NAME
puffs_flush —
puffs kernel cache flushing and
invalidation routines
LIBRARY
library “libpuffs”
SYNOPSIS
#include
<puffs.h>
int
puffs_inval_namecache_dir(struct
puffs_usermount *pu, puffs_cookie_t cookie);
int
puffs_inval_namecache_all(struct
puffs_usermount *pu);
int
puffs_inval_pagecache_node(struct
puffs_usermount *pu, puffs_cookie_t cookie);
int
puffs_inval_pagecache_node_range(struct
puffs_usermount *pu, puffs_cookie_t cookie,
off_t start, off_t end);
int
puffs_flush_pagecache_node(struct
puffs_usermount *pu, puffs_cookie_t cookie);
int
puffs_flush_pagecache_node_range(struct
puffs_usermount *pu, puffs_cookie_t cookie,
off_t start, off_t end);
DESCRIPTION
These routines are used inform the kernel that any information it might have cached is no longer valid.puffs_inval_namecache_dir()
invalidates the name cache for a given directory. The argument
cookie should describe an existing and valid directory
cookie for the file system. Similarly,
puffs_inval_namecache_all()
invalidates the name cache for the entire file system (this routine might go
away).
The cached pages (file contents)
for a regular file described by cookie are invalidated
using
puffs_inval_pagecache_node().
A specific range can be invalidated using
puffs_inval_pagecache_node_range()
for a platform specific page level granularity. The offset
start will be
truncated
to a page boundary while end will be
rounded
up to the next page boundary. As a special case, specifying 0 as
end will invalidate all contents from
start to the end of the file.
It is especially important to note that these routines will not only invalidate data in the "read cache", but also data in the "write back" cache (conceptually speaking; in reality they are the same cache), which has not yet been flushed to the file server. Therefore any unflushed data will be lost.
The counterparts of the
invalidation routines are the flushing routines
puffs_flush_pagecache_node()
and
puffs_flush_pagecache_node_range(),
which force unwritten data from the kernel page cache to be written. For the
flush range version, the same range rules as with the invalidation routine
apply. The data is flushed asynchronously, i.e. if the routine returns
successfully, all the caller knows is that the data has been queued for
writing.