[PATCH 13/32] GFS2: Make writeback more responsive to system conditions

From: Steven Whitehouse
Date: Thu May 19 2011 - 05:14:33 EST

This patch adds writeback_control to writing back the AIL
list. This means that we can then take advantage of the
information we get in ->write_inode() in order to set off
some pre-emptive writeback.

In addition, the AIL code is cleaned up a bit to make it
a bit simpler to understand.

There is still more which can usefully be done in this area,
but this is a good start at least.

Signed-off-by: Steven Whitehouse <swhiteho@xxxxxxxxxx>

diff --git a/fs/gfs2/export.c b/fs/gfs2/export.c
index b5a5e60..fe9945f 100644
--- a/fs/gfs2/export.c
+++ b/fs/gfs2/export.c
@@ -139,7 +139,7 @@ static struct dentry *gfs2_get_dentry(struct super_block *sb,
struct gfs2_sbd *sdp = sb->s_fs_info;
struct inode *inode;

- inode = gfs2_ilookup(sb, inum->no_addr);
+ inode = gfs2_ilookup(sb, inum->no_addr, 0);
if (inode) {
if (GFS2_I(inode)->i_no_formal_ino != inum->no_formal_ino) {
iput(inode);
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index cb8776f..eed4b68 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -649,7 +649,7 @@ static void delete_work_func(struct work_struct *work)
/* Note: Unsafe to dereference ip as we don't hold right refs/locks */

if (ip)
- inode = gfs2_ilookup(sdp->sd_vfs, no_addr);
+ inode = gfs2_ilookup(sdp->sd_vfs, no_addr, 1);
else
inode = gfs2_lookup_by_inum(sdp, no_addr, NULL, GFS2_BLKST_UNLINKED);
if (inode && !IS_ERR(inode)) {
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 5067bea..69a6382 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -20,7 +20,6 @@

#define DIO_WAIT 0x00000010
#define DIO_METADATA 0x00000020
-#define DIO_ALL 0x00000100

struct gfs2_log_operations;
struct gfs2_log_element;
@@ -377,8 +376,6 @@ struct gfs2_ail {
unsigned int ai_first;
struct list_head ai_ail1_list;
struct list_head ai_ail2_list;
-
- u64 ai_sync_gen;
};

struct gfs2_journal_extent {
@@ -657,7 +654,6 @@ struct gfs2_sbd {
spinlock_t sd_ail_lock;
struct list_head sd_ail1_list;
struct list_head sd_ail2_list;
- u64 sd_ail_sync_gen;

/* Replay stuff */

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 9b7b9e4..94c3a7d 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -74,14 +74,14 @@ static int iget_set(struct inode *inode, void *opaque)
return 0;
}

-struct inode *gfs2_ilookup(struct super_block *sb, u64 no_addr)
+struct inode *gfs2_ilookup(struct super_block *sb, u64 no_addr, int non_block)
{
unsigned long hash = (unsigned long)no_addr;
struct gfs2_skip_data data;

data.no_addr = no_addr;
data.skipped = 0;
- data.non_block = 0;
+ data.non_block = non_block;
return ilookup5(sb, hash, iget_test, &data);
}

diff --git a/fs/gfs2/inode.h b/fs/gfs2/inode.h
index 842346e..8d1344a 100644
--- a/fs/gfs2/inode.h
+++ b/fs/gfs2/inode.h
@@ -102,7 +102,7 @@ extern struct inode *gfs2_inode_lookup(struct super_block *sb, unsigned type,
extern struct inode *gfs2_lookup_by_inum(struct gfs2_sbd *sdp, u64 no_addr,
u64 *no_formal_ino,
unsigned int blktype);
-extern struct inode *gfs2_ilookup(struct super_block *sb, u64 no_addr);
+extern struct inode *gfs2_ilookup(struct super_block *sb, u64 no_addr, int nonblock);

extern int gfs2_inode_refresh(struct gfs2_inode *ip);

