Btrfs: proper -ENOSPC handling

At the start of a transaction we do a btrfs_reserve_metadata_space() and
specify how many items we plan on modifying.  Then once we've done our
modifications and such, just call btrfs_unreserve_metadata_space() for
the same number of items we reserved.

For keeping track of metadata needed for data I've had to add an extent_io op
for when we merge extents.  This lets us track space properly when we are doing
sequential writes, so we don't end up reserving way more metadata space than
what we need.

The only place where the metadata space accounting is not done is in the
relocation code.  This is because Yan is going to be reworking that code in the
near future, so running btrfs-vol -b could still possibly result in a ENOSPC
related panic.  This patch also turns off the metadata_ratio stuff in order to
allow users to more efficiently use their disk space.

This patch makes it so we track how much metadata we need for an inode's
delayed allocation extents by tracking how many extents are currently
waiting for allocation.  It introduces two new callbacks for the
extent_io tree's, merge_extent_hook and split_extent_hook.  These help
us keep track of when we merge delalloc extents together and split them
up.  Reservations are handled prior to any actually dirty'ing occurs,
and then we unreserve after we dirty.

btrfs_unreserve_metadata_for_delalloc() will make the appropriate
unreservations as needed based on the number of reservations we
currently have and the number of extents we currently have.  Doing the
reservation outside of doing any of the actual dirty'ing lets us do
things like filemap_flush() the inode to try and force delalloc to
happen, or as a last resort actually start allocation on all delalloc
inodes in the fs.  This has survived dbench, fs_mark and an fsx torture
test.

Signed-off-by: Josef Bacik <jbacik@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 193 insertions, 31 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 01c5f8b5a34e..3cc5677f5440 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1159,6 +1159,83 @@ static int run_delalloc_range(struct inode *inode, struct page *locked_page,
         return ret;
 }
 
+static int btrfs_split_extent_hook(struct inode *inode,
+                                    struct extent_state *orig, u64 split)
+{
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        u64 size;
+
+        if (!(orig->state & EXTENT_DELALLOC))
+                return 0;
+
+        size = orig->end - orig->start + 1;
+        if (size > root->fs_info->max_extent) {
+                u64 num_extents;
+                u64 new_size;
+
+                new_size = orig->end - split + 1;
+                num_extents = div64_u64(size + root->fs_info->max_extent - 1,
+                                        root->fs_info->max_extent);
+
+                /*
+                 * if we break a large extent up then leave delalloc_extents be,
+                 * since we've already accounted for the large extent.
+                 */
+                if (div64_u64(new_size + root->fs_info->max_extent - 1,
+                              root->fs_info->max_extent) < num_extents)
+                        return 0;
+        }
+
+        BTRFS_I(inode)->delalloc_extents++;
+
+        return 0;
+}
+
+/*
+ * extent_io.c merge_extent_hook, used to track merged delayed allocation
+ * extents so we can keep track of new extents that are just merged onto old
+ * extents, such as when we are doing sequential writes, so we can properly
+ * account for the metadata space we'll need.
+ */
+static int btrfs_merge_extent_hook(struct inode *inode,
+                                   struct extent_state *new,
+                                   struct extent_state *other)
+{
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        u64 new_size, old_size;
+        u64 num_extents;
+
+        /* not delalloc, ignore it */
+        if (!(other->state & EXTENT_DELALLOC))
+                return 0;
+
+        old_size = other->end - other->start + 1;
+        if (new->start < other->start)
+                new_size = other->end - new->start + 1;
+        else
+                new_size = new->end - other->start + 1;
+
+        /* we're not bigger than the max, unreserve the space and go */
+        if (new_size <= root->fs_info->max_extent) {
+                BTRFS_I(inode)->delalloc_extents--;
+                return 0;
+        }
+
+        /*
+         * If we grew by another max_extent, just return, we want to keep that
+         * reserved amount.
+         */
+        num_extents = div64_u64(old_size + root->fs_info->max_extent - 1,
+                                root->fs_info->max_extent);
+        if (div64_u64(new_size + root->fs_info->max_extent - 1,
+                      root->fs_info->max_extent) > num_extents)
+                return 0;
+
+        BTRFS_I(inode)->delalloc_extents--;
+
+        return 0;
+}
+
 /*
  * extent_io.c set_bit_hook, used to track delayed allocation
  * bytes in this file, and to maintain the list of inodes that
@@ -1167,6 +1244,7 @@ static int run_delalloc_range(struct inode *inode, struct page *locked_page,
 static int btrfs_set_bit_hook(struct inode *inode, u64 start, u64 end,
                        unsigned long old, unsigned long bits)
 {
+
         /*
          * set_bit and clear bit hooks normally require _irqsave/restore
          * but in this case, we are only testeing for the DELALLOC
@@ -1174,6 +1252,8 @@ static int btrfs_set_bit_hook(struct inode *inode, u64 start, u64 end,
          */
         if (!(old & EXTENT_DELALLOC) && (bits & EXTENT_DELALLOC)) {
                 struct btrfs_root *root = BTRFS_I(inode)->root;
+
+                BTRFS_I(inode)->delalloc_extents++;
                 btrfs_delalloc_reserve_space(root, inode, end - start + 1);
                 spin_lock(&root->fs_info->delalloc_lock);
                 BTRFS_I(inode)->delalloc_bytes += end - start + 1;
@@ -1190,22 +1270,27 @@ static int btrfs_set_bit_hook(struct inode *inode, u64 start, u64 end,
 /*
  * extent_io.c clear_bit_hook, see set_bit_hook for why
  */
-static int btrfs_clear_bit_hook(struct inode *inode, u64 start, u64 end,
-                         unsigned long old, unsigned long bits)
+static int btrfs_clear_bit_hook(struct inode *inode,
+                                struct extent_state *state, unsigned long bits)
 {
         /*
          * set_bit and clear bit hooks normally require _irqsave/restore
          * but in this case, we are only testeing for the DELALLOC
          * bit, which is only set or cleared with irqs on
          */
-        if ((old & EXTENT_DELALLOC) && (bits & EXTENT_DELALLOC)) {
+        if ((state->state & EXTENT_DELALLOC) && (bits & EXTENT_DELALLOC)) {
                 struct btrfs_root *root = BTRFS_I(inode)->root;
 
