From: Luca Stefani <luca.stefani.ge1@xxxxxxxxx> commit a99fcb0158978ed332009449b484e5f3ca2d7df4 upstream. Per Qu Wenruo in case we have a very large disk, e.g. 8TiB device, mostly empty although we will do the split according to our super block locations, the last super block ends at 256G, we can submit a huge discard for the range [256G, 8T), causing a large delay. Split the space left to discard based on BTRFS_MAX_DISCARD_CHUNK_SIZE in preparation of introduction of cancellation points to trim. The value of the chunk size is arbitrary, it can be higher or derived from actual device capabilities but we can't easily read that using bio_discard_limit(). Link: https://bugzilla.kernel.org/show_bug.cgi?id=219180 Link: https://bugzilla.suse.com/show_bug.cgi?id=1229737 CC: stable@xxxxxxxxxxxxxxx # 5.15+ Signed-off-by: Luca Stefani <luca.stefani.ge1@xxxxxxxxx> Reviewed-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: David Sterba <dsterba@xxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/btrfs/extent-tree.c | 19 +++++++++++++++---- fs/btrfs/volumes.h | 6 ++++++ 2 files changed, 21 insertions(+), 4 deletions(-) --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -1303,13 +1303,24 @@ static int btrfs_issue_discard(struct bl bytes_left = end - start; } - if (bytes_left) { + while (bytes_left) { + u64 bytes_to_discard = min(BTRFS_MAX_DISCARD_CHUNK_SIZE, bytes_left); + ret = blkdev_issue_discard(bdev, start >> SECTOR_SHIFT, - bytes_left >> SECTOR_SHIFT, + bytes_to_discard >> SECTOR_SHIFT, GFP_NOFS); - if (!ret) - *discarded_bytes += bytes_left; + + if (ret) { + if (ret != -EOPNOTSUPP) + break; + continue; + } + + start += bytes_to_discard; + bytes_left -= bytes_to_discard; + *discarded_bytes += bytes_to_discard; } + return ret; } --- a/fs/btrfs/volumes.h +++ b/fs/btrfs/volumes.h @@ -15,6 +15,12 @@ #define BTRFS_MAX_DATA_CHUNK_SIZE (10ULL * SZ_1G) +/* + * Arbitratry maximum size of one discard request to limit potentially long time + * spent in blkdev_issue_discard(). + */ +#define BTRFS_MAX_DISCARD_CHUNK_SIZE (SZ_1G) + extern struct mutex uuid_mutex; #define BTRFS_STRIPE_LEN SZ_64K Patches currently in stable-queue which might be from luca.stefani.ge1@xxxxxxxxx are queue-6.6/btrfs-split-remaining-space-to-discard-in-chunks.patch
