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[PATCH] md: add write-behind support for md/raid1

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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 <paul.clements@steeleye.com>
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
NeilBrown
2005-09-09 16:23:47 -07:00
committed by Linus Torvalds
parent 8ddf9efe67
commit 4b6d287f62
5 changed files with 165 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files
drivers/md/bitmap.c
+22 -4
View File
@@ -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;