|SYNC(2)||Linux Programmer's Manual||SYNC(2)|
int syncfs(int fd);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
syncfs() is like sync(), but synchronizes just the filesystem containing file referred to by the open file descriptor fd.
syncfs() can fail for at least the following reasons:
- fd is not a valid file descriptor.
- An error occurred during synchronization. This error may relate to data written to any file on the filesystem, or on metadata related to the filesystem itself.
- Disk space was exhausted while synchronizing.
- ENOSPC, EDQUOT
- Data was written to a files on NFS or another filesystem which does not allocate space at the time of a write(2) system call, and some previous write failed due to insufficient storage space.
syncfs() is Linux-specific.
According to the standard specification (e.g., POSIX.1-2001), sync() schedules the writes, but may return before the actual writing is done. However Linux waits for I/O completions, and thus sync() or syncfs() provide the same guarantees as fsync() called on every file in the system or filesystem respectively.
In mainline kernel versions prior to 5.8, syncfs() will fail only when passed a bad file descriptor (EBADF). Since Linux 5.8, syncfs() will also report an error if one or more inodes failed to be written back since the last syncfs() call.