PCf
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PC1)
`wo 91/03024
`
`WORLD JNTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`
`(51) Internatil\nal Patent Classification 5 :
`
`(11) International Publication Number:
`
`G06F 15/403, 15/40
`
`( 43) International Publication Date:
`
`7 March 1991 (07.03.91)
`
`·'
`
`(21) International Application Number:
`
`PCT/US90/04570
`
`(22) International Filing Date:
`
`14 August 1990 (14.08.90)
`
`(30) Priority data:
`394,324
`
`us
`(71)Applicant: MICROSOFT CORPORATION [US/US];
`One Microsoft Way, Redmond, WA 98052-6399 (US).
`
`14 August 1989 (14.08.89)
`
`; 14504 N.E. 77th
`(72)Inventors: MASDEN, Kenneth, E.
`Street, Redmond, WA 98052 (US). SMIRL, John, D. ;
`8215 N.E. 115th Place, Kirkland, WA 98034 (US).
`KING, John, W. ; 1942 3rd Street, Kirkland, WA 98033
`(US). RUBIN, Darryl, E. ; 17707 N.E. 14lst St., Red(cid:173)
`mond, WA 98052 (US).
`
`(74) Agents: JACOBSON, James, E., Jr. et al.; Seed and Berry,
`6300 Columbia Center, Seattle, WA 98104-7092 (US).
`
`(81) Designated States: AT (European patent), AU, BB, BE
`(European patent), BF (OAPI patent), BG, BJ (OAPI
`patent), BR, CA, CF (OAPI patent), CG (OAPI patent),
`CH (European patent), CM (OAPI patent), DE (Euro(cid:173)
`pean patent)*, DK (European patent), ES (European pa(cid:173)
`tent), Fl, FR (European patent), GA (OAPI patent), GB
`(European patent), HU, IT (European patent), JP, KR,
`LK, LU (European patent), MC, MG, ML (OAPI pa(cid:173)
`tent), MR (OAPI patent), MW, NL (European patent),
`NO, RO, SD, SE (European patent), SN (OAPI patent),
`SU, TD (OAPI patent), TG (OAPI patent).
`
`Published
`With international search report.
`Before the expiration of the time limit for amending the
`claims and to be republished in the event of the receipt of
`amendmen/s.
`
`(54) Title: METHOD AND SYSTEM FOR OPPORTUNISTIC LOCKING IN A NETWORKED COMPUTER SYSTEM
`
`(57) Abstract
`
`The present invention contemplates a method and means for im-
`proving the performance of distributed computer systems including a
`file server and a plurality of remote workstations. In operation, a re(cid:173)
`quest is issued from one of the remote workstations to open a file or re(cid:173)
`1
`. cord resident on the file server in a sharing mode. The system of the
`present invention automatically converts the sharing mode request into
`a request to open the file or record in an opportunistic locked exclusive
`mode. The file server then determines whether the requested file or re(cid:173)
`cord has been opened by another workstation. If the file or record is
`not currently open, the file or record is opened in the opportunistic
`locked exclusive mode and the file or record is processed and cached
`locally in a system workstation. If the file or record is already open, the
`file is opened in the conventional sharing mode. If the file or record
`opened in the opportunistic locked exclusive mode is requested by an(cid:173)
`other client, the locally cached data is written to the file server and the
`system reverts to the conventional sharing mode. The system of the
`present invention is also compatible with conventional exclusive mode
`operation which may be manually requested by a client.
`
`* See back of page
`
`LG Electronics, Inc. et at.
`EXHIBIT 1013
`IPR Petition for
`U.S. Patent No. 7,149,511
`
`

`
`DESIGNATIONS OF "DE"
`
`Until further notice, any designation of "DE" in any international application
`whose international filing date is prior to October 3, 1990, shall have effect in the
`territory of the Federal Republic of Germany with the exception of the territory of the
`former German Democratic Republic.
`
`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCf on the front pages of pamphlets publishing international
`·
`applications under the PCf.
