Filesystem having a filename cache

• US 7,987,190 B2
• Filed: 12/03/2010
• Issued: 07/26/2011
• Est. Priority Date: 08/25/2006
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: QNX Software Systems Company (Blackberry Limited)
• Inventors: ver der Veen, Peter, Dodge, Dan
• Primary Examiner(s): Abel-Jalil; Neveen
• Assistant Examiner(s): KINSAUL, DANIEL W
• Application Number:
  US12/960,197
• Publication Number:
  US 20110078219A1
• Time in Patent Office: 235 Days
• Field of Search: None
• US Class Current: 707/741
• CPC Class Codes: G06F 16/172 Caching, prefetching or hoarding of files

Abstract

A system comprising a processor, a data storage device that is accessible by the processor, and filesystem software that is executable by the processor to organize files on the data storage device are provided. The filesystem software is executable to maintain a filename cache having variable size filename entries. The filename entries may include a filename header section and a name section storing an entire filename of a corresponding file.

Claims

1. A system comprising:

a processor;

a data storage device accessible by the processor; and

a filesystem software executable by the processor to organize a plurality of files on the data storage device, where the filesystem software is executable to maintain a filename cache comprising a plurality of entries, where each entry of the plurality of entries comprises a filename header section and a name section, where the name section stores an entire filename of a corresponding file,

where the filesystem software is further executable to identify a given entire filename to be stored in the name section of one of the plurality of entries, determine a number of bytes to allocate to the name section of the one of the plurality of entries based on the given entire filename to be stored and to allocate the determined number of bytes to the given name section of the one of the plurality of entries, thereby creating a variable size filename entry,

where the filesystem software is further executable to characterize each of the plurality of entries based on a namesum value of each of the plurality of entries where the namesum value of each of the plurality of entries is calculated based on the entire filename stored in the name section of each of the plurality of entries,

where the filesystem software is further executable to generate an index into a hash table from the namesum value of at least one of the plurality of entries, and

where data in the hash table at the index directs the file system software to the at least one of the plurality of entries having a same namesum value.

2. The system of claim 1, where the filename header section of each of the plurality of entries comprises an index to a next entry of the plurality of entries characterized by a same namesum value.

3. The system of claim 2, where the filesystem software is further executable to receive a request for a file, calculate a namesum value of the requested file based on a filename of the requested file, identify a first entry of the plurality of entries characterized by the namesum value of the requested file, determine whether the first entry of the plurality of entries corresponds to the requested file, and access a second entry of the plurality of entries characterized by the namesum value of the requested file, based on the index stored in the name section of the first entry of the plurality of entries if the first entry of the plurality of entries does not correspond to the requested file.

4. The system of claim 1, where the filename header section comprises an information item uniquely identifying a file associated with the filename in the name section.

5. The system of claim 1, where the filename header section of at least one entry of the plurality of entries further comprises an information item indicative of whether the at least one entry corresponds to a first entry in the hash table for a particular namesum value.

6. The system of claim 1, where the filename header section of each entry of the plurality of entries comprises an information item indicative of whether the filename in the name section of each entry of the plurality of entries is not locatable on the system.

7. A method for operating a filesystem comprising:

allocating a storage space to a filename cache;

organizing the filename cache into a plurality of variable size filename entries, where each variable size filename entry of the plurality of variable size filename entries comprises a filename header section and a name section, where the name section stores a filename of a corresponding file;

identifying a given filename to be stored in the name section of one of the plurality of variable size filename entries;

determining a number of bytes to allocate to the name section of the one of the plurality of variable size filename entries based on the given filename to be stored;

allocating the determined number of bytes to the given name section of the one of the plurality of variable size filename entries; and

characterizing each of the plurality of variable size filename entries based on a namesum value of each of the plurality of variable size filename entries,

where the namesum value of each of the plurality of variable size filename entries is calculated based on the filename stored in the name section of each of the plurality of variable size filename entries,

where an index into a hash table is generated from the namesum value of at least one of the plurality of variable size filename entries, and

where data in the hash table at the index includes a pointer to the at least one of the plurality of variable size filename entries having a same namesum value.

8. The method of claim 7, where the storage space allocated for the filename cache comprises a ring-type buffer.

9. The method of claim 8, further comprising adding a plurality of dummy filename entries to compensate for wrap-around writing of the plurality of variable size filename entries to the ring-type buffer.

10. The method of claim 7, further comprising calculating a namesum using a requested filename of a requested file.

11. The method of claim 10, further comprising generating an index from the calculated namesum.

12. The method of claim 11, further comprising:

using the index from the calculated namesum to obtain an initial pointer from the hash table; and

using the initial pointer to access a first variable size filename entry of the plurality of variable size filename entries in the filename cache having the calculated namesum.

13. The method of claim 12, further comprising comparing the requested filename to the filename stored in the name section of the first variable size filename entry for a match.

14. The method of claim 13, where the filename header section of the first variable size filename entry comprises an information item corresponding to a parent directory of the corresponding file.

15. The method of claim 14, further comprising comparing a parent directory information item of the requested file to the information item of the filename header section of the first variable size filename entry to determine whether there is a match between the requested file and the file corresponding to the first variable size filename entry.

16. A storage medium comprising code adapted to execute a method for operating a filesystem comprising:

allocating a storage space to a filename cache;

organizing the filename cache into a plurality of variable size filename entries, where each variable size filename entry of the plurality of variable size filename entries comprises a filename header section and a name section, where the name section stores a filename of a corresponding file; and

characterizing each of the plurality of variable size filename entries based on a namesum value of each of the plurality of variable size filename entries,

where the namesum value of each of the plurality of variable size filename entries is calculated based on the filename stored in the name section of each of the plurality of variable size filename entries,

where an index into a hash table is generated from the namesum value of at least one of the plurality of variable size filename entries, and

where data in the hash table at the index includes a pointer to the at least one of the plurality of variable size filename entries having a same namesum value.

17. The storage medium of claim 16, where the storage space allocated for the filename cache by the method comprises a ring-type buffer.

18. The storage medium of claim 17, where the method further comprises adding a plurality of dummy filename entries to compensate for wrap-around writing of the plurality of variable size filename entries to the ring-type buffer.

19. The storage medium of claim 16, where the method further comprises calculating a namesum using a requested filename of a requested file.

20. The storage medium of claim 19, where the method further comprises:

using the namesum calculated from the requested file as an index into the hash table to obtain the pointer from the hash table; and

using the pointer to access a first variable size filename entry in the filename cache having the calculated namesum.