFER_FNS(Req, req)
BUFFER_FNS(Mapped, mapped)
BUFFER_FNS(New, new)
BUFFER_FNS(Async_Read, async_read)
BUFFER_FNS(Async_Write, async_write)
BUFFER_FNS(Delay, delay)
BUFFER_FNS(Boundary, boundary)
BUFFER_FNS(Write_EIO, write_io_error)
BUFFER_FNS(Unwritten, unwritten)
BUFFER_FNS(Meta, meta)
BUFFER_FNS(Prio, prio)
BUFFER_FNS(Defer_Completion, defer_completion)
static inline void get_bh(struct buffer_head *bh)
{
atomic_inc(&bh->b_count);
}
static inline void put_bh(struct buffer_head *bh)
{
atomic_dec(&bh->b_count);
}
/* Stubs for U-Boot */
#define brelse(bh) do { if (bh) put_bh(bh); } while (0)
#define __brelse(bh) do { put_bh(bh); } while (0)
#endif /* _LINUX_BUFFER_HEAD_H */

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include/linux/journal-head.h Normal file
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/* SPDX-License-Identifier: GPL-2.0 */
/*
* include/linux/journal-head.h
*
* buffer_head fields for JBD
*
* 27 May 2001 Andrew Morton
* Created - pulled out of fs.h
*/
#ifndef JOURNAL_HEAD_H_INCLUDED
#define JOURNAL_HEAD_H_INCLUDED
#include <linux/spinlock.h>
typedef unsigned int tid_t; /* Unique transaction ID */
typedef struct transaction_s transaction_t; /* Compound transaction type */
struct buffer_head;
struct journal_head {
/*
* Points back to our buffer_head. [jbd_lock_bh_journal_head()]
*/
struct buffer_head *b_bh;
/*
* Protect the buffer head state
*/
spinlock_t b_state_lock;
/*
* Reference count - see description in journal.c
* [jbd_lock_bh_journal_head()]
*/
int b_jcount;
/*
* Journalling list for this buffer [b_state_lock]
* NOTE: We *cannot* combine this with b_modified into a bitfield
* as gcc would then (which the C standard allows but which is
* very unuseful) make 64-bit accesses to the bitfield and clobber
* b_jcount if its update races with bitfield modification.
*/
unsigned b_jlist;
/*
* This flag signals the buffer has been modified by
* the currently running transaction
* [b_state_lock]
*/
unsigned b_modified;
/*
* Copy of the buffer data frozen for writing to the log.
* [b_state_lock]
*/
char *b_frozen_data;
/*
* Pointer to a saved copy of the buffer containing no uncommitted
* deallocation references, so that allocations can avoid overwriting
* uncommitted deletes. [b_state_lock]
*/
char *b_committed_data;
/*
* Pointer to the compound transaction which owns this buffer's
* metadata: either the running transaction or the committing
* transaction (if there is one). Only applies to buffers on a
* transaction's data or metadata journaling list.
* [j_list_lock] [b_state_lock]
* Either of these locks is enough for reading, both are needed for
* changes.
*/
transaction_t *b_transaction;
/*
* Pointer to the running compound transaction which is currently
* modifying the buffer's metadata, if there was already a transaction
* committing it when the new transaction touched it.
* [t_list_lock] [b_state_lock]
*/
transaction_t *b_next_transaction;
/*
* Doubly-linked list of buffers on a transaction's data, metadata or
* forget queue. [t_list_lock] [b_state_lock]
*/
struct journal_head *b_tnext, *b_tprev;
/*
* Pointer to the compound transaction against which this buffer
* is checkpointed. Only dirty buffers can be checkpointed.
* [j_list_lock]
*/
transaction_t *b_cp_transaction;
/*
* Doubly-linked list of buffers still remaining to be flushed
* before an old transaction can be checkpointed.
* [j_list_lock]
*/
struct journal_head *b_cpnext, *b_cpprev;
/* Trigger type */
struct jbd2_buffer_trigger_type *b_triggers;
/* Trigger type for the committing transaction's frozen data */
struct jbd2_buffer_trigger_type *b_frozen_triggers;
};
#endif /* JOURNAL_HEAD_H_INCLUDED */