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md: make bitmap file support optional

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The support for write intent bitmaps in files on an external files in md
is a hot mess that abuses ->bmap to map file offsets into physical device
objects, and also abuses buffer_heads in a creative way.

Make this code optional so that MD can be built into future kernels
without buffer_head support, and so that we can eventually deprecate it.

Note this does not affect the internal bitmap support, which has none of
the problems.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230615064840.629492-11-hch@lst.de
This commit is contained in:
Christoph Hellwig 2023-06-15 08:48:39 +02:00 committed by Song Liu
parent d7038f9518
commit a34d4ef82c
3 changed files with 32 additions and 0 deletions
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10
drivers/md/Kconfig
View file

@ -50,6 +50,16 @@ config MD_AUTODETECT
If unsure, say Y.
config MD_BITMAP_FILE
bool "MD bitmap file support"
default y
help
If you say Y here, support for write intent bitmaps in files on an
external file system is enabled. This is an alternative to the internal
bitmaps near the MD superblock, and very problematic code that abuses
various kernel APIs and can only work with files on a file system not
actually sitting on the MD device.
config MD_LINEAR
tristate "Linear (append) mode (deprecated)"
depends on BLK_DEV_MD

15
drivers/md/md-bitmap.c
View file

@ -295,6 +295,7 @@ static void write_sb_page(struct bitmap *bitmap, unsigned long pg_index,
static void md_bitmap_file_kick(struct bitmap *bitmap);
#ifdef CONFIG_MD_BITMAP_FILE
static void write_file_page(struct bitmap *bitmap, struct page *page, int wait)
{
struct buffer_head *bh = page_buffers(page);
@ -408,6 +409,20 @@ static int read_file_page(struct file *file, unsigned long index,
ret);
return ret;
}
#else /* CONFIG_MD_BITMAP_FILE */
static void write_file_page(struct bitmap *bitmap, struct page *page, int wait)
{
}
static int read_file_page(struct file *file, unsigned long index,
struct bitmap *bitmap, unsigned long count, struct page *page)
{
return -EIO;
}
static void free_buffers(struct page *page)
{
put_page(page);
}
#endif /* CONFIG_MD_BITMAP_FILE */
/*
* bitmap file superblock operations

7
drivers/md/md.c
View file

@ -7043,6 +7043,13 @@ static int set_bitmap_file(struct mddev *mddev, int fd)
if (mddev->bitmap || mddev->bitmap_info.file)
return -EEXIST; /* cannot add when bitmap is present */
if (!IS_ENABLED(CONFIG_MD_BITMAP_FILE)) {
pr_warn("%s: bitmap files not supported by this kernel\n",
mdname(mddev));
return -EINVAL;
}
f = fget(fd);
if (f == NULL) {