Currently ext4_mb_load_buddy is called for every group, irrespective
of whether the group info is already in memory, while reading
/proc/fs/ext4/<partition>/mb_groups proc file. For the purpose of
mb_groups proc file, it is unnecessary to load the file group info
from disk if it was loaded in past. These calls to ext4_mb_load_buddy
make reading the mb_groups proc file expensive.
Also, the locks around ext4_get_group_info are not required.
This patch modifies the code to call ext4_mb_load_buddy only if the
group info had never been loaded into memory in past. It also removes
the mb group locking around ext4_get_group_info call.
Signed-off-by: Aditya Kali <adityakali@xxxxxxxxxx>
---
fs/ext4/mballoc.c | 23 +++++++++++++++--------
1 files changed, 15 insertions(+), 8 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 851f49b..5738082 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2171,8 +2171,9 @@ static int ext4_mb_seq_groups_show(struct
seq_file *seq, void *v)
struct super_block *sb = seq->private;
ext4_group_t group = (ext4_group_t) ((unsigned long) v);
int i;
- int err;
+ int err, buddy_loaded = 0;
struct ext4_buddy e4b;
+ struct ext4_group_info *grinfo;
struct sg {
struct ext4_group_info info;
ext4_grpblk_t counters[16];
@@ -2189,15 +2190,21 @@ static int ext4_mb_seq_groups_show(struct
seq_file *seq, void *v)
i = (sb->s_blocksize_bits + 2) * sizeof(sg.info.bb_counters[0]) +
sizeof(struct ext4_group_info);
- err = ext4_mb_load_buddy(sb, group, &e4b);
- if (err) {
- seq_printf(seq, "#%-5u: I/O error\n", group);
- return 0;
+ grinfo = ext4_get_group_info(sb, group);
+ /* Load the group info in memory only if not already loaded. */
+ if (unlikely(EXT4_MB_GRP_NEED_INIT(grinfo))) {
+ err = ext4_mb_load_buddy(sb, group, &e4b);
+ if (err) {
+ seq_printf(seq, "#%-5u: I/O error\n", group);
+ return 0;
+ }
+ buddy_loaded = 1;
}
- ext4_lock_group(sb, group);
+
memcpy(&sg, ext4_get_group_info(sb, group), i);
- ext4_unlock_group(sb, group);
- ext4_mb_unload_buddy(&e4b);
+
+ if (buddy_loaded)
+ ext4_mb_unload_buddy(&e4b);
seq_printf(seq, "#%-5u: %-5u %-5u %-5u [", group, sg.info.bb_free,
sg.info.bb_fragments, sg.info.bb_first_free);
--
1.7.3.1
--
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