posix_fallocate extremely slow on ext3 file system

posix_fallocate is extremely slow on ext3 file system (~12s for 8mb file) when file is opened with O_DSYNC flag.
This causes overall slowdown in dqlite execution when log/snapshot files are to be written. For instance, the average response time per request increases from 5ms for 1000 requests to a sluggish 25ms for 10,000 requests on our 3 node cluster setup.

I tried manualling setting fallocate to false in uv_fs.c [here](https://github.com/LakshK98/dqlite/blob/2eadfe4dd6f06272aa95283892544e6347870c31/src/raft/uv_fs.c#L202) so that the fallocate emulation logic is executed. This reduces avg response time for 10k requests to around 5-6 ms.

Would it possible to set fallocate to false on ext3 file systems in probeFallocate?

The report points to src/raft/uv_fs.c, including probeFallocate and the fallocate handling around line 202. Read that path first, then verify behavior on ext3 with O_DSYNC; done means ext3 selects the emulation path without regressing other filesystems.

Written by the indexing model from the issue text.