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 3ebafa1..03e0041 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -18,6 +18,7 @@
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/bio.h>
+#include <linux/writeback.h>

#include "gfs2.h"
#include "incore.h"
@@ -83,50 +84,90 @@ void gfs2_remove_from_ail(struct gfs2_bufdata *bd)
/**
* gfs2_ail1_start_one - Start I/O on a part of the AIL
* @sdp: the filesystem
- * @tr: the part of the AIL
+ * @wbc: The writeback control structure
+ * @ai: The ail structure
*
*/

-static void gfs2_ail1_start_one(struct gfs2_sbd *sdp, struct gfs2_ail *ai)
+static void gfs2_ail1_start_one(struct gfs2_sbd *sdp,
+ struct writeback_control *wbc,
+ struct gfs2_ail *ai)
__releases(&sdp->sd_ail_lock)
__acquires(&sdp->sd_ail_lock)
{
struct gfs2_glock *gl = NULL;
+ struct address_space *mapping;
struct gfs2_bufdata *bd, *s;
struct buffer_head *bh;
- int retry;

- do {
- retry = 0;
+restart:
+ list_for_each_entry_safe_reverse(bd, s, &ai->ai_ail1_list, bd_ail_st_list) {
+ bh = bd->bd_bh;

- list_for_each_entry_safe_reverse(bd, s, &ai->ai_ail1_list,
- bd_ail_st_list) {
- bh = bd->bd_bh;
+ gfs2_assert(sdp, bd->bd_ail == ai);

- gfs2_assert(sdp, bd->bd_ail == ai);
+ if (!buffer_busy(bh)) {
+ if (!buffer_uptodate(bh))
+ gfs2_io_error_bh(sdp, bh);
+ list_move(&bd->bd_ail_st_list, &ai->ai_ail2_list);
+ continue;
+ }
+
+ if (!buffer_dirty(bh))
+ continue;
+ if (gl == bd->bd_gl)
+ continue;
+ gl = bd->bd_gl;
+ list_move(&bd->bd_ail_st_list, &ai->ai_ail1_list);
+ mapping = bh->b_page->mapping;
+ spin_unlock(&sdp->sd_ail_lock);
+ generic_writepages(mapping, wbc);
+ spin_lock(&sdp->sd_ail_lock);
+ if (wbc->nr_to_write <= 0)
+ break;
+ goto restart;
+ }
+}

- if (!buffer_busy(bh)) {
- if (!buffer_uptodate(bh))
- gfs2_io_error_bh(sdp, bh);
- list_move(&bd->bd_ail_st_list, &ai->ai_ail2_list);
- continue;
- }

- if (!buffer_dirty(bh))
- continue;
- if (gl == bd->bd_gl)
- continue;
- gl = bd->bd_gl;
- list_move(&bd->bd_ail_st_list, &ai->ai_ail1_list);
+/**
+ * gfs2_ail1_flush - start writeback of some ail1 entries
+ * @sdp: The super block
+ * @wbc: The writeback control structure
+ *
+ * Writes back some ail1 entries, according to the limits in the
+ * writeback control structure
+ */

- spin_unlock(&sdp->sd_ail_lock);
- filemap_fdatawrite(gfs2_glock2aspace(gl));
- spin_lock(&sdp->sd_ail_lock);
+void gfs2_ail1_flush(struct gfs2_sbd *sdp, struct writeback_control *wbc)
+{
+ struct list_head *head = &sdp->sd_ail1_list;
+ struct gfs2_ail *ai;

