From 50a7b899a0d806f961edadfc3357cb6679826795 Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Sun, 4 May 2025 16:31:40 -0400 Subject: [PATCH] bcachefs: Ensure proper write alignment There was a buggy version of bcachefs-tools which picked misaligned bucket sizes when formatting, and we're also about to do dynamic block sizes - which will allow picking logical block size or physical block size of the device per-write, allowing for better compression ratios at the cost of slightly worse write performance (i.e. forcing the device to do RMW or extra buffering). To account for this, tweak bch2_alloc_sectors_start() to properly align open_buckets to the blocksize of the write we're about to do. Signed-off-by: Kent Overstreet --- fs/bcachefs/alloc_foreground.c | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) diff --git a/fs/bcachefs/alloc_foreground.c b/fs/bcachefs/alloc_foreground.c index effafc3e0ced4..7ec022e9361ae 100644 --- a/fs/bcachefs/alloc_foreground.c +++ b/fs/bcachefs/alloc_foreground.c @@ -1422,11 +1422,31 @@ alloc_done: wp->sectors_free = UINT_MAX; - open_bucket_for_each(c, &wp->ptrs, ob, i) + open_bucket_for_each(c, &wp->ptrs, ob, i) { + /* + * Ensure proper write alignment - either due to misaligned + * bucket sizes (from buggy bcachefs-tools), or writes that mix + * logical/physical alignment: + */ + struct bch_dev *ca = ob_dev(c, ob); + u64 offset = bucket_to_sector(ca, ob->bucket) + + ca->mi.bucket_size - + ob->sectors_free; + unsigned align = round_up(offset, block_sectors(c)) - offset; + + ob->sectors_free = max_t(int, 0, ob->sectors_free - align); + wp->sectors_free = min(wp->sectors_free, ob->sectors_free); + } wp->sectors_free = rounddown(wp->sectors_free, block_sectors(c)); + /* Did alignment use up space in an open_bucket? */ + if (unlikely(!wp->sectors_free)) { + bch2_alloc_sectors_done(c, wp); + goto retry; + } + BUG_ON(!wp->sectors_free || wp->sectors_free == UINT_MAX); return 0; -- 2.39.5