From 4b6d287f627b5fb6a49f78f9e81649ff98c62bb7 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Fri, 9 Sep 2005 16:23:47 -0700 Subject: [PATCH] md: add write-behind support for md/raid1 If a device is flagged 'WriteMostly' and the array has a bitmap, and the bitmap superblock indicates that write_behind is allowed, then write_behind is enabled for WriteMostly devices. Write requests will be acknowledges as complete to the caller (via b_end_io) when all non-WriteMostly devices have completed the write, but will not be cleared from the bitmap until all devices complete. This requires memory allocation to make a local copy of the data being written. If there is insufficient memory, then we fall-back on normal write semantics. Signed-Off-By: Paul Clements Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/md/bitmap.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-) (limited to 'drivers/md/bitmap.c') diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c index 2925219f0881..2c84de2b4ad5 100644 --- a/drivers/md/bitmap.c +++ b/drivers/md/bitmap.c @@ -437,6 +437,7 @@ void bitmap_print_sb(struct bitmap *bitmap) printk(KERN_DEBUG " daemon sleep: %ds\n", le32_to_cpu(sb->daemon_sleep)); printk(KERN_DEBUG " sync size: %llu KB\n", (unsigned long long)le64_to_cpu(sb->sync_size)/2); + printk(KERN_DEBUG "max write behind: %d\n", le32_to_cpu(sb->write_behind)); kunmap(bitmap->sb_page); } @@ -445,7 +446,7 @@ static int bitmap_read_sb(struct bitmap *bitmap) { char *reason = NULL; bitmap_super_t *sb; - unsigned long chunksize, daemon_sleep; + unsigned long chunksize, daemon_sleep, write_behind; unsigned long bytes_read; unsigned long long events; int err = -EINVAL; @@ -474,6 +475,7 @@ static int bitmap_read_sb(struct bitmap *bitmap) chunksize = le32_to_cpu(sb->chunksize); daemon_sleep = le32_to_cpu(sb->daemon_sleep); + write_behind = le32_to_cpu(sb->write_behind); /* verify that the bitmap-specific fields are valid */ if (sb->magic != cpu_to_le32(BITMAP_MAGIC)) @@ -485,7 +487,9 @@ static int bitmap_read_sb(struct bitmap *bitmap) else if ((1 << ffz(~chunksize)) != chunksize) reason = "bitmap chunksize not a power of 2"; else if (daemon_sleep < 1 || daemon_sleep > 15) - reason = "daemon sleep period out of range"; + reason = "daemon sleep period out of range (1-15s)"; + else if (write_behind > COUNTER_MAX) + reason = "write-behind limit out of range (0 - 16383)"; if (reason) { printk(KERN_INFO "%s: invalid bitmap file superblock: %s\n", bmname(bitmap), reason); @@ -518,6 +522,7 @@ success: /* assign fields using values from superblock */ bitmap->chunksize = chunksize; bitmap->daemon_sleep = daemon_sleep; + bitmap->max_write_behind = write_behind; bitmap->flags |= sb->state; bitmap->events_cleared = le64_to_cpu(sb->events_cleared); if (sb->state & BITMAP_STALE) @@ -1282,9 +1287,16 @@ static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap, } } -int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors) +int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors, int behind) { if (!bitmap) return 0; + + if (behind) { + atomic_inc(&bitmap->behind_writes); + PRINTK(KERN_DEBUG "inc write-behind count %d/%d\n", + atomic_read(&bitmap->behind_writes), bitmap->max_write_behind); + } + while (sectors) { int blocks; bitmap_counter_t *bmc; @@ -1319,9 +1331,15 @@ int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sect } void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors, - int success) + int success, int behind) { if (!bitmap) return; + if (behind) { + atomic_dec(&bitmap->behind_writes); + PRINTK(KERN_DEBUG "dec write-behind count %d/%d\n", + atomic_read(&bitmap->behind_writes), bitmap->max_write_behind); + } + while (sectors) { int blocks; unsigned long flags; -- cgit v1.2.3