Providing multiple concurrent access to a file system
First Claim
1. A method for attempting to access a first data entity in a file system, the method being performed by a first computing entity, the file system also including one or more additional data entities that are concurrently accessible to at least one other computing entity, the method comprising:
- the first computing entity attempting to obtain a lease for itself on the first data entity without needing another computing entity acting on its behalf, by reading, using a processor, an owner field included in the file system that can be used to determine whether the first data entity is leased by a computing entity and a time field included in the file system that can be used to determine whether a lease for the first data entity has expired and;
if the owner field indicates that the first data entity is not currently leased, the first computing entity writing to the owner field in the file system to indicate an assumption of a lease of the first data entity and writing to the time field in the file system to indicate when the lease expires;
elseif the owner field indicates that the first data entity has been leased, the first computing entity reading the time field in the file system and;
if the time field indicates that the lease has expired, the first computing entity writing to the owner field in the file system to break the existing lease and to indicate an assumption of a new lease and the first computing entity writing to the time field in the file system to indicate when the new lease expires;
elseif the time field indicates that the lease is still active, concluding that the first data entity is currently unavailable; and
if a lease is obtained, the first computing entity accessing the first data entity while the lease is in effect.
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Accused Products
Abstract
Multiple computers are connected to a data storage unit that includes a file system, which further includes multiple data entities, including files, directories and the file system itself. The file system also includes, for each data entity, an owner field for indicating which computer, if any, has exclusive or shared access to the data entity, along with a time field for indicating when a lease of the data entity began. When a computer wants to lease a data entity, the computer uses a disk reservation capability to temporarily lock the data storage unit, and, if the data entity is not currently leased, the computer writes its own identification value into the owner field and a current time into the time field for the data entity, to claim the data entity for a renewable lease period. If a prior lease of a data entity has expired, another computer may break the lease and claim ownership for itself.
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Citations
25 Claims
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1. A method for attempting to access a first data entity in a file system, the method being performed by a first computing entity, the file system also including one or more additional data entities that are concurrently accessible to at least one other computing entity, the method comprising:
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the first computing entity attempting to obtain a lease for itself on the first data entity without needing another computing entity acting on its behalf, by reading, using a processor, an owner field included in the file system that can be used to determine whether the first data entity is leased by a computing entity and a time field included in the file system that can be used to determine whether a lease for the first data entity has expired and; if the owner field indicates that the first data entity is not currently leased, the first computing entity writing to the owner field in the file system to indicate an assumption of a lease of the first data entity and writing to the time field in the file system to indicate when the lease expires;
elseif the owner field indicates that the first data entity has been leased, the first computing entity reading the time field in the file system and; if the time field indicates that the lease has expired, the first computing entity writing to the owner field in the file system to break the existing lease and to indicate an assumption of a new lease and the first computing entity writing to the time field in the file system to indicate when the new lease expires;
elseif the time field indicates that the lease is still active, concluding that the first data entity is currently unavailable; and if a lease is obtained, the first computing entity accessing the first data entity while the lease is in effect. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for attempting to access a first data entity in a file system, the method being performed by a first computing entity, the file system also including one or more additional data entities that are concurrently accessible to at least one other computing entity, the method comprising:
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the first computing entity attempting to access the first data entity without needing another computing entity acting on its behalf, reading, using a processor, an owner field included in the file system that can be used to determine whether the first data entity is in use by a computing entity and determining whether the first data entity is in use by a computing entity; if the first data entity is not in use by a computing entity, the first computing entity writing to the owner field in the file system to take control of a lock on the first data entity; and if control of the lock is obtained, the first computing entity accessing the first data entity;
elseif control of the lock is not obtained, the first computing entity writing an entry to a queue owner field in the file system to indicate an interest in accessing the first data entity and waiting for an opportunity to access the first data entity. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification