linux/fs/fscache
David Howells b6e16652d6 fscache: Implement higher-level write I/O interface
Provide a higher-level function than fscache_write() to perform a write
from an inode's pagecache to the cache, whilst fending off concurrent
writes by means of the PG_fscache mark on a page:

	void fscache_write_to_cache(struct fscache_cookie *cookie,
				    struct address_space *mapping,
				    loff_t start,
				    size_t len,
				    loff_t i_size,
				    netfs_io_terminated_t term_func,
				    void *term_func_priv,
				    bool caching);

If caching is false, this function does nothing except call (*term_func)()
if given.  It assumes that, in such a case, PG_fscache will not have been
set on the pages.

Otherwise, if caching is true, this function requires the source pages to
have had PG_fscache set on them before calling.  start and len define the
region of the file to be modified and i_size indicates the new file size.
The source pages are extracted from the mapping.

term_func and term_func_priv work as for fscache_write().  The PG_fscache
marks will be cleared at the end of the operation, before term_func is
called or the function otherwise returns.

There is an additonal helper function to clear the PG_fscache bits from a
range of pages:

	void fscache_clear_page_bits(struct fscache_cookie *cookie,
				     struct address_space *mapping,
				     loff_t start, size_t len,
				     bool caching);

If caching is true, the pages to be managed are expected to be located on
mapping in the range defined by start and len.  If caching is false, it
does nothing.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819614155.215744.5528123235123721230.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906916346.143852.15632773570362489926.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967123599.1823006.12946816026724657428.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021522672.640689.4381958316198807813.stgit@warthog.procyon.org.uk/ # v4
2022-01-07 09:22:19 +00:00
..
cache.c fscache: Count data storage objects in a cache 2022-01-07 09:22:19 +00:00
cookie.c fscache: Implement cookie invalidation 2022-01-07 09:22:19 +00:00
internal.h fscache: Provide a means to begin an operation 2022-01-07 09:22:19 +00:00
io.c fscache: Implement higher-level write I/O interface 2022-01-07 09:22:19 +00:00
Kconfig fscache: Introduce new driver 2022-01-07 09:22:19 +00:00
main.c fscache: Implement cookie-level access helpers 2022-01-07 09:22:19 +00:00
Makefile fscache: Provide a means to begin an operation 2022-01-07 09:22:19 +00:00
proc.c fscache: Implement cookie registration 2022-01-07 09:22:19 +00:00
stats.c fscache: Provide read/write stat counters for the cache 2022-01-07 09:22:19 +00:00
volume.c fscache: Provide and use cache methods to lookup/create/free a volume 2022-01-07 09:22:19 +00:00