ext4: Add mount option to set kjournald's I/O priority

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Jens Axboe <jens.axboe@oracle.com>

4 files changed, 36 insertions, 5 deletions

diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 9ec29d86ff8b..8938949b201e 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -308,6 +308,13 @@ min_batch_time=usec	This parameter sets the commit time (as
                         multi-threaded, synchronous workloads on very
                         fast disks, at the cost of increasing latency.
 
+journal_ioprio=prio     The I/O priority (from 0 to 7, where 0 is the
+                        highest priorty) which should be used for I/O
+                        operations submitted by kjournald2 during a
+                        commit operation.  This defaults to 3, which is
+                        a slightly higher priority than the default I/O
+                        priority.
+
 Data Mode
 =========
 There are 3 different data modes:
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 8036392b2121..8ff8709828fd 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1013,7 +1013,7 @@ enum {
         Opt_ignore, Opt_barrier, Opt_err, Opt_resize, Opt_usrquota,
         Opt_grpquota, Opt_extents, Opt_noextents, Opt_i_version,
         Opt_stripe, Opt_delalloc, Opt_nodelalloc,
-        Opt_inode_readahead_blks
+        Opt_inode_readahead_blks, Opt_journal_ioprio
 };
 
 static const match_table_t tokens = {
@@ -1074,6 +1074,7 @@ static const match_table_t tokens = {
         {Opt_delalloc, "delalloc"},
         {Opt_nodelalloc, "nodelalloc"},
         {Opt_inode_readahead_blks, "inode_readahead_blks=%u"},
+        {Opt_journal_ioprio, "journal_ioprio=%u"},
         {Opt_err, NULL},
 };
 
@@ -1098,8 +1099,11 @@ static ext4_fsblk_t get_sb_block(void **data)
         return sb_block;
 }
 
+#define DEFAULT_JOURNAL_IOPRIO (IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, 3))
+
 static int parse_options(char *options, struct super_block *sb,
                          unsigned long *journal_devnum,
+                         unsigned int *journal_ioprio,
                          ext4_fsblk_t *n_blocks_count, int is_remount)
 {
         struct ext4_sb_info *sbi = EXT4_SB(sb);
@@ -1492,6 +1496,14 @@ set_qf_format:
                                 return 0;
                         sbi->s_inode_readahead_blks = option;
                         break;
+                case Opt_journal_ioprio:
+                        if (match_int(&args[0], &option))
+                                return 0;
+                        if (option < 0 || option > 7)
+                                break;
+                        *journal_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE,
+                                                            option);
+                        break;
                 default:
                         printk(KERN_ERR
                                "EXT4-fs: Unrecognized mount option \"%s\" "
@@ -2035,6 +2047,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
         int features;
         __u64 blocks_count;
         int err;
+        unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
 
         sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
         if (!sbi)
@@ -2141,7 +2154,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
         set_opt(sbi->s_mount_opt, DELALLOC);
 
 
-        if (!parse_options((char *) data, sb, &journal_devnum, NULL, 0))
+        if (!parse_options((char *) data, sb, &journal_devnum,
+                           &journal_ioprio, NULL, 0))
                 goto failed_mount;
 
         sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
@@ -2506,6 +2520,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
         default:
                 break;
         }
+        set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);
 
 no_journal:
 
@@ -3127,6 +3142,7 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
         unsigned long old_sb_flags;
         struct ext4_mount_options old_opts;
         ext4_group_t g;
+        unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
         int err;
 #ifdef CONFIG_QUOTA
         int i;
@@ -3145,11 +3161,14 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
         for (i = 0; i < MAXQUOTAS; i++)
                 old_opts.s_qf_names[i] = sbi->s_qf_names[i];
 #endif
+        if (sbi->s_journal && sbi->s_journal->j_task->io_context)
+                journal_ioprio = sbi->s_journal->j_task->io_context->ioprio;
 
         /*
          * Allow the "check" option to be passed as a remount option.
          */
-        if (!parse_options(data, sb, NULL, &n_blocks_count, 1)) {
+        if (!parse_options(data, sb, NULL, &journal_ioprio,
+                           &n_blocks_count, 1)) {
                 err = -EINVAL;
                 goto restore_opts;
         }
@@ -3162,8 +3181,10 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
 
         es = sbi->s_es;
 
-        if (sbi->s_journal)
+        if (sbi->s_journal) {
                 ext4_init_journal_params(sb, sbi->s_journal);
+                set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);
+        }
 
         if ((*flags & MS_RDONLY) != (sb->s_flags & MS_RDONLY) ||
                 n_blocks_count > ext4_blocks_count(es)) {
diff --git a/fs/ioprio.c b/fs/ioprio.c
index 3569e0ad86a2..1a39ac370942 100644
--- a/fs/ioprio.c
+++ b/fs/ioprio.c
@@ -27,7 +27,7 @@
 #include <linux/security.h>
 #include <linux/pid_namespace.h>
 
-static int set_task_ioprio(struct task_struct *task, int ioprio)
+int set_task_ioprio(struct task_struct *task, int ioprio)
 {
         int err;
         struct io_context *ioc;
@@ -70,6 +70,7 @@ static int set_task_ioprio(struct task_struct *task, int ioprio)
         task_unlock(task);
         return err;
 }
+EXPORT_SYMBOL_GPL(set_task_ioprio);
 
 asmlinkage long sys_ioprio_set(int which, int who, int ioprio)
 {
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index f98a656b17e5..76dad4808847 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -86,4 +86,6 @@ static inline int task_nice_ioclass(struct task_struct *task)
  */
 extern int ioprio_best(unsigned short aprio, unsigned short bprio);
 
+extern int set_task_ioprio(struct task_struct *task, int ioprio);
+
 #endif