diff options
| -rw-r--r-- | fs/ext4/mballoc.c | 56 |
1 files changed, 51 insertions, 5 deletions
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index b75408d72773..754ff9f65199 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -351,6 +351,35 @@ static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap, ext4_group_t group); static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac); +/* + * The algorithm using this percpu seq counter goes below: + * 1. We sample the percpu discard_pa_seq counter before trying for block + * allocation in ext4_mb_new_blocks(). + * 2. We increment this percpu discard_pa_seq counter when we either allocate + * or free these blocks i.e. while marking those blocks as used/free in + * mb_mark_used()/mb_free_blocks(). + * 3. We also increment this percpu seq counter when we successfully identify + * that the bb_prealloc_list is not empty and hence proceed for discarding + * of those PAs inside ext4_mb_discard_group_preallocations(). + * + * Now to make sure that the regular fast path of block allocation is not + * affected, as a small optimization we only sample the percpu seq counter + * on that cpu. Only when the block allocation fails and when freed blocks + * found were 0, that is when we sample percpu seq counter for all cpus using + * below function ext4_get_discard_pa_seq_sum(). This happens after making + * sure that all the PAs on grp->bb_prealloc_list got freed or if it's empty. + */ +static DEFINE_PER_CPU(u64, discard_pa_seq); +static inline u64 ext4_get_discard_pa_seq_sum(void) +{ + int __cpu; + u64 __seq = 0; + + for_each_possible_cpu(__cpu) + __seq += per_cpu(discard_pa_seq, __cpu); + return __seq; +} + static inline void *mb_correct_addr_and_bit(int *bit, void *addr) { #if BITS_PER_LONG == 64 @@ -1462,6 +1491,7 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b, mb_check_buddy(e4b); mb_free_blocks_double(inode, e4b, first, count); + this_cpu_inc(discard_pa_seq); e4b->bd_info->bb_free += count; if (first < e4b->bd_info->bb_first_free) e4b->bd_info->bb_first_free = first; @@ -1603,6 +1633,7 @@ static int mb_mark_used(struct ext4_buddy *e4b, struct ext4_free_extent *ex) mb_check_buddy(e4b); mb_mark_used_double(e4b, start, len); + this_cpu_inc(discard_pa_seq); e4b->bd_info->bb_free -= len; if (e4b->bd_info->bb_first_free == start) e4b->bd_info->bb_first_free += len; @@ -3962,6 +3993,7 @@ ext4_mb_discard_group_preallocations(struct super_block *sb, INIT_LIST_HEAD(&list); repeat: ext4_lock_group(sb, group); + this_cpu_inc(discard_pa_seq); list_for_each_entry_safe(pa, tmp, &grp->bb_prealloc_list, pa_group_list) { spin_lock(&pa->pa_lock); @@ -4544,14 +4576,26 @@ static int ext4_mb_discard_preallocations(struct super_block *sb, int needed) } static bool ext4_mb_discard_preallocations_should_retry(struct super_block *sb, - struct ext4_allocation_context *ac) + struct ext4_allocation_context *ac, u64 *seq) { int freed; + u64 seq_retry = 0; + bool ret = false; freed = ext4_mb_discard_preallocations(sb, ac->ac_o_ex.fe_len); - if (freed) - return true; - return false; + if (freed) { + ret = true; + goto out_dbg; + } + seq_retry = ext4_get_discard_pa_seq_sum(); + if (seq_retry != *seq) { + *seq = seq_retry; + ret = true; + } + +out_dbg: + mb_debug(sb, "freed %d, retry ? %s\n", freed, ret ? "yes" : "no"); + return ret; } /* @@ -4568,6 +4612,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle, ext4_fsblk_t block = 0; unsigned int inquota = 0; unsigned int reserv_clstrs = 0; + u64 seq; might_sleep(); sb = ar->inode->i_sb; @@ -4630,6 +4675,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle, } ac->ac_op = EXT4_MB_HISTORY_PREALLOC; + seq = *this_cpu_ptr(&discard_pa_seq); if (!ext4_mb_use_preallocated(ac)) { ac->ac_op = EXT4_MB_HISTORY_ALLOC; ext4_mb_normalize_request(ac, ar); @@ -4666,7 +4712,7 @@ repeat: ar->len = ac->ac_b_ex.fe_len; } } else { - if (ext4_mb_discard_preallocations_should_retry(sb, ac)) + if (ext4_mb_discard_preallocations_should_retry(sb, ac, &seq)) goto repeat; /* * If block allocation fails then the pa allocated above |