fix(ecstore): keep O_DIRECT for eligible reads via native io_uring (backlog#1102) (#4649)

fix(ecstore): keep O_DIRECT for eligible reads via native io_uring (rustfs/backlog#1102)

Wire ecstore's io_uring read backend to rustfs-uring's native aligned
O_DIRECT read (`read_at_direct`, merged in rustfs/uring#3), so an
O_DIRECT-eligible read keeps BOTH io_uring's async submission AND
O_DIRECT's page-cache bypass instead of trading one for the other.

`UringBackend::pread_bytes` now selects the read shape by a tiered,
per-disk-latched ladder — never a blanket downgrade:

  1. io_uring latched off for this disk (backlog#1101) -> StdBackend.
  2. O_DIRECT-eligible + native path usable -> pread_uring_direct: open
     the file O_DIRECT, probe the device alignment once (cached), and
     read via read_at_direct. Best path: async + no cache pollution.
  3. O_DIRECT-eligible but the fs refused O_DIRECT earlier (latched)
     -> StdBackend aligned path (which itself degrades to buffered).
  4. non-O_DIRECT read -> buffered pread_uring.

Latching keeps a failure from being re-attempted per-read: an fs that
refuses O_DIRECT (EINVAL/EOPNOTSUPP on open) latches the native direct
path off for that disk; a restriction-class errno from the read latches
io_uring off wholesale (backlog#1101). Any other error falls back for
that one read without masking a genuine data problem as a permanent
downgrade. The alignment comes from the existing probe_direct_io_align
(statx STATX_DIOALIGN, default 4096) and is cached in a per-disk
OnceLock so the probe runs at most once.

This replaces the interim guard that routed every O_DIRECT-eligible read
to StdBackend (which disabled io_uring on the hottest shard reads); the
native path is now the default and StdBackend is only a fallback tier.
Bumps the rustfs-uring pin to the merged #3 commit.

Verified on a real Linux host (16-core, real io_uring + O_DIRECT):
cargo check --tests, clippy -D warnings, and disk::local tests all pass
(128 passed, 0 failed), including uring_preserves_o_direct_for_eligible_reads
across unaligned ranges.

Co-authored-by: heihutu <heihutu@gmail.com>

crates/ecstore/Cargo.toml

@@ -145,7 +145,7 @@ metrics = { workspace = true }
 # scripts/check_no_tokio_io_uring.sh allows an explicit io-uring integration;
 # only the tokio "io-uring" runtime feature is banned.
 [target.'cfg(target_os = "linux")'.dependencies]
-rustfs-uring = { git = "https://github.com/rustfs/uring", rev = "39018c09cde98b380658f1a1511349a3574daddf" }
+rustfs-uring = { git = "https://github.com/rustfs/uring", rev = "f577ba0bfd6c3d74f9bdc54b573b8fcb45d6bc22" }
 
 [dev-dependencies]
 tokio = { workspace = true, features = ["rt-multi-thread", "macros", "test-util"] }