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authorChuck Lever <chuck.lever@oracle.com>2022-11-01 13:30:46 -0400
committerChuck Lever <chuck.lever@oracle.com>2022-11-28 12:54:45 -0500
commitb3276c1f5b268ff56622e9e125b792b4c3dc03ac (patch)
tree5ad5e7b3eb93854efb324a208ad83b33d82fb7bb /fs/nfsd/filecache.c
parent4d1ea8455716ca070e3cd85767e6f6a562a58b1b (diff)
NFSD: Flesh out a documenting comment for filecache.c
Record what we've learned recently about the NFSD filecache in a documenting comment so our future selves don't forget what all this is for. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Reviewed-by: Jeff Layton <jlayton@kernel.org>
Diffstat (limited to 'fs/nfsd/filecache.c')
-rw-r--r--fs/nfsd/filecache.c24
1 files changed, 24 insertions, 0 deletions
diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index cee44405cf7d..897dd47ffb0a 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -2,6 +2,30 @@
* Open file cache.
*
* (c) 2015 - Jeff Layton <jeff.layton@primarydata.com>
+ *
+ * An nfsd_file object is a per-file collection of open state that binds
+ * together:
+ * - a struct file *
+ * - a user credential
+ * - a network namespace
+ * - a read-ahead context
+ * - monitoring for writeback errors
+ *
+ * nfsd_file objects are reference-counted. Consumers acquire a new
+ * object via the nfsd_file_acquire API. They manage their interest in
+ * the acquired object, and hence the object's reference count, via
+ * nfsd_file_get and nfsd_file_put. There are two varieties of nfsd_file
+ * object:
+ *
+ * * non-garbage-collected: When a consumer wants to precisely control
+ * the lifetime of a file's open state, it acquires a non-garbage-
+ * collected nfsd_file. The final nfsd_file_put releases the open
+ * state immediately.
+ *
+ * * garbage-collected: When a consumer does not control the lifetime
+ * of open state, it acquires a garbage-collected nfsd_file. The
+ * final nfsd_file_put allows the open state to linger for a period
+ * during which it may be re-used.
*/
#include <linux/hash.h>