- retry = 1;
+ spin_lock(&sdp->sd_ail_lock);
+ list_for_each_entry_reverse(ai, head, ai_list) {
+ if (wbc->nr_to_write <= 0)
break;
- }
- } while (retry);
+ gfs2_ail1_start_one(sdp, wbc, ai); /* This may drop ail lock */
+ }
+ spin_unlock(&sdp->sd_ail_lock);
+}
+
+/**
+ * gfs2_ail1_start - start writeback of all ail1 entries
+ * @sdp: The superblock
+ */
+
+static void gfs2_ail1_start(struct gfs2_sbd *sdp)
+{
+ struct writeback_control wbc = {
+ .sync_mode = WB_SYNC_NONE,
+ .nr_to_write = LONG_MAX,
+ .range_start = 0,
+ .range_end = LLONG_MAX,
+ };
+
+ return gfs2_ail1_flush(sdp, &wbc);
}

/**
@@ -136,7 +177,7 @@ __acquires(&sdp->sd_ail_lock)
*
*/

-static int gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_ail *ai, int flags)
+static void gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_ail *ai)
{
struct gfs2_bufdata *bd, *s;
struct buffer_head *bh;
@@ -144,71 +185,37 @@ static int gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_ail *ai, int fl
list_for_each_entry_safe_reverse(bd, s, &ai->ai_ail1_list,
bd_ail_st_list) {
bh = bd->bd_bh;
-
gfs2_assert(sdp, bd->bd_ail == ai);
-
- if (buffer_busy(bh)) {
- if (flags & DIO_ALL)
- continue;
- else
- break;
- }
-
+ if (buffer_busy(bh))
+ continue;
if (!buffer_uptodate(bh))
gfs2_io_error_bh(sdp, bh);
-
list_move(&bd->bd_ail_st_list, &ai->ai_ail2_list);
}

- return list_empty(&ai->ai_ail1_list);
}

-static void gfs2_ail1_start(struct gfs2_sbd *sdp)
-{
- struct list_head *head;
- u64 sync_gen;
- struct gfs2_ail *ai;
- int done = 0;
-
- spin_lock(&sdp->sd_ail_lock);
- head = &sdp->sd_ail1_list;
- if (list_empty(head)) {
- spin_unlock(&sdp->sd_ail_lock);
- return;
- }
- sync_gen = sdp->sd_ail_sync_gen++;
-
- while(!done) {
- done = 1;
- list_for_each_entry_reverse(ai, head, ai_list) {
- if (ai->ai_sync_gen >= sync_gen)
- continue;
- ai->ai_sync_gen = sync_gen;
- gfs2_ail1_start_one(sdp, ai); /* This may drop ail lock */
- done = 0;
- break;
- }
- }
-
- spin_unlock(&sdp->sd_ail_lock);
-}
+/**
+ * gfs2_ail1_empty - Try to empty the ail1 lists
+ * @sdp: The superblock
+ *
+ * Tries to empty the ail1 lists, starting with the oldest first
+ */

-static int gfs2_ail1_empty(struct gfs2_sbd *sdp, int flags)
+static int gfs2_ail1_empty(struct gfs2_sbd *sdp)
{
struct gfs2_ail *ai, *s;
int ret;

spin_lock(&sdp->sd_ail_lock);
-
list_for_each_entry_safe_reverse(ai, s, &sdp->sd_ail1_list, ai_list) {
- if (gfs2_ail1_empty_one(sdp, ai, flags))
+ gfs2_ail1_empty_one(sdp, ai);
+ if (list_empty(&ai->ai_ail1_list))
list_move(&ai->ai_list, &sdp->sd_ail2_list);
- else if (!(flags & DIO_ALL))
+ else
break;
}
-
ret = list_empty(&sdp->sd_ail1_list);
-
spin_unlock(&sdp->sd_ail_lock);

return ret;
@@ -569,7 +576,7 @@ static void log_write_header(struct gfs2_sbd *sdp, u32 flags, int pull)
set_buffer_uptodate(bh);
clear_buffer_dirty(bh);