+                BTRFS_I(inode)->delalloc_extents--;
+                btrfs_unreserve_metadata_for_delalloc(root, inode, 1);
+
                 spin_lock(&root->fs_info->delalloc_lock);
-                if (end - start + 1 > root->fs_info->delalloc_bytes) {
+                if (state->end - state->start + 1 >
+                    root->fs_info->delalloc_bytes) {
                         printk(KERN_INFO "btrfs warning: delalloc account "
                                "%llu %llu\n",
-                               (unsigned long long)end - start + 1,
+                               (unsigned long long)
+                               state->end - state->start + 1,
                                (unsigned long long)
                                root->fs_info->delalloc_bytes);
                         btrfs_delalloc_free_space(root, inode, (u64)-1);
@@ -1213,9 +1298,12 @@ static int btrfs_clear_bit_hook(struct inode *inode, u64 start, u64 end,
                         BTRFS_I(inode)->delalloc_bytes = 0;
                 } else {
                         btrfs_delalloc_free_space(root, inode,
-                                                  end - start + 1);
-                        root->fs_info->delalloc_bytes -= end - start + 1;
-                        BTRFS_I(inode)->delalloc_bytes -= end - start + 1;
+                                                  state->end -
+                                                  state->start + 1);
+                        root->fs_info->delalloc_bytes -= state->end -
+                                state->start + 1;
+                        BTRFS_I(inode)->delalloc_bytes -= state->end -
+                                state->start + 1;
                 }
                 if (BTRFS_I(inode)->delalloc_bytes == 0 &&
                     !list_empty(&BTRFS_I(inode)->delalloc_inodes)) {
@@ -2950,7 +3038,12 @@ again:
                 goto again;
         }
 
-        btrfs_set_extent_delalloc(inode, page_start, page_end);
+        ret = btrfs_set_extent_delalloc(inode, page_start, page_end);
+        if (ret) {
+                unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
+                goto out_unlock;
+        }
+
         ret = 0;
         if (offset != PAGE_CACHE_SIZE) {
                 kaddr = kmap(page);
@@ -2981,15 +3074,11 @@ int btrfs_cont_expand(struct inode *inode, loff_t size)
         u64 last_byte;
         u64 cur_offset;
         u64 hole_size;
-        int err;
+        int err = 0;
 
         if (size <= hole_start)
                 return 0;
 
-        err = btrfs_check_metadata_free_space(root);
-        if (err)
-                return err;
-
         btrfs_truncate_page(inode->i_mapping, inode->i_size);
 
         while (1) {
@@ -3024,12 +3113,18 @@ int btrfs_cont_expand(struct inode *inode, loff_t size)
                                                  cur_offset, &hint_byte, 1);
                         if (err)
                                 break;
+
+                        err = btrfs_reserve_metadata_space(root, 1);
+                        if (err)
+                                break;
+
                         err = btrfs_insert_file_extent(trans, root,
                                         inode->i_ino, cur_offset, 0,
                                         0, hole_size, 0, hole_size,
                                         0, 0, 0);
                         btrfs_drop_extent_cache(inode, hole_start,
                                         last_byte - 1, 0);
+                        btrfs_unreserve_metadata_space(root, 1);
                 }
                 free_extent_map(em);
                 cur_offset = last_byte;
@@ -3990,11 +4085,18 @@ static int btrfs_mknod(struct inode *dir, struct dentry *dentry,
         if (!new_valid_dev(rdev))
                 return -EINVAL;
 
