GFS2: Make writeback more responsive to system conditions

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@redhat.com>

8 files changed, 98 insertions, 90 deletions

diff --git a/fs/gfs2/export.c b/fs/gfs2/export.c
index b5a5e60df0d5..fe9945f2ff72 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 cb8776f0102e..eed4b6855614 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 5067beaffa68..69a63823f7c5 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 9b7b9e40073b..94c3a7db1116 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 842346eae836..8d1344a4e673 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 3ebafa1efad0..03e00417061b 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 0d007f920234..ab0621698b73 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 215c37bfc2a4..58fe3a4ac829 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;