ext4: add support for extent pre-caching
Add a new fiemap flag which forces the all of the extents in an inode
to be cached in the extent_status tree. This is critically important
when using AIO to a preallocated file, since if we need to read in
blocks from the extent tree, the io_submit(2) system call becomes
synchronous, and the AIO is no longer "A", which is bad.
In addition, for most files which have an external leaf tree block,
the cost of caching the information in the extent status tree will be
less than caching the entire 4k block in the buffer cache. So it is
generally a win to keep the extent information cached.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 1dc5df0..0e88a36 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -710,11 +710,8 @@
write_lock(&EXT4_I(inode)->i_es_lock);
es = __es_tree_search(&EXT4_I(inode)->i_es_tree.root, lblk);
- if (es && ((es->es_lblk <= lblk) || (es->es_lblk <= end)))
- goto out;
-
- __es_insert_extent(inode, &newes);
-out:
+ if (!es || es->es_lblk > end)
+ __es_insert_extent(inode, &newes);
write_unlock(&EXT4_I(inode)->i_es_lock);
}
@@ -930,6 +927,12 @@
eia = list_entry(a, struct ext4_inode_info, i_es_lru);
eib = list_entry(b, struct ext4_inode_info, i_es_lru);
+ if (ext4_test_inode_state(&eia->vfs_inode, EXT4_STATE_EXT_PRECACHED) &&
+ !ext4_test_inode_state(&eib->vfs_inode, EXT4_STATE_EXT_PRECACHED))
+ return 1;
+ if (!ext4_test_inode_state(&eia->vfs_inode, EXT4_STATE_EXT_PRECACHED) &&
+ ext4_test_inode_state(&eib->vfs_inode, EXT4_STATE_EXT_PRECACHED))
+ return -1;
if (eia->i_touch_when == eib->i_touch_when)
return 0;
if (time_after(eia->i_touch_when, eib->i_touch_when))
@@ -943,21 +946,13 @@
{
struct ext4_inode_info *ei;
struct list_head *cur, *tmp;
- LIST_HEAD(skiped);
+ LIST_HEAD(skipped);
int ret, nr_shrunk = 0;
+ int retried = 0, skip_precached = 1, nr_skipped = 0;
spin_lock(&sbi->s_es_lru_lock);
- /*
- * If the inode that is at the head of LRU list is newer than
- * last_sorted time, that means that we need to sort this list.
- */
- ei = list_first_entry(&sbi->s_es_lru, struct ext4_inode_info, i_es_lru);
- if (sbi->s_es_last_sorted < ei->i_touch_when) {
- list_sort(NULL, &sbi->s_es_lru, ext4_inode_touch_time_cmp);
- sbi->s_es_last_sorted = jiffies;
- }
-
+retry:
list_for_each_safe(cur, tmp, &sbi->s_es_lru) {
/*
* If we have already reclaimed all extents from extent
@@ -968,9 +963,16 @@
ei = list_entry(cur, struct ext4_inode_info, i_es_lru);
- /* Skip the inode that is newer than the last_sorted time */
- if (sbi->s_es_last_sorted < ei->i_touch_when) {
- list_move_tail(cur, &skiped);
+ /*
+ * Skip the inode that is newer than the last_sorted
+ * time. Normally we try hard to avoid shrinking
+ * precached inodes, but we will as a last resort.
+ */
+ if ((sbi->s_es_last_sorted < ei->i_touch_when) ||
+ (skip_precached && ext4_test_inode_state(&ei->vfs_inode,
+ EXT4_STATE_EXT_PRECACHED))) {
+ nr_skipped++;
+ list_move_tail(cur, &skipped);
continue;
}
@@ -990,11 +992,33 @@
}
/* Move the newer inodes into the tail of the LRU list. */
- list_splice_tail(&skiped, &sbi->s_es_lru);
+ list_splice_tail(&skipped, &sbi->s_es_lru);
+ INIT_LIST_HEAD(&skipped);
+
+ /*
+ * If we skipped any inodes, and we weren't able to make any
+ * forward progress, sort the list and try again.
+ */
+ if ((nr_shrunk == 0) && nr_skipped && !retried) {
+ retried++;
+ list_sort(NULL, &sbi->s_es_lru, ext4_inode_touch_time_cmp);
+ sbi->s_es_last_sorted = jiffies;
+ ei = list_first_entry(&sbi->s_es_lru, struct ext4_inode_info,
+ i_es_lru);
+ /*
+ * If there are no non-precached inodes left on the
+ * list, start releasing precached extents.
+ */
+ if (ext4_test_inode_state(&ei->vfs_inode,
+ EXT4_STATE_EXT_PRECACHED))
+ skip_precached = 0;
+ goto retry;
+ }
+
spin_unlock(&sbi->s_es_lru_lock);
if (locked_ei && nr_shrunk == 0)
- nr_shrunk = __es_try_to_reclaim_extents(ei, nr_to_scan);
+ nr_shrunk = __es_try_to_reclaim_extents(locked_ei, nr_to_scan);
return nr_shrunk;
}
@@ -1069,10 +1093,16 @@
struct rb_node *node;
struct extent_status *es;
int nr_shrunk = 0;
+ static DEFINE_RATELIMIT_STATE(_rs, DEFAULT_RATELIMIT_INTERVAL,
+ DEFAULT_RATELIMIT_BURST);
if (ei->i_es_lru_nr == 0)
return 0;
+ if (ext4_test_inode_state(inode, EXT4_STATE_EXT_PRECACHED) &&
+ __ratelimit(&_rs))
+ ext4_warning(inode->i_sb, "forced shrink of precached extents");
+
node = rb_first(&tree->root);
while (node != NULL) {
es = rb_entry(node, struct extent_status, rb_node);