`
`AT
`AU
`BB
`BE
`BF
`BG
`BJ
`BR
`CA
`CF
`CG
`CH
`CM
`DE
`DK
`
`Austria
`Australia
`Barbados
`Belgium
`Burkina Fasso
`Bulgaria
`Benin
`Brazil
`Canada
`Central African Republic
`Congo
`Swita:rland
`Cameroon
`Germany
`Denmark
`
`Spain
`ES
`Finland
`FI
`France
`FR
`GA Gabon
`GB
`United Kingdom
`GR Greece
`Hungary
`HU
`Italy
`IT
`Japan
`JP
`Democratic People's Republic
`KP
`of Korea
`Republic of Korea
`Liechtenstein
`Sri Lanka
`Luxembourg
`
`KR
`LI
`LK
`LU
`
`MC Monaco
`MG Madagascar
`ML Mali
`MR Mauritania
`MW Malawi
`NL
`Netherlands
`NO
`Norway
`PL
`Poland
`RO
`Romania
`so
`Sudan
`SE
`Sweden
`SN
`Senegal
`su
`Soviet Union
`TO
`Chad
`TG
`Togo
`us
`United States of America
`
`

`
`wo 91/03024
`
`PCT /US90/04570
`
`1
`
`Description
`
`METHOD AND SYSTEM FOR OPPORTUNISTIC LOCKING
`IN A NETWORKED COMPUTER SYSTEM
`
`5
`
`Field of the Invention
`field of
`the
`to
`relates
`This
`invention
`computer networks and, more specifically, to a method
`and means for improving the speed and performance of a
`10 networked computer system.
`
`15
`
`20
`
`Background of the Invention
`computer networks are a well-known computer
`architecture wherein users of the network are typically
`Computer networks
`located in many diverse locations.
`are adapted for use with independent computer systems,
`each having local file storage capability, as well as
`diskless terminal-type systems wherein master files are
`stored on a single file server.
`computer
`one popular use
`for distributed
`is database management.
`In
`a multiuser
`systems
`environment, it is
`important that all users of
`the
`database have access to current information as each user
`of
`the system is permitted to make changes
`to
`the
`25 database at will.
`Therefore, database
`files are
`typically resident on a single-system file server. When
`accessing
`a database with
`remote workstations,
`the
`remote workstations
`typically
`issue requests
`to
`the
`system file server to retrieve the desired information.
`30 As an entry in the file is updated or modified, the new
`information is sent from the workstation to the file
`server so that all 11 clients 11
`in the system have access
`to current
`information.
`For example,
`in mulituser
`database applications, many clients have access to all
`records in the da~abase. If a client reads and updates
`a record, and a second client reads the same record
`before the master file is updated, each client will have
`
`35
`
`

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`PCf /US90/04570
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`
`inconsistent versions of the same record. Most database
`applications include some provision to avoid the problem
`of inconsistent data. Typically, while operating in a
`sharing mode, a client issues a request to open and lock
`5 specified
`records
`in
`the database.
`The specified
`records are
`then read and modified.
`The modified
`records are
`then written to the master file on
`the
`server and the records are then unlocked and closed.
`While the records are locked, no other client has access
`~o to
`the
`record.
`While
`this
`technique prevents
`inconsistent data,
`the process of opening,
`locking,
`reading, writing,
`closing,
`and unlocking
`files or
`records may result in as many as eight messages across
`the computer network.
`In many computer networks, it is common for
`only a single user to be using the network at any one
`time and inconsistent data is not possible.
`In this
`situation,
`the process of opening,
`locking,
`reading,
`writing, unlocking, and closing files or records results
`in wasted time and increased system overhead.
`the above(cid:173)
`The present
`invention overcomes
`mentioned problem by allowing network workstations to
`automatically
`operate
`in
`an
`opportunistic
`locked
`exclusive mode when files are only used by single
`25 clients and by automatically switching to a conventional
`sharing mode when file data is required by multiple
`clients.
`In the opportunistic locked exclusive mode,
`files or records are processed and cached locally, thus
`eliminating
`a
`large portion of network messaging
`traffic.
`If another client requires access to the file,
`the locally cached data is written to the file server,
`and the system reverts to sharing mode operation.
`
`~5
`
`20
`
`30
`
`35
`
`Summary and Objects of the Invention
`In summa~y, the present invention contemplates
`a method and means for
`improving the performance of
`distributed computer systems including a file server and
`
`

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`
`3
`
`In operation, a
`a plurality of remote workstations.
`request is issued from one of the remote workstations to
`open a file or record resident on the file server in a
`sharing mode.
