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NFSD: Flesh out a documenting comment for filecache.c

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[ Upstream commit b3276c1f5b268ff56622e9e125b792b4c3dc03ac ]

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>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Chuck Lever 2022-11-01 13:30:46 -04:00 committed by Greg Kroah-Hartman
parent 137d20da8e
commit e62d8c1281
1 changed files with 24 additions and 0 deletions
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24
fs/nfsd/filecache.c
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@ -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>