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Subject[PATCH v4 02/12] ext4: add a new helper to check if es must be kept
Date
In the extent status tree, we have extents which we can just drop without
issues and extents we must not drop - this depends on the extent's status
- currently ext4_es_is_delayed() extents must stay, others may be dropped.

A helper function is added to help determine if the current extent can
be dropped, although only ext4_es_is_delayed() extents cannot be dropped
currently.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
---
fs/ext4/extents_status.c | 34 +++++++++++++++++++++-------------
1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 7bc221038c6c..573723b23d19 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -448,6 +448,19 @@ static void ext4_es_list_del(struct inode *inode)
spin_unlock(&sbi->s_es_lock);
}

+/*
+ * Returns true if we cannot fail to allocate memory for this extent_status
+ * entry and cannot reclaim it until its status changes.
+ */
+static inline bool ext4_es_must_keep(struct extent_status *es)
+{
+ /* fiemap, bigalloc, and seek_data/hole need to use it. */
+ if (ext4_es_is_delayed(es))
+ return true;
+
+ return false;
+}
+
static struct extent_status *
ext4_es_alloc_extent(struct inode *inode, ext4_lblk_t lblk, ext4_lblk_t len,
ext4_fsblk_t pblk)
@@ -460,10 +473,8 @@ ext4_es_alloc_extent(struct inode *inode, ext4_lblk_t lblk, ext4_lblk_t len,
es->es_len = len;
es->es_pblk = pblk;

- /*
- * We don't count delayed extent because we never try to reclaim them
- */
- if (!ext4_es_is_delayed(es)) {
+ /* We never try to reclaim a must kept extent, so we don't count it. */
+ if (!ext4_es_must_keep(es)) {
if (!EXT4_I(inode)->i_es_shk_nr++)
ext4_es_list_add(inode);
percpu_counter_inc(&EXT4_SB(inode->i_sb)->
@@ -481,8 +492,8 @@ static void ext4_es_free_extent(struct inode *inode, struct extent_status *es)
EXT4_I(inode)->i_es_all_nr--;
percpu_counter_dec(&EXT4_SB(inode->i_sb)->s_es_stats.es_stats_all_cnt);

- /* Decrease the shrink counter when this es is not delayed */
- if (!ext4_es_is_delayed(es)) {
+ /* Decrease the shrink counter when we can reclaim the extent. */
+ if (!ext4_es_must_keep(es)) {
BUG_ON(EXT4_I(inode)->i_es_shk_nr == 0);
if (!--EXT4_I(inode)->i_es_shk_nr)
ext4_es_list_del(inode);
@@ -853,7 +864,7 @@ int ext4_es_insert_extent(struct inode *inode, ext4_lblk_t lblk,
if (err == -ENOMEM && __es_shrink(EXT4_SB(inode->i_sb),
128, EXT4_I(inode)))
goto retry;
- if (err == -ENOMEM && !ext4_es_is_delayed(&newes))
+ if (err == -ENOMEM && !ext4_es_must_keep(&newes))
err = 0;

if (sbi->s_cluster_ratio > 1 && test_opt(inode->i_sb, DELALLOC) &&
@@ -1706,11 +1717,8 @@ static int es_do_reclaim_extents(struct ext4_inode_info *ei, ext4_lblk_t end,

(*nr_to_scan)--;
node = rb_next(&es->rb_node);
- /*
- * We can't reclaim delayed extent from status tree because
- * fiemap, bigallic, and seek_data/hole need to use it.
- */
- if (ext4_es_is_delayed(es))
+
+ if (ext4_es_must_keep(es))
goto next;
if (ext4_es_is_referenced(es)) {
ext4_es_clear_referenced(es);
@@ -1774,7 +1782,7 @@ void ext4_clear_inode_es(struct inode *inode)
while (node) {
es = rb_entry(node, struct extent_status, rb_node);
node = rb_next(node);
- if (!ext4_es_is_delayed(es)) {
+ if (!ext4_es_must_keep(es)) {
rb_erase(&es->rb_node, &tree->root);
ext4_es_free_extent(inode, es);
}
--
2.31.1
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