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author | Josef Bacik <josef@redhat.com> | 2011-01-25 16:30:38 -0500 |
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committer | Josef Bacik <josef@redhat.com> | 2011-03-17 14:21:18 -0400 |
commit | 57a45ced94fe48a701361d64230fc16eefa189dd (patch) | |
tree | 8f0cfe52ba0b3fb8a6ed3cc5d3e7449369b0b9a5 /fs/btrfs/extent-tree.c | |
parent | 4a64001f0047956e283f7ada9843dfc3f3b5d8c8 (diff) | |
download | kernel_samsung_espresso10-57a45ced94fe48a701361d64230fc16eefa189dd.zip kernel_samsung_espresso10-57a45ced94fe48a701361d64230fc16eefa189dd.tar.gz kernel_samsung_espresso10-57a45ced94fe48a701361d64230fc16eefa189dd.tar.bz2 |
Btrfs: change reserved_extents to an atomic_t
We track delayed allocation per inodes via 2 counters, one is
outstanding_extents and reserved_extents. Outstanding_extents is already an
atomic_t, but reserved_extents is not and is protected by a spinlock. So
convert this to an atomic_t and instead of using a spinlock, use atomic_cmpxchg
when releasing delalloc bytes. This makes our inode 72 bytes smaller, and
reduces locking overhead (albiet it was minimal to begin with). Thanks,
Signed-off-by: Josef Bacik <josef@redhat.com>
Diffstat (limited to 'fs/btrfs/extent-tree.c')
-rw-r--r-- | fs/btrfs/extent-tree.c | 42 |
1 files changed, 26 insertions, 16 deletions
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 7b3089b..27376c9 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -3996,6 +3996,7 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes) struct btrfs_block_rsv *block_rsv = &root->fs_info->delalloc_block_rsv; u64 to_reserve; int nr_extents; + int reserved_extents; int ret; if (btrfs_transaction_in_commit(root->fs_info)) @@ -4003,25 +4004,24 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes) num_bytes = ALIGN(num_bytes, root->sectorsize); - spin_lock(&BTRFS_I(inode)->accounting_lock); nr_extents = atomic_read(&BTRFS_I(inode)->outstanding_extents) + 1; - if (nr_extents > BTRFS_I(inode)->reserved_extents) { - nr_extents -= BTRFS_I(inode)->reserved_extents; + reserved_extents = atomic_read(&BTRFS_I(inode)->reserved_extents); + + if (nr_extents > reserved_extents) { + nr_extents -= reserved_extents; to_reserve = calc_trans_metadata_size(root, nr_extents); } else { nr_extents = 0; to_reserve = 0; } - spin_unlock(&BTRFS_I(inode)->accounting_lock); + to_reserve += calc_csum_metadata_size(inode, num_bytes); ret = reserve_metadata_bytes(NULL, root, block_rsv, to_reserve, 1); if (ret) return ret; - spin_lock(&BTRFS_I(inode)->accounting_lock); - BTRFS_I(inode)->reserved_extents += nr_extents; + atomic_add(nr_extents, &BTRFS_I(inode)->reserved_extents); atomic_inc(&BTRFS_I(inode)->outstanding_extents); - spin_unlock(&BTRFS_I(inode)->accounting_lock); block_rsv_add_bytes(block_rsv, to_reserve, 1); @@ -4036,20 +4036,30 @@ void btrfs_delalloc_release_metadata(struct inode *inode, u64 num_bytes) struct btrfs_root *root = BTRFS_I(inode)->root; u64 to_free; int nr_extents; + int reserved_extents; num_bytes = ALIGN(num_bytes, root->sectorsize); atomic_dec(&BTRFS_I(inode)->outstanding_extents); WARN_ON(atomic_read(&BTRFS_I(inode)->outstanding_extents) < 0); - spin_lock(&BTRFS_I(inode)->accounting_lock); - nr_extents = atomic_read(&BTRFS_I(inode)->outstanding_extents); - if (nr_extents < BTRFS_I(inode)->reserved_extents) { - nr_extents = BTRFS_I(inode)->reserved_extents - nr_extents; - BTRFS_I(inode)->reserved_extents -= nr_extents; - } else { - nr_extents = 0; - } - spin_unlock(&BTRFS_I(inode)->accounting_lock); + reserved_extents = atomic_read(&BTRFS_I(inode)->reserved_extents); + do { + int old, new; + + nr_extents = atomic_read(&BTRFS_I(inode)->outstanding_extents); + if (nr_extents >= reserved_extents) { + nr_extents = 0; + break; + } + old = reserved_extents; + nr_extents = reserved_extents - nr_extents; + new = reserved_extents - nr_extents; + old = atomic_cmpxchg(&BTRFS_I(inode)->reserved_extents, + reserved_extents, new); + if (likely(old == reserved_extents)) + break; + reserved_extents = old; + } while (1); to_free = calc_csum_metadata_size(inode, num_bytes); if (nr_extents > 0) |