bcachefs: BCH_SB_RESERVE_BYTES

Add an option, gc_reserve_bytes, to set the copygc reserve as a size
instead of a percent

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/alloc.c b/fs/bcachefs/alloc.c
index bde22df251349067aa2543a4e014ad2a72cfab4d..e6aeab0b47c7ed7672b1622b075aea9af94deb01 100644 (file)
--- a/fs/bcachefs/alloc.c
+++ b/fs/bcachefs/alloc.c
@@ -1711,7 +1711,7 @@ void bch2_alloc_sectors_done(struct bch_fs *c, struct write_point *wp)
 void bch2_recalc_capacity(struct bch_fs *c)
 {
        struct bch_dev *ca;
-       u64 capacity = 0, reserved_sectors = 0;
+       u64 capacity = 0, reserved_sectors = 0, gc_reserve;
        unsigned long ra_pages = 0;
        unsigned i, j;
 
@@ -1726,7 +1726,7 @@ void bch2_recalc_capacity(struct bch_fs *c)
        bch2_set_ra_pages(c, ra_pages);
 
        for_each_rw_member(ca, c, i) {
-               u64 dev_capacity, dev_reserve = 0;
+               u64 dev_reserve = 0;
 
                /*
                 * We need to reserve buckets (from the number
@@ -1758,25 +1758,21 @@ void bch2_recalc_capacity(struct bch_fs *c)
 
                dev_reserve *= ca->mi.bucket_size;
 
-               dev_reserve *= 2;
+               ca->copygc_threshold = dev_reserve;
 
-               dev_capacity = bucket_to_sector(ca, ca->mi.nbuckets -
-                                               ca->mi.first_bucket);
+               capacity += bucket_to_sector(ca, ca->mi.nbuckets -
+                                            ca->mi.first_bucket);
 
-               ca->copygc_threshold =
-                       max(div64_u64(dev_capacity *
-                                     c->opts.gc_reserve_percent, 100),
-                           dev_reserve) / 2;
-
-               capacity += dev_capacity;
-               reserved_sectors += dev_reserve;
+               reserved_sectors += dev_reserve * 2;
        }
 
-       reserved_sectors = max(div64_u64(capacity *
-                                        c->opts.gc_reserve_percent, 100),
-                              reserved_sectors);
+       gc_reserve = c->opts.gc_reserve_bytes
+               ? c->opts.gc_reserve_bytes >> 9
+               : div64_u64(capacity * c->opts.gc_reserve_percent, 100);
+
+       reserved_sectors = max(gc_reserve, reserved_sectors);
 
-       BUG_ON(reserved_sectors > capacity);
+       reserved_sectors = min(reserved_sectors, capacity);
 
        c->capacity = capacity - reserved_sectors;
 

diff --git a/fs/bcachefs/bcachefs_format.h b/fs/bcachefs/bcachefs_format.h
index eb14dba87402efd6c0c486d2e22c52a7702fbdf5..ac0c7d6a07fbfa09ba273e5b4178449bc01bace5 100644 (file)
--- a/fs/bcachefs/bcachefs_format.h
+++ b/fs/bcachefs/bcachefs_format.h
@@ -1221,6 +1221,7 @@ LE64_BITMASK(BCH_SB_BACKGROUND_TARGET,    struct bch_sb, flags[1], 52, 64);
 
 LE64_BITMASK(BCH_SB_BACKGROUND_COMPRESSION_TYPE,
                                        struct bch_sb, flags[2],  0,  4);
+LE64_BITMASK(BCH_SB_GC_RESERVE_BYTES,  struct bch_sb, flags[2],  4, 64);
 
 /* Features: */
 enum bch_sb_features {

diff --git a/fs/bcachefs/opts.h b/fs/bcachefs/opts.h
index 3b5eddbf56bf543b96f08cccf765124c5a30f74b..01f1cb53eb5f7d9e28cf273f4b4e5ea54cd695d5 100644 (file)
--- a/fs/bcachefs/opts.h
+++ b/fs/bcachefs/opts.h
@@ -114,9 +114,12 @@ enum opt_type {
        BCH_OPT(inodes_32bit,           u8,     OPT_RUNTIME,            \
                OPT_BOOL(),                                             \
                BCH_SB_INODE_32BIT,             false)                  \
-       BCH_OPT(gc_reserve_percent,     u8,     OPT_MOUNT,              \
+       BCH_OPT(gc_reserve_percent,     u8,     OPT_RUNTIME,            \
                OPT_UINT(5, 21),                                        \
                BCH_SB_GC_RESERVE,              8)                      \
+       BCH_OPT(gc_reserve_bytes,       u64,    OPT_RUNTIME,            \
+               OPT_UINT(0, U64_MAX),                                   \
+               BCH_SB_GC_RESERVE_BYTES,        0)                      \
        BCH_OPT(root_reserve_percent,   u8,     OPT_MOUNT,              \
                OPT_UINT(0, 100),                                       \
                BCH_SB_ROOT_RESERVE,            0)                      \