From d785a06a0b9d0cd86b3cc1bf8e236e62af7b47ed Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 26 Jun 2006 00:27:48 -0700 Subject: [PATCH] md/bitmap: change md/bitmap file handling to use bmap to file blocks If md is asked to store a bitmap in a file, it tries to hold onto the page cache pages for that file, manipulate them directly, and call a cocktail of operations to write the file out. I don't believe this is a supportable approach. This patch changes the approach to use the same approach as swap files. i.e. bmap is used to enumerate all the block address of parts of the file and we write directly to those blocks of the device. swapfile only uses parts of the file that provide a full pages at contiguous addresses. We don't have that luxury so we have to cope with pages that are non-contiguous in storage. To handle this we attach buffers to each page, and store the addresses in those buffers. With this approach the pagecache may contain data which is inconsistent with what is on disk. To alleviate the problems this can cause, md invalidates the pagecache when releasing the file. If the file is to be examined while the array is active (a non-critical but occasionally useful function), O_DIRECT io must be used. And new version of mdadm will have support for this. This approach simplifies a lot of code: - we no longer need to keep a list of pages which we need to wait for, as the b_endio function can keep track of how many outstanding writes there are. This saves a mempool. - -EAGAIN returns from write_page are no longer possible (not sure if they ever were actually). Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/raid/bitmap.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/raid/bitmap.h b/include/linux/raid/bitmap.h index 9c8907ca60a7..63df898fe2e9 100644 --- a/include/linux/raid/bitmap.h +++ b/include/linux/raid/bitmap.h @@ -140,6 +140,7 @@ typedef __u16 bitmap_counter_t; enum bitmap_state { BITMAP_ACTIVE = 0x001, /* the bitmap is in use */ BITMAP_STALE = 0x002, /* the bitmap file is out of date or had -EIO */ + BITMAP_WRITE_ERROR = 0x004, /* A write error has occurred */ BITMAP_HOSTENDIAN = 0x8000, }; @@ -244,9 +245,9 @@ struct bitmap { unsigned long daemon_lastrun; /* jiffies of last run */ unsigned long daemon_sleep; /* how many seconds between updates? */ - spinlock_t write_lock; - struct list_head complete_pages; - mempool_t *write_pool; + atomic_t pending_writes; /* pending writes to the bitmap file */ + wait_queue_head_t write_wait; + }; /* the bitmap API */ -- cgit v1.2.3