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page cache: Rearrange address_space 

Change i_pages from a radix_tree_root to an xarray, convert the
documentation into kernel-doc format and change the order of the elements
to pack them better on 64-bit systems.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
This commit is contained in:
Matthew Wilcox 2018-03-05 22:46:03 -05:00
parent f32f004cdd
commit eb797a8ee0
1 changed files with 31 additions and 15 deletions
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46
include/linux/fs.h
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@ -403,24 +403,40 @@ int pagecache_write_end(struct file *, struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
struct page *page, void *fsdata);
/**
* struct address_space - Contents of a cacheable, mappable object.
* @host: Owner, either the inode or the block_device.
* @i_pages: Cached pages.
* @gfp_mask: Memory allocation flags to use for allocating pages.
* @i_mmap_writable: Number of VM_SHARED mappings.
* @i_mmap: Tree of private and shared mappings.
* @i_mmap_rwsem: Protects @i_mmap and @i_mmap_writable.
* @nrpages: Number of page entries, protected by the i_pages lock.
* @nrexceptional: Shadow or DAX entries, protected by the i_pages lock.
* @writeback_index: Writeback starts here.
* @a_ops: Methods.
* @flags: Error bits and flags (AS_*).
* @wb_err: The most recent error which has occurred.
* @private_lock: For use by the owner of the address_space.
* @private_list: For use by the owner of the address_space.
* @private_data: For use by the owner of the address_space.
*/
struct address_space {
struct inode *host; /* owner: inode, block_device */
struct radix_tree_root i_pages; /* cached pages */
atomic_t i_mmap_writable;/* count VM_SHARED mappings */
struct rb_root_cached i_mmap; /* tree of private and shared mappings */
struct rw_semaphore i_mmap_rwsem; /* protect tree, count, list */
/* Protected by the i_pages lock */
unsigned long nrpages; /* number of total pages */
/* number of shadow or DAX exceptional entries */
struct inode *host;
struct xarray i_pages;
gfp_t gfp_mask;
atomic_t i_mmap_writable;
struct rb_root_cached i_mmap;
struct rw_semaphore i_mmap_rwsem;
unsigned long nrpages;
unsigned long nrexceptional;
pgoff_t writeback_index;/* writeback starts here */
const struct address_space_operations *a_ops; /* methods */
unsigned long flags; /* error bits */
spinlock_t private_lock; /* for use by the address_space */
gfp_t gfp_mask; /* implicit gfp mask for allocations */
struct list_head private_list; /* for use by the address_space */
void *private_data; /* ditto */
pgoff_t writeback_index;
const struct address_space_operations *a_ops;
unsigned long flags;
errseq_t wb_err;
spinlock_t private_lock;
struct list_head private_list;
void *private_data;
} __attribute__((aligned(sizeof(long)))) __randomize_layout;
/*
* On most architectures that alignment is already the case; but