Deduplicated data block ownership determination

1. A method of determining unique ownership of data blocks comprising:

selecting a first data block referenced by a first logical address of a first logical device, wherein first metadata for the first data block includes a reference count and a result and wherein the reference count denotes a number of references to the first data block and the result denotes a value used in determining sole unique ownership of the first data block;

determining C 1 , an expected value of the result of the first metadata when the first logical device is a sole unique owner of the first data block; and

performing first processing that determines whether the first logical device is the sole unique owner of the first data block, wherein the first processing includes:

determining whether C 1 equals a current value of the result of the first metadata; and

responsive to determining C 1 equals the current value of the result of the first metadata, determining that the first logical device is the sole unique owner of the first data block, and otherwise determining that the first logical device is not the sole unique owner of the first data block.

2. The method of claim 1 , wherein C 1 is determined using the reference count, a maximum prime number, a first prime number that is uniquely assigned to the first logical device.

3. The method of claim 2 , wherein the first logical device is one of a plurality of logical devices and each of the plurality of logical devices is assigned a different prime number less than the maximum prime number.

4. The method of claim 3 , further comprising:

writing first data to the first logical address of the first logical device; and

responsive to said writing, performing second processing including:

associating the first data block with the first logical address, wherein the first logical address references the first data block;

incrementing the reference count of the first metadata of the first data block; and updating the result of the first metadata from a first value to a second value, wherein said updating includes:

determining a first product by multiplying the first value by the first prime number that is assigned to the first logical device; and

determining the second value as the first value modulo the maximum prime number.

5. The method of claim 4 , wherein said second processing further comprises:

determining that the first data written to the first logical address is a duplicate of other data currently stored in the first data block; and

updating the first logical address to reference the first data block.

6. The method of claim 4 , wherein said second processing further comprises:

determining that the first data written to the first logical address is not a duplicate of other data currently stored;

allocating physical storage for the first data block;

storing the first data at the first data block; and

updating the first logical address to reference the first data block.

7. The method of claim 4 , wherein said second processing is included in data deduplication processing performed for a first write I/O operation that writes the first data to the first logical address of the first logical device.

8. The method of claim 3 , further comprising:

modifying or deleting content stored at the first logical address of the first logical device; and

responsive to said modifying or deleting content, performing second processing including:

decrementing the reference count of the first metadata of the first data block; and

updating the result of the first metadata from a first value to a second value, wherein said updating includes:

determining a first product by multiplying the first value by a modular multiplicative inverse of the first prime number that is assigned to the first logical device; and

determining the second value as the first value modulo the maximum prime number.

9. The method of claim 8 , wherein said modifying or deleting content stored at the first logical address of the first logical device is performed in connection with an I/O operation directed to the first logical address of the first logical device.

10. The method of claim 8 , wherein said modifying or deleting content stored at the first logical address of the first logical device is performed in connection with an operation that deletes the first logical device.

11. The method of claim 10 , wherein the operation that deletes the first logical device is a management operation received over a management or control path.

12. The method of claim 8 , wherein the modular multiplicative inverse of the first prime number that is assigned to the first logical device is included in a table of computed modular multiplicative inverses for a plurality of prime numbers each less than the maximum prime number.

13. The method of claim 3 , wherein C 1 is determined using a first value selected from a table of computed values, wherein the table includes a plurality of values corresponding to the first prime number, wherein each of the plurality of values is computed by raising the first prime number to a different integer power greater than 0, and wherein the first value is one of the plurality of values.

14. The method of claim 3 , wherein C 1 is a first precomputed value selected from a table.

15. A system comprising:

one or more processors; and

a memory comprising code stored thereon that, when executed by at least one of the one or more processors, performs a method of determining unique ownership of data blocks comprising:

selecting a first data block referenced by a first logical address of a first logical device, wherein first metadata for the first data block includes a reference count and a result and wherein the reference count denotes a number of references to the first data block and the result denotes a value used in determining sole unique ownership of the first data block;

determining C 1 , an expected value of the result of the first metadata when the first logical device is a sole unique owner of the first data block; and

performing first processing that determines whether the first logical device is the sole unique owner of the first data block, wherein the first processing includes:

determining whether C 1 equals a current value of the result of the first metadata; and

responsive to determining C 1 equals the current value of the result of the first metadata, determining that the first logical device is the sole unique owner of the first data block, and otherwise determining that the first logical device is not the sole unique owner of the first data block.

16. A non-transitory computer readable medium comprising code stored thereon that, when executed, performs a method of determining unique ownership of data blocks comprising:

selecting a first data block referenced by a first logical address of a first logical device, wherein first metadata for the first data block includes a reference count and a result and wherein the reference count denotes a number of references to the first data block and the result denotes a value used in determining sole unique ownership of the first data block;

determining C 1 , an expected value of the result of the first metadata when the first logical device is a sole unique owner of the first data block; and

performing first processing that determines whether the first logical device is the sole unique owner of the first data block, wherein the first processing includes:

determining whether C 1 equals a current value of the result of the first metadata; and

responsive to determining C 1 equals the current value of the result of the first metadata, determining that the first logical device is the sole unique owner of the first data block, and otherwise determining that the first logical device is not the sole unique owner of the first data block.

17. The non-transitory computer readable medium of claim 16 , wherein C 1 is determined using the reference count, a maximum prime number, a first prime number that is uniquely assigned to the first logical device.

18. The non-transitory computer readable medium of claim 17 , wherein the first logical device is one of a plurality of logical devices and each of the plurality of logical devices is assigned a different prime number less than the maximum prime number.

19. The non-transitory computer readable medium of claim 18 , wherein the method further comprises:

writing first data to the first logical address of the first logical device; and

responsive to said writing, performing second processing including:

associating the first data block with the first logical address, wherein the first logical address references the first data block;

incrementing the reference count of the first metadata of the first data block; and

updating the result of the first metadata from a first value to a second value, wherein said updating includes:

determining a first product by multiplying the first value by the first prime number that is assigned to the first logical device; and

determining the second value as the first value modulo the maximum prime number.

20. The non-transitory computer readable medium of claim 19 , wherein said second processing further comprises:

determining that the first data written to the first logical address is a duplicate of other data currently stored in the first data block; and

updating the first logical address to reference the first data block.