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[PATCH] BLOCK: Make it possible to disable the block layer [try #6]

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Make it possible to disable the block layer.  Not all embedded devices require
it, some can make do with just JFFS2, NFS, ramfs, etc - none of which require
the block layer to be present.

This patch does the following:

 (*) Introduces CONFIG_BLOCK to disable the block layer, buffering and blockdev
     support.

 (*) Adds dependencies on CONFIG_BLOCK to any configuration item that controls
     an item that uses the block layer.  This includes:

     (*) Block I/O tracing.

     (*) Disk partition code.

     (*) All filesystems that are block based, eg: Ext3, ReiserFS, ISOFS.

     (*) The SCSI layer.  As far as I can tell, even SCSI chardevs use the
     	 block layer to do scheduling.  Some drivers that use SCSI facilities -
     	 such as USB storage - end up disabled indirectly from this.

     (*) Various block-based device drivers, such as IDE and the old CDROM
     	 drivers.

     (*) MTD blockdev handling and FTL.

     (*) JFFS - which uses set_bdev_super(), something it could avoid doing by
     	 taking a leaf out of JFFS2's book.

 (*) Makes most of the contents of linux/blkdev.h, linux/buffer_head.h and
     linux/elevator.h contingent on CONFIG_BLOCK being set.  sector_div() is,
     however, still used in places, and so is still available.

 (*) Also made contingent are the contents of linux/mpage.h, linux/genhd.h and
     parts of linux/fs.h.

 (*) Makes a number of files in fs/ contingent on CONFIG_BLOCK.

 (*) Makes mm/bounce.c (bounce buffering) contingent on CONFIG_BLOCK.

 (*) set_page_dirty() doesn't call __set_page_dirty_buffers() if CONFIG_BLOCK
     is not enabled.

 (*) fs/no-block.c is created to hold out-of-line stubs and things that are
     required when CONFIG_BLOCK is not set:

     (*) Default blockdev file operations (to give error ENODEV on opening).

 (*) Makes some /proc changes:

     (*) /proc/devices does not list any blockdevs.

     (*) /proc/diskstats and /proc/partitions are contingent on CONFIG_BLOCK.

 (*) Makes some compat ioctl handling contingent on CONFIG_BLOCK.

 (*) If CONFIG_BLOCK is not defined, makes sys_quotactl() return -ENODEV if
     given command other than Q_SYNC or if a special device is specified.

 (*) In init/do_mounts.c, no reference is made to the blockdev routines if
     CONFIG_BLOCK is not defined.  This does not prohibit NFS roots or JFFS2.

 (*) The bdflush, ioprio_set and ioprio_get syscalls can now be absent (return
     error ENOSYS by way of cond_syscall if so).

 (*) The seclvl_bd_claim() and seclvl_bd_release() security calls do nothing if
     CONFIG_BLOCK is not set, since they can't then happen.

Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
David Howells
2006-09-30 20:45:40 +02:00
committed by Jens Axboe
parent d366e40a1c
commit 9361401eb7
44 changed files with 308 additions and 63 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
include/linux/fs.h
View File