`The system of
`the present
`invention
`5 automatically converts the sharing mode request into a
`request to open the file or record in an opportunistic
`locked exclusive mode.
`The file server then determines
`whether the requested file or record has been opened by
`another workstation.
`If the file or record is not
`10 currently open,
`the file or record is opened in the
`opportunistic
`locked exclusive mode and
`the file or
`record is processed and cached
`locally
`in a
`system
`workstation.
`If the file or record is already open, the
`file is opened in the conventional sharing mode.
`If the
`15 file or
`record opened
`in
`the opportunistic
`locked
`exclusive mode
`is requested by another client,
`the
`locally cached data is written to the file server and
`the system reverts to the conventional sharing mode.
`The system of the present invention is also compatible
`20 with conventional exclusive mode operation which may be
`manually requested by a client.
`Accordingly, it is an object of the present
`invention to provide a method and means for improving
`the performance of a networked computer system.
`It is another object of the present invention
`to eliminate
`the
`system overhead of workstations
`operating in a sharing mode when file services are only
`required by a single workstation at a given point in
`time.
`
`25
`
`30
`
`It is another object of the present invention
`to provide
`a method
`and means
`for automatically
`switching workstations between an opportunistic locked
`exclusive mode and a sharing mode based on the number of
`users requiring access
`to files resident on a file
`e
`35 server.
`'
`
`It is another object of the present invention
`to provide opportunistic exclusive locked mode operation
`
`

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`4
`
`which is transparently available to application programs
`without modification of the application program.
`
`5
`
`10
`
`15
`
`Brief Description of the Drawings
`These
`and
`other
`objects may
`fully
`be
`understood through the detailed description below and
`the accompanying drawings in which:
`Figure 1 is a diagram of a typical local area
`network system.
`Figure 2 is a more detailed diagram of the
`system of Figure 1.
`the
`flow diagram detailing
`is a
`Figure 3
`operation of the file server of the present inven:tion
`when opening file server files.
`Figure 4 is a flow diagram which describes the
`operation of the workstations of the present invention
`when requesting a file to be opened in the OPlocked
`exclusive mode.
`Figure 5 is a flow diagram which describes the
`2 o operation of the workstations of the present invention
`when
`the OPlocked exclusive mode operation must be
`terminated.
`
`25
`
`Detailed Description of the Invention
`While the principles of the present invention
`may be applied to virtually any distributed computer
`system,
`the present invention is particularly adapted
`for use with local area network
`(LAN)
`systems of the
`type shown in Figure l.
`LAN systems are particularly
`30 adapted for multiuser applications, one example of which
`are database management systems.
`In the system 100, a
`file server 102 provides file services to a plurality of
`remote workstations 104, 106, 108 and 110. While the
`system 100
`is
`shown with
`four workstations,
`those
`It
`35 s~illed in the art will appreciate that LAN systems are
`adapted
`for
`use with virtually
`any
`number
`of
`workstations. Furthermore, the system 100 is shown with
`
`

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`PCf /US90/04570
`
`5
`
`each workstation directly coupled to the file server
`102. The present invention is adapted for use with all
`types of networked systems regardless of the method used
`to interface the file server and workstations.
`In the
`5 context of
`the present
`invention, users of
`the LAN
`system are referred to as clients and file services
`refers to various file management tasks such as opening,
`updating and closing files.
`In the context of the
`present invention, the terms "file" or "files" refers to
`10 any collection of information or data regardless of size
`or whether the information or data is merely a portion
`or subset of a larger collection of information or data.
`The principles of the present invention may be applied
`to
`any
`collection of
`information
`accessed
`in
`a
`15 distributed manner.
`A more detailed diagram of the system 100 is
`in Figure 2. While the present
`invention is
`shown
`described herein in the context of a LAN system,
`the
`principles of the present invention may be applied to
`any type of distributed computer system.
`The present
`invention is adapted to operate with many known LAN
`systems and the LAN system 100 is preferably modelled
`after the well known LAN architecture described in ISO
`specification
`ISO
`7498,
`entitled
`"Open
`Systems
`Interconnection - Basic Reference Model."
