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writeback: split writeback_inodes_wb

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The case where we have a superblock doesn't require a loop here as we scan
over all inodes in writeback_sb_inodes. Split it out into a separate helper
to make the code simpler.  This also allows to get rid of the sb member in
struct writeback_control, which was rather out of place there.

Also update the comments in writeback_sb_inodes that explain the handling
of inodes from wrong superblocks.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Christoph Hellwig 2010-06-10 12:07:54 +02:00 committed by Jens Axboe
parent 9c3a8ee8a1
commit edadfb10ba
2 changed files with 46 additions and 38 deletions
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82
fs/fs-writeback.c
View file

@ -554,29 +554,41 @@ static bool pin_sb_for_writeback(struct super_block *sb)
/*
* Write a portion of b_io inodes which belong to @sb.
* If @wbc->sb != NULL, then find and write all such
*
* If @only_this_sb is true, then find and write all such
* inodes. Otherwise write only ones which go sequentially
* in reverse order.
*
* Return 1, if the caller writeback routine should be
* interrupted. Otherwise return 0.
*/
static int writeback_sb_inodes(struct super_block *sb,
struct bdi_writeback *wb,
struct writeback_control *wbc)
static int writeback_sb_inodes(struct super_block *sb, struct bdi_writeback *wb,
struct writeback_control *wbc, bool only_this_sb)
{
while (!list_empty(&wb->b_io)) {
long pages_skipped;
struct inode *inode = list_entry(wb->b_io.prev,
struct inode, i_list);
if (wbc->sb && sb != inode->i_sb) {
/* super block given and doesn't
match, skip this inode */
redirty_tail(inode);
continue;
}
if (sb != inode->i_sb)
/* finish with this superblock */
if (inode->i_sb != sb) {
if (only_this_sb) {
/*
* We only want to write back data for this
* superblock, move all inodes not belonging
* to it back onto the dirty list.
*/
redirty_tail(inode);
continue;
}
/*
* The inode belongs to a different superblock.
* Bounce back to the caller to unpin this and
* pin the next superblock.
*/
return 0;
}
if (inode->i_state & (I_NEW | I_WILL_FREE)) {
requeue_io(inode);
continue;
@ -629,29 +641,12 @@ void writeback_inodes_wb(struct bdi_writeback *wb,
struct inode, i_list);
struct super_block *sb = inode->i_sb;
if (wbc->sb) {
/*
* We are requested to write out inodes for a specific
* superblock. This means we already have s_umount
* taken by the caller which also waits for us to
* complete the writeout.
*/
if (sb != wbc->sb) {
redirty_tail(inode);
continue;
}
WARN_ON(!rwsem_is_locked(&sb->s_umount));
ret = writeback_sb_inodes(sb, wb, wbc);
} else {
if (!pin_sb_for_writeback(sb)) {
requeue_io(inode);
continue;
}
ret = writeback_sb_inodes(sb, wb, wbc);
drop_super(sb);
if (!pin_sb_for_writeback(sb)) {
requeue_io(inode);
continue;
}
ret = writeback_sb_inodes(sb, wb, wbc, false);
drop_super(sb);
if (ret)
break;
@ -660,6 +655,19 @@ void writeback_inodes_wb(struct bdi_writeback *wb,
/* Leave any unwritten inodes on b_io */
}
static void __writeback_inodes_sb(struct super_block *sb,
struct bdi_writeback *wb, struct writeback_control *wbc)
{
WARN_ON(!rwsem_is_locked(&sb->s_umount));
wbc->wb_start = jiffies; /* livelock avoidance */
spin_lock(&inode_lock);
if (!wbc->for_kupdate || list_empty(&wb->b_io))
queue_io(wb, wbc->older_than_this);
writeback_sb_inodes(sb, wb, wbc, true);
spin_unlock(&inode_lock);
}
/*
* The maximum number of pages to writeout in a single bdi flush/kupdate
* operation. We do this so we don't hold I_SYNC against an inode for
@ -698,7 +706,6 @@ static long wb_writeback(struct bdi_writeback *wb,
struct wb_writeback_args *args)
{
struct writeback_control wbc = {
.sb = args->sb,
.sync_mode = args->sync_mode,
.older_than_this = NULL,
.for_kupdate = args->for_kupdate,
@ -736,7 +743,10 @@ static long wb_writeback(struct bdi_writeback *wb,
wbc.more_io = 0;
wbc.nr_to_write = MAX_WRITEBACK_PAGES;
wbc.pages_skipped = 0;
writeback_inodes_wb(wb, &wbc);
if (args->sb)
__writeback_inodes_sb(args->sb, wb, &wbc);
else
writeback_inodes_wb(wb, &wbc);
args->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write;

2
include/linux/writeback.h
View file

@ -27,8 +27,6 @@ enum writeback_sync_modes {
* in a manner such that unspecified fields are set to zero.
*/
struct writeback_control {
struct super_block *sb; /* if !NULL, only write inodes from
this super_block */
enum writeback_sync_modes sync_mode;
unsigned long *older_than_this; /* If !NULL, only write back inodes
older than this */