ext4: Avoid group preallocation for closed files

[mirror_ubuntu-bionic-kernel.git] / fs / ext4 / ext4.h

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 70aa951ecb3c4b01329cfb3f40f664371428f4ea..2e9a2036c11401c1f1586abaf49668100dcab7f9 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -952,6 +952,7 @@ struct ext4_sb_info {
        atomic_t s_mb_lost_chunks;
        atomic_t s_mb_preallocated;
        atomic_t s_mb_discarded;
+       atomic_t s_lock_busy;
 
        /* locality groups */
        struct ext4_locality_group *s_locality_groups;
@@ -1593,15 +1594,42 @@ struct ext4_group_info {
 #define EXT4_MB_GRP_NEED_INIT(grp)     \
        (test_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &((grp)->bb_state)))
 
+#define EXT4_MAX_CONTENTION            8
+#define EXT4_CONTENTION_THRESHOLD      2
+
 static inline spinlock_t *ext4_group_lock_ptr(struct super_block *sb,
                                              ext4_group_t group)
 {
        return bgl_lock_ptr(EXT4_SB(sb)->s_blockgroup_lock, group);
 }
 
+/*
+ * Returns true if the filesystem is busy enough that attempts to
+ * access the block group locks has run into contention.
+ */
+static inline int ext4_fs_is_busy(struct ext4_sb_info *sbi)
+{
+       return (atomic_read(&sbi->s_lock_busy) > EXT4_CONTENTION_THRESHOLD);
+}
+
 static inline void ext4_lock_group(struct super_block *sb, ext4_group_t group)
 {
-       spin_lock(ext4_group_lock_ptr(sb, group));
+       spinlock_t *lock = ext4_group_lock_ptr(sb, group);
+       if (spin_trylock(lock))
+               /*
+                * We're able to grab the lock right away, so drop the
+                * lock contention counter.
+                */
+               atomic_add_unless(&EXT4_SB(sb)->s_lock_busy, -1, 0);
+       else {
+               /*
+                * The lock is busy, so bump the contention counter,
+                * and then wait on the spin lock.
+                */
+               atomic_add_unless(&EXT4_SB(sb)->s_lock_busy, 1,
+                                 EXT4_MAX_CONTENTION);
+               spin_lock(lock);
+       }
 }
 
 static inline void ext4_unlock_group(struct super_block *sb,