Make list elements paragraphs to increase spacing

blog/content/second-edition/posts/10-heap-allocation/index.md

@@ -434,9 +434,13 @@ The function takes mutable references to a [`Mapper`] and a [`FrameAllocator`] i
 The implementation can be broken down into two parts:
 
 - **Creating the page range:**: To create a range of the pages that we want to map, we convert the `HEAP_START` pointer to a [`VirtAddr`] type. Then we calculate the heap end address from it by adding the `HEAP_SIZE`. We want an inclusive bound (the address of the last byte of the heap), so we subtract 1. Next, we convert the addresses into [`Page`] types using the [`containing_address`] function. Finally, we create a page range from the start and end pages using the [`Page::range_inclusive`] function.
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 - **Mapping the pages:** The second step is to map all pages of the page range we just created. For that we iterate over the pages in that range using a `for` loop. For each page, we do the following:
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     - We allocate a physical frame that the page should be mapped to using the [`FrameAllocator::allocate_frame`] method. This method returns [`None`] when there are no more frames left. We deal with that case by mapping it to a [`MapToError::FrameAllocationFailed`] error through the [`Option::ok_or`] method and then apply the [question mark operator] to return early in the case of an error.
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     - We set the required `PRESENT` flag and the `WRITABLE` flag for the page. With these flags both read and write accesses are allowed, which makes sense for heap memory.
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     - We use the unsafe [`Mapper::map_to`] method for creating the mapping in the active page table. The method can fail, therefore we use the [question mark operator] again to forward the error to the caller. On success, the method returns a [`MapperFlush`] instance that we can use to update the [_translation lookaside buffer_] using the [`flush`] method.
 
 [`VirtAddr`]: https://docs.rs/x86_64/0.7.0/x86_64/struct.VirtAddr.html