Memory system, controller, and method for controlling memory system

1. A memory system comprising:

a nonvolatile memory;

a storage unit storing a translation table indicating, by a first management unit, relationships between logical addresses specified by a host and physical addresses in the nonvolatile memory; and

a controller, when receiving, from the host, a delete notification indicating a delete area specified by a logical address, the delete area being smaller than the first management unit, configured to:

read first data from a first area in the first management unit of the nonvolatile memory, the first data including second data and third data, the second data having a physical address corresponding to the delete area, the third data having a physical address not corresponding to the delete area;

merge a specified data pattern and the third data; and

write the merged data to a second area in the first management unit of the nonvolatile memory.

2. The memory system according to claim 1 , wherein, when receiving the delete notification, the controller writes an invalid value to a physical address corresponding in the translation table to the first area and releases the first area.

3. The memory system according to claim 1 , further comprising:

a detection unit detecting the specified data pattern in data read from the nonvolatile memory, wherein

the controller is configured to, based on a detection result by the detection unit, in a case where a releasable first management unit exists in the data read from the nonvolatile memory, all of an area in the releasable first management unit including the specified data pattern, write an invalid value to a physical address corresponding in the translation table to the area of the releasable first management unit and release an area of a logical address of the releasable first management unit.

4. The memory system according to claim 2 , further comprising:

a detection unit detecting the specified data pattern in data read from the nonvolatile memory, wherein

the controller is configured to, based on a detection result by the detection unit, in a case where a releasable first management unit exists in the data read from the nonvolatile memory, all of an area in the releasable first management unit including the specified data pattern, write an invalid value to a physical address corresponding in the translation table to the area of the releasable first management unit and release an area of a logical address of the releasable first management unit.

5. The memory system according to claim 1 , wherein the controller

writes the specified data pattern to the nonvolatile memory when receiving a write request of the specified data pattern from the host, and

returns to the host the specified data pattern as read data in a case where the host makes a read request to a logical address that an invalid value is written to a corresponding physical address in the translation table.

6. The memory system according to claim 3 , wherein the detection unit detects the specified data pattern upon defragmenting a plurality of second management units larger than a sector into the first management unit, the first management unit being larger than the second management unit.

7. The memory system according to claim 1 , wherein the first management unit is larger than a sector.

8. A memory controller configured to control a nonvolatile memory, the memory controller comprising:

a storage unit storing a translation table indicating, by a first management unit, relationships between logical addresses specified by a host and physical addresses in the nonvolatile memory; and

a controller, when receiving, from the host, a delete notification indicating a delete area specified by a logical address, the delete area being smaller than the first management unit, configured to

read first data from a first area in the first management unit of the nonvolatile memory, the first data including second data and third data, the second data having a physical address corresponding to the delete area, the third data having a physical address not corresponding to the delete area,

merge a specified data pattern and the third data, and

write the merged data to a second area in the first management unit of the nonvolatile memory.

9. The memory controller according to claim 8 , wherein, when receiving the delete notification, the controller writes an invalid value to a physical address corresponding in the translation table to the first area and releases the first area.

10. The memory controller according to claim 8 , wherein the controller is configured to

detect the specified data pattern in data read from the nonvolatile memory, and

in a case where a releasable first management unit exists in the data read from the nonvolatile memory, all of an area in the releasable first management unit including the specified data pattern, write an invalid value to a physical address corresponding in the translation table to the area of the releasable first management unit and release an area of a logical address of the releasable first management unit.

11. The memory controller according to claim 9 , wherein the controller is configured to

detect the specified data pattern in data read from the nonvolatile memory, and

in a case where a releasable first management unit exists in the data read from the nonvolatile memory, all of an area in the releasable first management unit including the specified data pattern, write an invalid value to a physical address corresponding in the translation table to the area of the releasable first management unit and release an area of a logical address of the releasable first management unit.

12. The memory controller according to claim 8 , wherein the controller is configured to

write the specified data pattern to the nonvolatile memory when receiving a write request of the specified data pattern from the host, and

return to the host the specified data pattern as read data when the host makes a read request to a logical address that an invalid value is written to a corresponding physical address in the translation table.

13. The memory controller according to claim 10 , wherein the controller is configured to detect any one of presence and absence of the specified data pattern upon defragmenting a plurality of second management units larger than a sector into the first management unit, the first management unit being larger than the second management unit.

14. A method for controlling a nonvolatile memory, the method comprising:

managing a translation table indicating, by a first management unit, relationships between logical addresses specified by a host and physical addresses in the nonvolatile memory;

when receiving, from the host, a delete notification indicating a delete area smaller specified by a logical address, the delete area being smaller than the first management unit;

reading first data from a first area in the first management unit of the nonvolatile memory, the first data including second data and third data, the second data having a physical address corresponding to the delete area, the third data having a physical address not corresponding to the delete area;

merging a specified data pattern and the third data; and

writing the merged data to a second area in the first management unit of the nonvolatile memory.

15. The method according to claim 14 , further comprising:

when receiving the delete notification, writing an invalid value to a physical address corresponding in the translation table to the first area and releasing the first area.

16. The method according to claim 14 , further comprising:

detecting the specified data pattern in data read from the nonvolatile memory;

in a case where a releasable first management unit exists in the data read from the nonvolatile memory, all of an area in the releasable first management unit including the specified data pattern, writing an invalid value to a physical address corresponding in the translation table to the area of the releasable first management unit and releasing an area of a logical address of the releasable first management unit.

17. The method according to claim 15 , further comprising:

detecting the specified data pattern in data read from the nonvolatile memory;

in a case where a releasable first management unit exists in the data read from the nonvolatile memory, all of an area in the releasable first management unit including the specified data pattern, writing an invalid value to a physical address corresponding in the translation table to the area of the releasable first management unit and releasing an area of a logical address of the releasable first management unit.

18. The method according to claim 14 , further comprising:

writing the specified data pattern to the nonvolatile memory when receiving a write request of the specified data pattern from the host; and

returning to the host the specified data pattern as read data when the host makes a read request to a logical address that an invalid value is written to a corresponding physical address in the translation table.

19. The method according to claim 17 , further comprising:

detecting any one of presence and absence of the specified data pattern upon defragmenting a plurality of second management units larger than a sector into the first management unit, the first management unit being larger than the second management unit.

20. The method according to claim 14 , wherein the first management unit is larger than a sector.