`LAN system
`principles are also described in a
`text:
`Tannebaum,
`"Computer Networks," Prentice-Hall, Inc., 1981, ISBN-0-
`13-165183-8. The LAN system principles described in the
`above-mentioned publications are well known to persons
`30 of ordinary skill in the art. Briefly, however,
`The
`file server 102 comprises a server process 202 which
`cooperates with a kernel 204 to receive, generate and
`process system requests.
`The kernel further cooperates
`with a mechanism 206 which provides storage for system
`•
`35 ~iles.
`The kernel 204 communicates with the network
`through a
`redirector 208 and a
`transport 210.
`The
`redirector 208 and transport 210 are responsible for
`
`20
`
`25
`
`

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`PCf /US90/04570
`
`6
`
`5
`
`monitoring message traffic on the LAN, for communicating
`LAN messages to the kernel 204 and server process 202,
`and for packaging and returning messages or data from
`the kernel 204 and server process 202 to the LAN.
`to LAN
`The
`file
`server
`102
`is coupled
`communication lines 2~2 through a LAN
`interface 2~4.
`The LAN
`interface converts
`the messages
`and data
`processed by the file server 102 into a form consistent
`with the communications protocol of the LAN network.
`10 one such LAN protocol is Ethernet.
`A plurality of
`workstations 104, 106, 110 are further coupled to LAN
`communication lines through LAN
`interface devices 216,
`218, and 220, respectively. Each respective workstation
`comprises a
`transport 222, a redirector 224, a kernel
`It is anticipated
`~5 226 and application programs 228.
`that each workstation used with
`the LAN
`system
`is
`capable of independent or local operations as well as
`being able to access and modify files resident on file
`server 102.
`are
`systems, workstations
`LAN
`In prior
`in a
`sharing mode wherein all files are
`operated
`maintained on a file server, and are accessible to all
`clients simultaneously, or in an exclusive mode wherein
`files, or portions thereof, are transferred from the
`file server to the workstation for local processing.
`In
`the sharing mode, workstations
`issue requests to the
`file server to open and lock files or records resident
`on
`the file server.
`The file server
`responds by
`verifying the transaction and sending the requested data
`30 back to the workstation.
`The data is then modified by
`the workstation and then immediately written back to the
`This is followed by an instruction from
`file server.
`the workstation
`to
`unlock
`and
`close
`the
`file.
`Therefore, in the sharing mode, every time a record is
`•
`35 mpdified by a workstation, as many as eight messages may
`be communicated between the workstation and the file
`server. This model is based on the assumption that many
`
`20
`
`25
`
`

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`PCf /US90/04570
`
`7
`
`workstations may be working with a single file at the
`same time and thus, all portions of the file must be
`maintained at a single
`location,
`i.e., the file
`is
`typically resident on
`the file server so
`that all
`5 clients in the system have access to the most recent
`modifications to file records. While individual records
`are being modified by clients,
`they are
`temporarily
`locked to prevent inconsistent data.
`systems,
`In
`the exclusive mode of prior
`10 clients may manually instruct the file server to open a
`file exclusively, and deny access to all other users.
`The file (or portions of the file) is then transferred
`to the workstation requesting the file where it remains
`until the client closes the file and returns it to the
`15 file server.
`While
`this eliminates
`the need
`for
`communicating with the file server while operating in
`the exclusive mode, no other client in the system has
`access to the file while in this mode. Therefore, file
`access is provided on a first come, first served basis
`and many important file service requests may be denied.
`While
`the present
`invention
`is disclosed
`as
`an
`improvement to operating systems, the principles of the
`present invention are equally applicable to cooperating
`application systems.
`Furthermore, since
`the present
`invention may be incorporated in an operating system,
`existing applications may employ the present invention
`without modification of the application.
`In most LAN networks, the probability that a
`file is being modified only by a single user is quite
`30 high, but multiuser application problems must be written
`to assume multiple users. Therefore, the communication
`between a single workstation and the file server when
`operating in the sharing mode results in wasted time and
`increased system overhead. However, if a client opens a
`•
`35 f~le in
`the exclusive mode,
`important file service
`requests from other clients may be denied. The present
`invention
`overcomes
`this
`problem
`by
`providing
`
`20
`
`25
`
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`wo 91/03024
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`
`8
`
`25
`
`three
`in
`to operate
`workstations which are adapted
`an opportunistic
`locked {OPlocked) exclusive
`modes:
`mode, a sharing mode and a conventional exclusive mode.