- gfs2_ail1_empty(sdp, 0);
+ gfs2_ail1_empty(sdp);
tail = current_tail(sdp);

lh = (struct gfs2_log_header *)bh->b_data;
@@ -864,7 +871,7 @@ void gfs2_meta_syncfs(struct gfs2_sbd *sdp)
gfs2_log_flush(sdp, NULL);
for (;;) {
gfs2_ail1_start(sdp);
- if (gfs2_ail1_empty(sdp, DIO_ALL))
+ if (gfs2_ail1_empty(sdp))
break;
msleep(10);
}
@@ -900,17 +907,15 @@ int gfs2_logd(void *data)

preflush = atomic_read(&sdp->sd_log_pinned);
if (gfs2_jrnl_flush_reqd(sdp) || t == 0) {
- gfs2_ail1_empty(sdp, DIO_ALL);
+ gfs2_ail1_empty(sdp);
gfs2_log_flush(sdp, NULL);
- gfs2_ail1_empty(sdp, DIO_ALL);
}

if (gfs2_ail_flush_reqd(sdp)) {
gfs2_ail1_start(sdp);
io_schedule();
- gfs2_ail1_empty(sdp, 0);
+ gfs2_ail1_empty(sdp);
gfs2_log_flush(sdp, NULL);
- gfs2_ail1_empty(sdp, DIO_ALL);
}

wake_up(&sdp->sd_log_waitq);
diff --git a/fs/gfs2/log.h b/fs/gfs2/log.h
index 0d007f9..ab06216 100644
--- a/fs/gfs2/log.h
+++ b/fs/gfs2/log.h
@@ -12,6 +12,7 @@

#include <linux/list.h>
#include <linux/spinlock.h>
+#include <linux/writeback.h>
#include "incore.h"

/**
@@ -59,6 +60,7 @@ extern struct buffer_head *gfs2_log_fake_buf(struct gfs2_sbd *sdp,
extern void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl);
extern void gfs2_log_commit(struct gfs2_sbd *sdp, struct gfs2_trans *trans);
extern void gfs2_remove_from_ail(struct gfs2_bufdata *bd);
+extern void gfs2_ail1_flush(struct gfs2_sbd *sdp, struct writeback_control *wbc);

extern void gfs2_log_shutdown(struct gfs2_sbd *sdp);
extern void gfs2_meta_syncfs(struct gfs2_sbd *sdp);
diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index 215c37b..58fe3a4 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -23,6 +23,7 @@
#include <linux/time.h>
#include <linux/wait.h>
#include <linux/writeback.h>
+#include <linux/backing-dev.h>

#include "gfs2.h"
#include "incore.h"
@@ -714,6 +715,7 @@ static int gfs2_write_inode(struct inode *inode, struct writeback_control *wbc)
struct gfs2_inode *ip = GFS2_I(inode);
struct gfs2_sbd *sdp = GFS2_SB(inode);
struct address_space *metamapping = gfs2_glock2aspace(ip->i_gl);
+ struct backing_dev_info *bdi = metamapping->backing_dev_info;
struct gfs2_holder gh;
struct buffer_head *bh;
struct timespec atime;
@@ -747,6 +749,8 @@ do_flush:
if (wbc->sync_mode == WB_SYNC_ALL)
gfs2_log_flush(GFS2_SB(inode), ip->i_gl);
filemap_fdatawrite(metamapping);
+ if (bdi->dirty_exceeded)
+ gfs2_ail1_flush(sdp, wbc);
if (!ret && (wbc->sync_mode == WB_SYNC_ALL))
ret = filemap_fdatawait(metamapping);
if (ret)
@@ -1366,7 +1370,8 @@ static int gfs2_dinode_dealloc(struct gfs2_inode *ip)
if (error)
goto out_rindex_relse;

- error = gfs2_trans_begin(sdp, RES_RG_BIT + RES_STATFS + RES_QUOTA, 1);
+ error = gfs2_trans_begin(sdp, RES_RG_BIT + RES_STATFS + RES_QUOTA,
+ sdp->sd_jdesc->jd_blocks);
if (error)
goto out_rg_gunlock;

--
1.7.4

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