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authorMiklos Szeredi <miklos@szeredi.hu>2006-06-25 08:48:54 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-25 13:01:19 -0400
commita4d27e75ffb7b8ecb7eed0c7db0df975525f3fd7 (patch)
tree2353706a33196438547ed4651afd9f2d81dd96e8 /Documentation
parentf9a2842e5612b93fa20a624a8baa6c2a7ecea504 (diff)
[PATCH] fuse: add request interruption
Add synchronous request interruption. This is needed for file locking operations which have to be interruptible. However filesystem may implement interruptibility of other operations (e.g. like NFS 'intr' mount option). Signed-off-by: Miklos Szeredi <miklos@szeredi.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/fuse.txt48
1 files changed, 44 insertions, 4 deletions
diff --git a/Documentation/filesystems/fuse.txt b/Documentation/filesystems/fuse.txt
index 324df27704cc..a584f05403a4 100644
--- a/Documentation/filesystems/fuse.txt
+++ b/Documentation/filesystems/fuse.txt
@@ -124,6 +124,46 @@ For each connection the following files exist within this directory:
124 124
125Only the owner of the mount may read or write these files. 125Only the owner of the mount may read or write these files.
126 126
127Interrupting filesystem operations
128~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
129
130If a process issuing a FUSE filesystem request is interrupted, the
131following will happen:
132
133 1) If the request is not yet sent to userspace AND the signal is
134 fatal (SIGKILL or unhandled fatal signal), then the request is
135 dequeued and returns immediately.
136
137 2) If the request is not yet sent to userspace AND the signal is not
138 fatal, then an 'interrupted' flag is set for the request. When
139 the request has been successfully transfered to userspace and
140 this flag is set, an INTERRUPT request is queued.
141
142 3) If the request is already sent to userspace, then an INTERRUPT
143 request is queued.
144
145INTERRUPT requests take precedence over other requests, so the
146userspace filesystem will receive queued INTERRUPTs before any others.
147
148The userspace filesystem may ignore the INTERRUPT requests entirely,
149or may honor them by sending a reply to the _original_ request, with
150the error set to EINTR.
151
152It is also possible that there's a race between processing the
153original request and it's INTERRUPT request. There are two possibilities:
154
155 1) The INTERRUPT request is processed before the original request is
156 processed
157
158 2) The INTERRUPT request is processed after the original request has
159 been answered
160
161If the filesystem cannot find the original request, it should wait for
162some timeout and/or a number of new requests to arrive, after which it
163should reply to the INTERRUPT request with an EAGAIN error. In case
1641) the INTERRUPT request will be requeued. In case 2) the INTERRUPT
165reply will be ignored.
166
127Aborting a filesystem connection 167Aborting a filesystem connection
128~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 168~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
129 169
@@ -351,10 +391,10 @@ but is caused by a pagefault.
351 391
352Solution is basically the same as above. 392Solution is basically the same as above.
353 393
354An additional problem is that while the write buffer is being 394An additional problem is that while the write buffer is being copied
355copied to the request, the request must not be interrupted. This 395to the request, the request must not be interrupted/aborted. This is
356is because the destination address of the copy may not be valid 396because the destination address of the copy may not be valid after the
357after the request is interrupted. 397request has returned.
358 398
359This is solved with doing the copy atomically, and allowing abort 399This is solved with doing the copy atomically, and allowing abort
360while the page(s) belonging to the write buffer are faulted with 400while the page(s) belonging to the write buffer are faulted with