`For the purpose of simplifying the explanation of the
`5 operation of
`the present
`invention,
`the explanation
`herein refers to the transfer of files. Those skilled
`in the art will appreciate that complete files are
`rarely
`transferred
`and
`in most applications, only
`portions of files are actually transferred between the
`10 file server and the associated workstations.
`As in prior systems, in the sharing mode it is
`assumed that a plurality of users may be modifying
`records in a single file simultaneously and the master
`file is not moved from the file server. In the OPlocked
`15 exclusive mode of the present invention, a single file
`(or
`a portion
`thereof) may
`be
`transferred
`to
`a
`workstation to be processed and cached locally and the
`file is automatically OPlocked.
`is
`When
`the user
`the updated file is
`completed with
`the file,
`then
`2 o returned to
`the file server.
`However,
`if another
`workstation requests file services on an Oplocked file,
`the file server sends a message to the workstation
`currently owning the file to return the updated file to
`the file server and to revert to a sharing mode.
`The present invention eliminates the problem
`of denying access to locked files while providing the
`advantages of exclusive mode operation by allowing
`automatic exclusive mode operation as long as no other
`clients require file services for that file.
`In yet
`3 o another aspect of
`the present
`invention, when
`a
`workstation requests sharing mode file services for a
`file, a sharing mode request is converted into a request
`for operation in the Oplocked exclusive mode.
`The file
`server then determines whether the file is
`currently
`open.
`If not, the file server opens the file in the
`Oplocked
`exclusive mode,
`even
`if exclusive mode
`operation is not requested by the client Application.
`
`35
`
`~
`
`..
`
`

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`wo 91/03024
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`9
`
`to
`Therefore, file services are efficiently provided
`clients in a manner which is totally transparent to the
`client.
`The present
`invention is totally compatible
`with
`the manual exclusive mode operation of prior
`systems. While the present invention is illustrated as
`a modification to workstation and file server operating
`systems, those skilled in the art will appreciate that
`the present invention could also be implemented within
`cooperating application programs.
`The
`following
`pseudo-code
`operation of the present invention.
`
`describes
`
`the
`
`5
`
`10
`
`Workstation:
`
`15 If file open request is for sharing_mode then
`send server request for open with OPlock
`else (open is for exclusive mode)
`send server a normal open request
`OPlock does not apply
`
`20
`
`25
`
`30
`
`35
`
`the server returns the open request the server
`When
`indicates if the file has been Oplocked.
`
`If the file was not Oplocked then
`proceed as normal for a sharing mode open
`else (the file is Oplocked)
`Treat the file as an exclusive open.
`
`The workstation can perform:
`
`(a) read ahead, write behind, lock caching, etc.
`(b) Any operation that could previously only be
`used by an exclusive open
`is used on an Oplocked
`exclusive open.
`
`While the file is Oplocked,
`the server may
`dynamically disallow
`the Oplocked
`status
`if
`file
`
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`
`services are requested by another workstation. This is
`done by sending a break_oplock message from the server
`to the workstation that has the file Oplocked.
`
`5
`
`When a break_oplock message is received:
`
`If the workstation has the file open:
`
`10
`
`15
`
`20
`
`25
`
`a) flush any write_behind data to the server
`b) flush any cached locks to the server
`c) invalidate any read ahead data
`d) send an oplock_broken message to the server
`
`the file open.
`The workstation still has
`However, the workstation can't use any of the buffering
`(read ahead, etc) until
`the workstation
`algorithms
`reverts to an Oplocked mode.
`If the workstation receives a break_oplock
`message for a file that is not opened, it is assumed
`that the workstation's close of the file crossed the
`break_oplock message on the communication lines and the
`break_oplock message is ignored.
`
`Server:
`
`When
`request:
`
`the server
`
`receives an open with OPlock
`
`1) if this is the first client opening the file,
`the OPlock request is granted.
`
`30
`
`2) if this is the second client requesting an open
`of the file, and the first client has the file Oplocked,
`the file server sends a break OPlock message to the
`35 ~orkstation holding the Oplocked file. This workstation
`then sends any write_behind data and any cached locks to
`the server. This data is followed by an oplock_broken
`
`~
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`11
`
`message. After the oplock_broken message is received by
`the server, the server sends the second client an open
`but not Oplocked response.