-        err = btrfs_check_metadata_free_space(root);
+        /*
+         * 2 for inode item and ref
+         * 2 for dir items
+         * 1 for xattr if selinux is on
+         */
+        err = btrfs_reserve_metadata_space(root, 5);
         if (err)
-                goto fail;
+                return err;
 
         trans = btrfs_start_transaction(root, 1);
+        if (!trans)
+                goto fail;
         btrfs_set_trans_block_group(trans, dir);
 
         err = btrfs_find_free_objectid(trans, root, dir->i_ino, &objectid);
@@ -4032,6 +4134,7 @@ out_unlock:
         nr = trans->blocks_used;
         btrfs_end_transaction_throttle(trans, root);
 fail:
+        btrfs_unreserve_metadata_space(root, 5);
         if (drop_inode) {
                 inode_dec_link_count(inode);
                 iput(inode);
@@ -4052,10 +4155,18 @@ static int btrfs_create(struct inode *dir, struct dentry *dentry,
         u64 objectid;
         u64 index = 0;
 
-        err = btrfs_check_metadata_free_space(root);
+        /*
+         * 2 for inode item and ref
+         * 2 for dir items
+         * 1 for xattr if selinux is on
+         */
+        err = btrfs_reserve_metadata_space(root, 5);
         if (err)
-                goto fail;
+                return err;
+
         trans = btrfs_start_transaction(root, 1);
+        if (!trans)
+                goto fail;
         btrfs_set_trans_block_group(trans, dir);
 
         err = btrfs_find_free_objectid(trans, root, dir->i_ino, &objectid);
@@ -4096,6 +4207,7 @@ out_unlock:
         nr = trans->blocks_used;
         btrfs_end_transaction_throttle(trans, root);
 fail:
+        btrfs_unreserve_metadata_space(root, 5);
         if (drop_inode) {
                 inode_dec_link_count(inode);
                 iput(inode);
@@ -4118,10 +4230,16 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
         if (inode->i_nlink == 0)
                 return -ENOENT;
 
-        btrfs_inc_nlink(inode);
-        err = btrfs_check_metadata_free_space(root);
+        /*
+         * 1 item for inode ref
+         * 2 items for dir items
+         */
+        err = btrfs_reserve_metadata_space(root, 3);
         if (err)
-                goto fail;
+                return err;
+
+        btrfs_inc_nlink(inode);
+
         err = btrfs_set_inode_index(dir, &index);
         if (err)
                 goto fail;
@@ -4145,6 +4263,7 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
         nr = trans->blocks_used;
         btrfs_end_transaction_throttle(trans, root);
 fail:
+        btrfs_unreserve_metadata_space(root, 3);
         if (drop_inode) {
                 inode_dec_link_count(inode);
                 iput(inode);
@@ -4164,17 +4283,21 @@ static int btrfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
         u64 index = 0;
         unsigned long nr = 1;
 
-        err = btrfs_check_metadata_free_space(root);
+        /*
+         * 2 items for inode and ref
+         * 2 items for dir items
+         * 1 for xattr if selinux is on
+         */
+        err = btrfs_reserve_metadata_space(root, 5);
         if (err)
-                goto out_unlock;
+                return err;
 
         trans = btrfs_start_transaction(root, 1);
-        btrfs_set_trans_block_group(trans, dir);
-
-        if (IS_ERR(trans)) {
-                err = PTR_ERR(trans);
+        if (!trans) {
+                err = -ENOMEM;
                 goto out_unlock;
         }
+        btrfs_set_trans_block_group(trans, dir);
 
         err = btrfs_find_free_objectid(trans, root, dir->i_ino, &objectid);
         if (err) {
@@ -4223,6 +4346,7 @@ out_fail:
         btrfs_end_transaction_throttle(trans, root);
 
 out_unlock:
+        btrfs_unreserve_metadata_space(root, 5);
         if (drop_on_err)
                 iput(inode);
         btrfs_btree_balance_dirty(root, nr);
@@ -4747,6 +4871,13 @@ int btrfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
                 goto out;
         }
 
