Semiconductor storage device and method for controlling nonvolatile semiconductor memory
View Patent ↗According to embodiments, a controller comprises a write control unit that performs writing in a nonvolatile semiconductor memory, and an area management unit that causes the write control unit to perform write processing until a spare area not storing valid data is not present in the nonvolatile semiconductor memory, and transmits an error to a host when the spare area is not present.
1. A semiconductor storage device comprising:
a nonvolatile semiconductor memory having a plurality of blocks; and
a controller configured to
calculate a first value indicating amount of data corresponding to addresses which are unwritten in the nonvolatile semiconductor memory among logical addresses contained in a received write instruction from a host,
calculate a second value, the second value being derived by adding a third value to the first value, the third value being current amount of valid data,
calculate a fourth value indicating a current storage capacity usable as a storage area in the nonvolatile semiconductor memory, and
in a case where the second value does not exceed the fourth value, perform a write processing based on the received write instruction.
2. The semiconductor storage device according to claim 1 , wherein, in a case where the second value exceeds the fourth value, the controller notifies an error to the host.
3. The semiconductor storage device according to claim 1 , wherein the fourth value is derived by adding a spare storage area capacity to a storage area capacity corresponding to a logical address designated by the host and subtracting a bad area capacity unusable as a storage area therefrom.
4. The semiconductor storage device according to claim 2 , wherein, when the second value lowers the fourth value by executing a deletion instruction, the controller enables the write processing again.
5. The semiconductor storage device according to claim 1 , wherein the third value and the fourth value are notified to the host in response to a request from the host.
6. A method for controlling a nonvolatile semiconductor memory having a plurality of blocks, the method comprising:
calculating a first value indicating amount of data corresponding to addresses which are unwritten in the nonvolatile semiconductor memory among logical addresses contained in a received write instruction from a host,
calculating a second value, the second value being derived by adding a third value to the first value, the third value being current amount of valid data,
calculating a fourth value indicating a current storage capacity usable as a storage area in the nonvolatile semiconductor memory,
in a case where the second value does not exceed the fourth value, performing a write processing based on the received write instruction.
7. The method according to claim 6 , further comprising
in a case where the second value exceeds the fourth value, notifying an error to the host.
8. The method according to claim 6 , wherein the fourth value is derived by adding a spare storage area capacity to a storage area capacity corresponding to a logical address designated by the host and subtracting a bad area capacity unusable as a storage area therefrom.
9. The method according to claim 7 , further comprising
when the second value lowers the fourth value by executing a deletion instruction, enabling the write processing again.
10. The method according to claim 6 , further comprising
notifying the host of the third value and the fourth value in response to a request from the host.