`
`is not
`the OPlock
`The workstation holding
`required to respond with a break OPlock message. Instead
`the workstation may simply respond by closing the file.
`In this case the second client will now be the only
`opener and will receive the OPlock.
`
`5
`
`10
`
`3) If any other opens are received while a break
`OPlock is in progress, these open requests are queued
`until the break OPlock operation is complete. At this
`time they will be processed as normal though steps 1 and
`15 2 . The result will be sending opened but not Oplocked
`responses to any open that was pending.
`
`where:
`
`20
`
`read ahead data: In accordance with the principles of
`the present
`invention,
`if
`a client
`requests,
`for
`example, ten bytes of data, a workstation local buffer
`is set up, i.e., 4K in size, and 4K of data is read into
`the
`local buffer.
`The buffer
`is set up
`in
`the
`25 workstation redirector with the expectation that the
`user will eventually need this data.
`The next time a
`request for the data is made, it can be handled locally
`without accessing the file server. This is used in the
`exclusive mode and the Oplocked exclusive mode.
`
`30
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`35
`
`write behind data: In accordance with the principles of
`the present invention, if the client writes or saves
`small amounts of data it is stored in a workstation
`local buffer until buffer is full. Once the buffer is
`f,illed, the data fs transmitted to the server. This is
`used in the exclusive mode and the Oplocked exclusive
`mode.
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`invention
`The system of the present
`lock caching:
`tracks locks placed on a file locally.
`If it is known
`that a file is OPlocked, the request is not sent to the
`5 file server.
`If in the sharing mode, the locked bytes
`are sent to the file server. When in the sharing mode
`an application may make a call to lock certain bytes
`in the
`while they are being modified.
`For example,
`sharing mode,
`locked requests are sent to the file
`10 server to get certain records to modify.
`Once
`the
`records are modified, the records are send back to the
`file server with an unlock request.
`File lock and
`unlock requests are a feature of the well known MS-DOS
`operating
`system as well as many other operating
`systems.
`
`15
`
`locks that are present locally in a
`locks:
`cached
`workstation
`and haven't been sent to the file server.
`In other words, the client believes the locked range is
`locked.
`
`20
`
`The OPlocking process of the present invention
`is further described in conjunction with Figures 3 - 5.
`Figure 3 is a flow diagram of the operation of the file
`25 server portion of the system operating in accordance
`with the principles of the present invention. As will
`be discussed below, the present invention is adapted for
`use with
`the Server Message Block
`{SMB)
`protocol
`developed by Microsoft, Intel and IBM. For the purposes
`3 0 of the discussion below, SMBs refer to message packets
`sent between the server and workstations over the LAN
`communication lines. The process 300 is invoked when an
`open file SMB is received from a system workstation as
`indicated by item 302.
`The open file SMB
`includes a
`35 r~quest to open th~ file in the OPlocked exclusive mode.
`Control then passes to decision 304 to determine whether
`the requested file has already been opened by another
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`If not, item 306 is invoked to generate an
`the file open
`request
`in a exclusive
`
`workstation.
`SMB granting
`OPlocked mode.
`a desired
`include
`typically
`requests
`SMB
`5 operation such as open, as well as another operation
`such as a request to read a designated block of data.
`For example, an SMB request may be a request to open and
`read, open and write, read and
`lock, etc.
`The SMB
`message returned then returns the SMB instruction along
`10 with
`the file handle and
`the requested data.
`The
`present invention is directed primarily to the opening
`and closing of files and the mode in which files are
`opened. Therefore, the additional information contained
`in an SMB packet is not further discussed herein. Once
`a return SMB is generated in item 3 06, the SMB is sent
`to the requesting workstation via the LAN communication
`lines.
`If the requested file is currently open, control
`passes to decision 308 to determine whether the open
`file is OPlocked.
`If not, control is passed to item 318
`to generate a "grant normal open" SMB.
`If decision 308
`determines the file is OPlocked, control is passed to
`decision
`309
`to determine whether
`a
`break_oplock
`If so, control is passed to
`function is in process.
`item 317
`to wait until
`the break_oplock process
`is
`25 complete.
`Once complete, control passes to decision
`316,
`then to item 318 to generate a grant_normal_open
`SMB.
