From 3c52f7cff01aa766a1d1b2c29abd1175de29edca Mon Sep 17 00:00:00 2001 From: Luca Stefani Date: Tue, 17 Sep 2024 22:33:04 +0200 Subject: [PATCH] btrfs: split remaining space to discard in chunks BugLink: https://bugs.launchpad.net/bugs/2097301 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@vger.kernel.org # 5.15+ Signed-off-by: Luca Stefani Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman Signed-off-by: Manuel Diewald Signed-off-by: Koichiro Den --- fs/btrfs/extent-tree.c | 19 +++++++++++++++---- fs/btrfs/volumes.h | 6 ++++++ 2 files changed, 21 insertions(+), 4 deletions(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 034b75ade35b..d021c6879d7f 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -1330,13 +1330,24 @@ static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len, 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; } diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index 53f87f398da7..25e41ce082f2 100644 --- 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