@ -1482,6 +1482,7 @@ extern void __init vfs_caches_init(unsigned long);
extern void putname(const char *name);
#endif
#ifdef CONFIG_BLOCK
extern int register_blkdev(unsigned int, const char *);
extern int unregister_blkdev(unsigned int, const char *);
extern struct block_device *bdget(dev_t);
@ -1490,11 +1491,15 @@ extern void bd_forget(struct inode *inode);
extern void bdput(struct block_device *);
extern struct block_device *open_by_devnum(dev_t, unsigned);
extern struct block_device *open_partition_by_devnum(dev_t, unsigned);
extern const struct file_operations def_blk_fops;
extern const struct address_space_operations def_blk_aops;
#else
static inline void bd_forget(struct inode *inode) {}
#endif
extern const struct file_operations def_blk_fops;
extern const struct file_operations def_chr_fops;
extern const struct file_operations bad_sock_fops;
extern const struct file_operations def_fifo_fops;
#ifdef CONFIG_BLOCK
extern int ioctl_by_bdev(struct block_device *, unsigned, unsigned long);
extern int blkdev_ioctl(struct inode *, struct file *, unsigned, unsigned long);
extern long compat_blkdev_ioctl(struct file *, unsigned, unsigned long);
@ -1510,6 +1515,7 @@ extern void bd_release_from_disk(struct block_device *, struct gendisk *);
#define bd_claim_by_disk(bdev, holder, disk) bd_claim(bdev, holder)
#define bd_release_from_disk(bdev, disk) bd_release(bdev)
#endif
#endif
/* fs/char_dev.c */
#define CHRDEV_MAJOR_HASH_SIZE 255
@ -1523,14 +1529,19 @@ extern int chrdev_open(struct inode *, struct file *);
extern void chrdev_show(struct seq_file *,off_t);
/* fs/block_dev.c */
#define BLKDEV_MAJOR_HASH_SIZE 255
#define BDEVNAME_SIZE 32 /* Largest string for a blockdev identifier */
#ifdef CONFIG_BLOCK
#define BLKDEV_MAJOR_HASH_SIZE 255
extern const char *__bdevname(dev_t, char *buffer);
extern const char *bdevname(struct block_device *bdev, char *buffer);
extern struct block_device *lookup_bdev(const char *);
extern struct block_device *open_bdev_excl(const char *, int, void *);
extern void close_bdev_excl(struct block_device *);
extern void blkdev_show(struct seq_file *,off_t);
#else
#define BLKDEV_MAJOR_HASH_SIZE 0
#endif
extern void init_special_inode(struct inode *, umode_t, dev_t);
@ -1544,6 +1555,7 @@ extern const struct file_operations rdwr_fifo_fops;
extern int fs_may_remount_ro(struct super_block *);
#ifdef CONFIG_BLOCK
/*
* return READ, READA, or WRITE
*/
@ -1555,9 +1567,10 @@ extern int fs_may_remount_ro(struct super_block *);
#define bio_data_dir(bio) ((bio)->bi_rw & 1)
extern int check_disk_change(struct block_device *);
extern int invalidate_inodes(struct super_block *);
extern int __invalidate_device(struct block_device *);
extern int invalidate_partition(struct gendisk *, int);
#endif
extern int invalidate_inodes(struct super_block *);
unsigned long invalidate_mapping_pages(struct address_space *mapping,
pgoff_t start, pgoff_t end);
unsigned long invalidate_inode_pages(struct address_space *mapping);
@ -1590,7 +1603,9 @@ extern void emergency_sync(void);
extern void emergency_remount(void);
extern int do_remount_sb(struct super_block *sb, int flags,
void *data, int force);
#ifdef CONFIG_BLOCK
extern sector_t bmap(struct inode *, sector_t);
#endif
extern int notify_change(struct dentry *, struct iattr *);
extern int permission(struct inode *, int, struct nameidata *);
extern int generic_permission(struct inode *, int,
@ -1673,9 +1688,11 @@ static inline void insert_inode_hash(struct inode *inode) {
extern struct file * get_empty_filp(void);
extern void file_move(struct file *f, struct list_head *list);
extern void file_kill(struct file *f);
#ifdef CONFIG_BLOCK
struct bio;
extern void submit_bio(int, struct bio *);
extern int bdev_read_only(struct block_device *);
#endif
extern int set_blocksize(struct block_device *, int);
extern int sb_set_blocksize(struct super_block *, int);
extern int sb_min_blocksize(struct super_block *, int);
@ -1756,6 +1773,7 @@ static inline void do_generic_file_read(struct file * filp, loff_t *ppos,
actor);
}
#ifdef CONFIG_BLOCK
ssize_t __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
struct block_device *bdev, const struct iovec *iov, loff_t offset,
unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
@ -1793,6 +1811,7 @@ static inline ssize_t blockdev_direct_IO_own_locking(int rw, struct kiocb *iocb,
return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
nr_segs, get_block, end_io, DIO_OWN_LOCKING);
}
#endif
extern const struct file_operations generic_ro_fops;