`If decision 309 determines a break_oplock function
`is not in process, control is passed to item 310 to
`generate and send a "break OPlock" SMB to the original
`file opener. Control then passes to item 312 to wait
`for a reply SMB.
`The reply SMB is received by item 314
`wherein the reply may consist of any combination of
`cached locks, write behind data or a close instruction.
`Control then passes to decision 316 to determine whether
`t,he SMB contained a file close instruction.
`If so,
`control returns to item 302.
`If not, control is passed
`to decision 304 described above.
`
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`Figure 4 is a flow diagram which describes the
`operation of the workstations of the present invention
`when requesting a file to be opened in the OPlocked
`exclusive mode.
`The routine 400 is invoked whenever a
`5 client requests operation in a sharing mode as indicated
`by item 402. Control then passes to item 404 wherein
`the workstation redirector converts this request to a
`request to open a file in the exclusive OPlocked mode,
`generates the appropriate SMB and sends the SMB to the
`10 file server via the LAN communication lines. Control
`then passes to item 406 wherein the workstation waits
`for a reply. Once a reply is received, control passes
`to item 407 to decode the SMB message from the server.
`Decision 408 then determines whether the OPlock request
`15 was granted.
`If not, control passes to item 410 wherein
`the file is open in a normal non-buffered mode. Control
`then passes to loop 412 which comprises item 414 and
`Item 414 is invoked to perform system I/O
`decision 416.
`until the file is closed.
`Decision 416 determines
`20 whether the file is closed.
`If decision 416 determines
`that the file is not closed, control loops back to item
`If decision 416 determines the file is closed,
`414.
`control passes to item 418 which indicates the file is
`closed.
`
`25
`
`30
`
`If decision 408 determines OPlock was granted,
`control passes to item 420 which indicates the file is
`open
`in the OPlocked exclusive mode.
`Control
`then
`passes to item 422 which allows buffered operations such
`as read ahead, write behind and lock caching. Loop 424
`is then invoked.
`Loop 424 comprises item 424, which
`performs buffered I/0 on
`the open file until it is
`closed. Decision 428 determines whether the file is
`closed.
`If decision 428 determines that the file is not
`closed, control loops back to item 422.
`If decision 428
`"
`35 qetermines the file is closed, control passes to item
`418, which indicates the file is closed. Note:
`loop
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`424 can be modified if an asynchronous break_oplock
`request (detailed in Figure 5) is received.
`Figure 5 is a flow diagram which describes the
`operation of the workstations of the present invention
`5 when
`the OPlocked exclusive mode operation must be
`terminated.
`The process
`500
`is
`invoked when
`a
`break_oplock SMB
`is received from the file server as
`indicated by
`item 502. Decision 504
`then determines
`the referenced file is open.
`whether
`If not,
`the
`in
`10 break_oplock SMB
`is
`ignored
`item 506.
`If the
`referenced file is open, control passes to
`item 508
`which transmits any write behind data and cached locks
`to the server and which invalidates any read ahead data.
`Control
`then passes
`to
`item 510 which
`transmits an
`15 oplock_broken SMB to the file server to indicate OPlock
`is broken and the workstation reverts to the sharing
`mode in item 512 by changing the file status to operate
`in a non-buffered I/O mode.
`Based on the description above, it will be
`2 o readily apparent to those of ordinary skill in the art
`that the present invention may be implemented with any
`of a number of well known LAN protocols. However, the
`present invention is particularly adapted for use with
`the Server Message Block
`(SMB)
`file sharing protocol.
`25 The SMB file sharing protocol is described in detail in
`a
`document
`"Microsoft Networks/OpenNET File Sharing
`Protocol," Intel part Number 138446, Microsoft corp.,
`1985,
`attached hereto as Appendix I, and a document
`"SMB File Sharing Protocol Extensions," Microsoft corp.,
`30 1988, attached hereto as Appendix II, both of which are
`incorporated herein by reference.
`References to the
`OPlocking
`technique of the present
`invention may be
`found in Appendix II, pp. 3, 4, 46-48 and 51-58.
`It
`should be noted that the references
`to
`the present
`35 i~vention is the document attached hereto as Appendix II
`were printed less than one year prior to the filing date
`of the present application.
`
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`
`In summary, a method and means for improving
`the performance of a distributed computer system has
`been described.
`In accordance with the principles of
`the present