This is a note to let you know that I've just added the patch titled
ext4: allow for the last group to be marked as trimmed
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ext4-allow-for-the-last-group-to-be-marked-as-trimmed.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7c784d624819acbeefb0018bac89e632467cca5a Mon Sep 17 00:00:00 2001
From: Suraj Jitindar Singh <surajjs@xxxxxxxxxx>
Date: Wed, 13 Dec 2023 16:16:35 +1100
Subject: ext4: allow for the last group to be marked as trimmed
From: Suraj Jitindar Singh <surajjs@xxxxxxxxxx>
commit 7c784d624819acbeefb0018bac89e632467cca5a upstream.
The ext4 filesystem tracks the trim status of blocks at the group
level. When an entire group has been trimmed then it is marked as
such and subsequent trim invocations with the same minimum trim size
will not be attempted on that group unless it is marked as able to be
trimmed again such as when a block is freed.
Currently the last group can't be marked as trimmed due to incorrect
logic in ext4_last_grp_cluster(). ext4_last_grp_cluster() is supposed
to return the zero based index of the last cluster in a group. This is
then used by ext4_try_to_trim_range() to determine if the trim
operation spans the entire group and as such if the trim status of the
group should be recorded.
ext4_last_grp_cluster() takes a 0 based group index, thus the valid
values for grp are 0..(ext4_get_groups_count - 1). Any group index
less than (ext4_get_groups_count - 1) is not the last group and must
have EXT4_CLUSTERS_PER_GROUP(sb) clusters. For the last group we need
to calculate the number of clusters based on the number of blocks in
the group. Finally subtract 1 from the number of clusters as zero
based indexing is expected. Rearrange the function slightly to make
it clear what we are calculating and returning.
Reproducer:
// Create file system where the last group has fewer blocks than
// blocks per group
$ mkfs.ext4 -b 4096 -g 8192 /dev/nvme0n1 8191
$ mount /dev/nvme0n1 /mnt
Before Patch:
$ fstrim -v /mnt
/mnt: 25.9 MiB (27156480 bytes) trimmed
// Group not marked as trimmed so second invocation still discards blocks
$ fstrim -v /mnt
/mnt: 25.9 MiB (27156480 bytes) trimmed
After Patch:
fstrim -v /mnt
/mnt: 25.9 MiB (27156480 bytes) trimmed
// Group marked as trimmed so second invocation DOESN'T discard any blocks
fstrim -v /mnt
/mnt: 0 B (0 bytes) trimmed
Fixes: 45e4ab320c9b ("ext4: move setting of trimmed bit into ext4_try_to_trim_range()")
Cc: <stable@xxxxxxxxxxxxxxx> # 4.19+
Signed-off-by: Suraj Jitindar Singh <surajjs@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Link: https://lore.kernel.org/r/20231213051635.37731-1-surajjs@xxxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ext4/mballoc.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -5192,11 +5192,16 @@ __acquires(bitlock)
static ext4_grpblk_t ext4_last_grp_cluster(struct super_block *sb,
ext4_group_t grp)
{
- if (grp < ext4_get_groups_count(sb))
- return EXT4_CLUSTERS_PER_GROUP(sb) - 1;
- return (ext4_blocks_count(EXT4_SB(sb)->s_es) -
- ext4_group_first_block_no(sb, grp) - 1) >>
- EXT4_CLUSTER_BITS(sb);
+ unsigned long nr_clusters_in_group;
+
+ if (grp < (ext4_get_groups_count(sb) - 1))
+ nr_clusters_in_group = EXT4_CLUSTERS_PER_GROUP(sb);
+ else
+ nr_clusters_in_group = (ext4_blocks_count(EXT4_SB(sb)->s_es) -
+ ext4_group_first_block_no(sb, grp))
+ >> EXT4_CLUSTER_BITS(sb);
+
+ return nr_clusters_in_group - 1;
}
static bool ext4_trim_interrupted(void)
Patches currently in stable-queue which might be from surajjs@xxxxxxxxxx are
queue-4.19/ext4-allow-for-the-last-group-to-be-marked-as-trimmed.patch
