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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

11
fs/proc/proc_misc.c
View file

@ -277,12 +277,15 @@ static int devinfo_show(struct seq_file *f, void *v)
if (i == 0)
seq_printf(f, "Character devices:\n");
chrdev_show(f, i);
} else {
}
#ifdef CONFIG_BLOCK
else {
i -= CHRDEV_MAJOR_HASH_SIZE;
if (i == 0)
seq_printf(f, "\nBlock devices:\n");
blkdev_show(f, i);
}
#endif
return 0;
}
@ -355,6 +358,7 @@ static int stram_read_proc(char *page, char **start, off_t off,
}
#endif
#ifdef CONFIG_BLOCK
extern struct seq_operations partitions_op;
static int partitions_open(struct inode *inode, struct file *file)
{
@ -378,6 +382,7 @@ static struct file_operations proc_diskstats_operations = {
.llseek = seq_lseek,
.release = seq_release,
};
#endif
#ifdef CONFIG_MODULES
extern struct seq_operations modules_op;
@ -695,7 +700,9 @@ void __init proc_misc_init(void)
entry->proc_fops = &proc_kmsg_operations;
create_seq_entry("devices", 0, &proc_devinfo_operations);
create_seq_entry("cpuinfo", 0, &proc_cpuinfo_operations);
#ifdef CONFIG_BLOCK
create_seq_entry("partitions", 0, &proc_partitions_operations);
#endif
create_seq_entry("stat", 0, &proc_stat_operations);
create_seq_entry("interrupts", 0, &proc_interrupts_operations);
#ifdef CONFIG_SLAB
@ -707,7 +714,9 @@ void __init proc_misc_init(void)
create_seq_entry("buddyinfo",S_IRUGO, &fragmentation_file_operations);
create_seq_entry("vmstat",S_IRUGO, &proc_vmstat_file_operations);
create_seq_entry("zoneinfo",S_IRUGO, &proc_zoneinfo_file_operations);
#ifdef CONFIG_BLOCK
create_seq_entry("diskstats", 0, &proc_diskstats_operations);
#endif
#ifdef CONFIG_MODULES
create_seq_entry("modules", 0, &proc_modules_operations);
#endif