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Subject[PATCH RFC 4/5] ext4: Prepare ext4_mb_discard_preallocations() for handling EXT4_MB_HINT_GOAL_ONLY
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EXT4_MB_HINT_GOAL_ONLY is currently unused. This patch teaches
ext4_mb_discard_preallocations() to discard only that preallocated
range, which contains a specified block, in case of the flag is set.
Otherwise, a preallocated range is not discarded.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
fs/ext4/mballoc.c | 28 +++++++++++++++++++++-------
1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 51a78eb65f3c..b1b3c5526d1a 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3894,8 +3894,8 @@ ext4_mb_release_group_pa(struct ext4_buddy *e4b,
* 1) how many requested
*/
static noinline_for_stack int
-ext4_mb_discard_group_preallocations(struct super_block *sb,
- ext4_group_t group, int needed)
+ext4_mb_discard_group_preallocations(struct super_block *sb, ext4_group_t group,
+ int needed, ext4_fsblk_t goal)
{
struct ext4_group_info *grp = ext4_get_group_info(sb, group);
struct buffer_head *bitmap_bh = NULL;
@@ -3947,6 +3947,12 @@ ext4_mb_discard_group_preallocations(struct super_block *sb,
continue;
}

+ if (goal != (ext4_fsblk_t)-1 &&
+ (goal < pa->pa_pstart || goal >= pa->pa_pstart + pa->pa_len)) {
+ spin_unlock(&pa->pa_lock);
+ continue;
+ }
+
/* seems this one can be freed ... */
pa->pa_deleted = 1;

@@ -4462,15 +4468,23 @@ static int ext4_mb_release_context(struct ext4_allocation_context *ac)
return 0;
}

-static int ext4_mb_discard_preallocations(struct super_block *sb, int needed)
+static int ext4_mb_discard_preallocations(struct super_block *sb,
+ struct ext4_allocation_context *ac)
{
- ext4_group_t i, ngroups = ext4_get_groups_count(sb);
+ ext4_group_t i = 0, ngroups = ext4_get_groups_count(sb);
+ int needed = ac->ac_o_ex.fe_len;
+ ext4_fsblk_t goal = (ext4_fsblk_t)-1;
int ret;
int freed = 0;

+ if (ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY) {
+ i = ac->ac_o_ex.fe_group;
+ ngroups = i + 1;
+ goal = ext4_grp_offs_to_block(ac->ac_sb, &ac->ac_g_ex);
+ }
trace_ext4_mb_discard_preallocations(sb, needed);
- for (i = 0; i < ngroups && needed > 0; i++) {
- ret = ext4_mb_discard_group_preallocations(sb, i, needed);
+ for (; i < ngroups && needed > 0; i++) {
+ ret = ext4_mb_discard_group_preallocations(sb, i, needed, goal);
freed += ret;
needed -= ret;
}
@@ -4585,7 +4599,7 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle,
ar->len = ac->ac_b_ex.fe_len;
}
} else {
- freed = ext4_mb_discard_preallocations(sb, ac->ac_o_ex.fe_len);
+ freed = ext4_mb_discard_preallocations(sb, ac);
if (freed)
goto repeat;
*errp = -ENOSPC;

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