Method and apparatus to perform incremental truncates in a file system
View Patent ↗The present invention provides a computer implemented method for truncating a file in a file system. The file system receives a request to truncate a file to a target size, the file having a first inode. The file system creates a second inode to a transient directory, wherein the second inode holds a plurality of in-progress entries. The file system sets a target size in the first inode. The file system writes a truncate entry to a journal, the truncate entry comprising a predetermined size. The file system truncates the file by up to the predetermined size. The file system determines that the file is above the target size. Responsive to a determination that the file is above the target size, the file system repeats the truncating step and the determining step. Responsive to a determination that the file is not above the target size, the file system applies the in-progress entries from the transient directory.
1. A computer implemented method for truncating a file in a file system, the method comprising:
receiving a request to truncate the file to a target size, the file having a primary inode;
creating a transient directory inode, wherein the transient directory inode holds a plurality of in-progress entries;
setting a target size in the primary inode;
writing a truncate entry to a journal, the truncate entry comprising a predetermined size;
truncating the file by up to the predetermined size;
determining that the file is above the target size;
responsive to a determination that the file is above the target size, repeating the truncating step and the determining step;
responsive to a determination that the file is not above the target size, apply the in-progress entries from the transient directory inode;
determining whether a used buffer count is equal to a maximum buffer count;
responsive to a determination that the used buffer count is not equal to the maximum buffer count, obtaining a lock to at least one entity;
responsive to a determination that the used buffer count is equal to the maximum buffer count, increasing the used buffer count;
responsive to a determination that the used buffer count is equal to the maximum buffer count, performing the receiving, creating, setting, writing, determining, repeating, and removing steps;
releasing the lock; and
decreasing the used buffer count of a buffer cache, whereby the buffer cache is not exhausted.
2. The computer implemented method of claim 1 further comprising:
setting an operation flag in the primary inode to track buffers in use.
3. The computer implemented method of claim 2 further comprising:
removing the file.
4. The computer implemented method of claim 1 further comprising:
determining that a used buffer count is equal to a maximum buffer count;
responsive to a determination that the used buffer count is equal to a maximum buffer count, queuing a thread; and
awakening the thread.
5. The computer implemented method of claim 4 , wherein the step of increasing the used buffer count comprises increasing the used buffer count by one.