+        ret = btrfs_reserve_metadata_for_delalloc(root, inode, 1);
+        if (ret) {
+                btrfs_free_reserved_data_space(root, inode, PAGE_CACHE_SIZE);
+                ret = VM_FAULT_SIGBUS;
+                goto out;
+        }
+
         ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */
 again:
         lock_page(page);
@@ -4778,7 +4909,12 @@ again:
                 goto again;
         }
 
-        btrfs_set_extent_delalloc(inode, page_start, page_end);
+        ret = btrfs_set_extent_delalloc(inode, page_start, page_end);
+        if (ret) {
+                unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
+                ret = VM_FAULT_SIGBUS;
+                goto out_unlock;
+        }
         ret = 0;
 
         /* page is wholly or partially inside EOF */
@@ -4801,6 +4937,7 @@ again:
         unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
 
 out_unlock:
+        btrfs_unreserve_metadata_for_delalloc(root, inode, 1);
         if (!ret)
                 return VM_FAULT_LOCKED;
         unlock_page(page);
@@ -4917,6 +5054,8 @@ struct inode *btrfs_alloc_inode(struct super_block *sb)
                 return NULL;
         ei->last_trans = 0;
         ei->logged_trans = 0;
+        ei->delalloc_extents = 0;
+        ei->delalloc_reserved_extents = 0;
         btrfs_ordered_inode_tree_init(&ei->ordered_tree);
         INIT_LIST_HEAD(&ei->i_orphan);
         INIT_LIST_HEAD(&ei->ordered_operations);
@@ -5070,7 +5209,12 @@ static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry,
             new_inode->i_size > BTRFS_EMPTY_DIR_SIZE)
                 return -ENOTEMPTY;
 
-        ret = btrfs_check_metadata_free_space(root);
+        /*
+         * 2 items for dir items
+         * 1 item for orphan entry
+         * 1 item for ref
+         */
+        ret = btrfs_reserve_metadata_space(root, 4);
         if (ret)
                 return ret;
 
@@ -5185,6 +5329,8 @@ out_fail:
 
         if (old_inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
                 up_read(&root->fs_info->subvol_sem);
+
+        btrfs_unreserve_metadata_space(root, 4);
         return ret;
 }
 
@@ -5256,11 +5402,18 @@ static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
         if (name_len > BTRFS_MAX_INLINE_DATA_SIZE(root))
                 return -ENAMETOOLONG;
 
-        err = btrfs_check_metadata_free_space(root);
+        /*
+         * 2 items for inode item and ref
+         * 2 items for dir items
+         * 1 item for xattr if selinux is on
+         */
+        err = btrfs_reserve_metadata_space(root, 5);
         if (err)
-                goto out_fail;
+                return err;
 
         trans = btrfs_start_transaction(root, 1);
+        if (!trans)
+                goto out_fail;
         btrfs_set_trans_block_group(trans, dir);
 
         err = btrfs_find_free_objectid(trans, root, dir->i_ino, &objectid);
@@ -5341,6 +5494,7 @@ out_unlock:
         nr = trans->blocks_used;
         btrfs_end_transaction_throttle(trans, root);
 out_fail:
+        btrfs_unreserve_metadata_space(root, 5);
         if (drop_inode) {
                 inode_dec_link_count(inode);
                 iput(inode);
@@ -5362,6 +5516,11 @@ static int prealloc_file_range(struct btrfs_trans_handle *trans,
 
         while (num_bytes > 0) {
                 alloc_size = min(num_bytes, root->fs_info->max_extent);
+
+                ret = btrfs_reserve_metadata_space(root, 1);
+                if (ret)
+                        goto out;
+
                 ret = btrfs_reserve_extent(trans, root, alloc_size,
                                            root->sectorsize, 0, alloc_hint,
                                            (u64)-1, &ins, 1);
@@ -5381,6 +5540,7 @@ static int prealloc_file_range(struct btrfs_trans_handle *trans,
                 num_bytes -= ins.offset;
                 cur_offset += ins.offset;
                 alloc_hint = ins.objectid + ins.offset;
+                btrfs_unreserve_metadata_space(root, 1);
         }
 out:
         if (cur_offset > start) {
@@ -5566,6 +5726,8 @@ static struct extent_io_ops btrfs_extent_io_ops = {
         .readpage_io_failed_hook = btrfs_io_failed_hook,
         .set_bit_hook = btrfs_set_bit_hook,
         .clear_bit_hook = btrfs_clear_bit_hook,
+        .merge_extent_hook = btrfs_merge_extent_hook,
+        .split_extent_hook = btrfs_split_extent_hook,
 };
 
 /*