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-rw-r--r--internal/syscallcompat/quirks.go11
-rw-r--r--internal/syscallcompat/quirks_darwin.go2
-rw-r--r--internal/syscallcompat/quirks_linux.go44
-rw-r--r--internal/syscallcompat/sys_common.go74
-rw-r--r--internal/syscallcompat/sys_darwin.go4
-rw-r--r--internal/syscallcompat/sys_linux.go4
6 files changed, 90 insertions, 49 deletions
diff --git a/internal/syscallcompat/quirks.go b/internal/syscallcompat/quirks.go
index 858f16d..36bcb9f 100644
--- a/internal/syscallcompat/quirks.go
+++ b/internal/syscallcompat/quirks.go
@@ -5,18 +5,17 @@ import (
)
const (
- // QuirkBrokenFalloc means the falloc is broken.
+ // QuirkBtrfsBrokenFalloc means the falloc is broken.
// Preallocation on Btrfs is broken ( https://github.com/rfjakob/gocryptfs/issues/395 )
// and slow ( https://github.com/rfjakob/gocryptfs/issues/63 ).
- QuirkBrokenFalloc = uint64(1 << iota)
+ QuirkBtrfsBrokenFalloc = uint64(1 << iota)
// QuirkDuplicateIno1 means that we have duplicate inode numbers.
// On MacOS ExFAT, all empty files share inode number 1:
// https://github.com/rfjakob/gocryptfs/issues/585
QuirkDuplicateIno1
- // QuirkNoUserXattr means that user.* xattrs are not supported
- QuirkNoUserXattr
)
-func logQuirk(s string) {
- tlog.Info.Printf(tlog.ColorYellow + "DetectQuirks: " + s + tlog.ColorReset)
+// LogQuirk prints a yellow message about a detected quirk.
+func LogQuirk(s string) {
+ tlog.Info.Println(tlog.ColorYellow + "DetectQuirks: " + s + tlog.ColorReset)
}
diff --git a/internal/syscallcompat/quirks_darwin.go b/internal/syscallcompat/quirks_darwin.go
index 4adeea1..c4d5006 100644
--- a/internal/syscallcompat/quirks_darwin.go
+++ b/internal/syscallcompat/quirks_darwin.go
@@ -33,7 +33,7 @@ func DetectQuirks(cipherdir string) (q uint64) {
// On MacOS ExFAT, all empty files share inode number 1:
// https://github.com/rfjakob/gocryptfs/issues/585
if fstypename == FstypenameExfat {
- logQuirk("ExFAT detected, disabling hard links. See https://github.com/rfjakob/gocryptfs/issues/585 for why.")
+ LogQuirk("ExFAT detected, disabling hard links. See https://github.com/rfjakob/gocryptfs/issues/585 for why.")
q |= QuirkDuplicateIno1
}
diff --git a/internal/syscallcompat/quirks_linux.go b/internal/syscallcompat/quirks_linux.go
index 5ef2d8a..35f754d 100644
--- a/internal/syscallcompat/quirks_linux.go
+++ b/internal/syscallcompat/quirks_linux.go
@@ -1,11 +1,38 @@
package syscallcompat
import (
+ "syscall"
+
"golang.org/x/sys/unix"
"github.com/rfjakob/gocryptfs/v2/internal/tlog"
)
+// FS_NOCOW_FL is the flag set by "chattr +C" to disable copy-on-write on
+// btrfs. Not exported by golang.org/x/sys/unix, value from linux/fs.h.
+const FS_NOCOW_FL = 0x00800000
+
+// dirHasNoCow checks whether the directory at the given path has the
+// NOCOW (No Copy-on-Write) attribute set (i.e. "chattr +C").
+// When a directory has this attribute, files created within it inherit
+// NOCOW, which makes fallocate work correctly on btrfs because writes
+// go in-place rather than through COW.
+func dirHasNoCow(path string) bool {
+ fd, err := syscall.Open(path, syscall.O_RDONLY|syscall.O_DIRECTORY, 0)
+ if err != nil {
+ tlog.Debug.Printf("dirHasNoCow: Open %q failed: %v", path, err)
+ return false
+ }
+ defer syscall.Close(fd)
+
+ flags, err := unix.IoctlGetInt(fd, unix.FS_IOC_GETFLAGS)
+ if err != nil {
+ tlog.Debug.Printf("dirHasNoCow: FS_IOC_GETFLAGS on %q failed: %v", path, err)
+ return false
+ }
+ return flags&FS_NOCOW_FL != 0
+}
+
// DetectQuirks decides if there are known quirks on the backing filesystem
// that need to be workarounded.
//
@@ -21,14 +48,19 @@ func DetectQuirks(cipherdir string) (q uint64) {
// Preallocation on Btrfs is broken ( https://github.com/rfjakob/gocryptfs/issues/395 )
// and slow ( https://github.com/rfjakob/gocryptfs/issues/63 ).
//
+ // The root cause is that btrfs COW allocates new blocks on write even for
+ // preallocated extents, defeating the purpose of fallocate. However, if the
+ // backing directory has the NOCOW attribute (chattr +C), writes go in-place
+ // and fallocate works correctly.
+ //
// Cast to uint32 avoids compile error on arm: "constant 2435016766 overflows int32"
if uint32(st.Type) == unix.BTRFS_SUPER_MAGIC {
- logQuirk("Btrfs detected, forcing -noprealloc. See https://github.com/rfjakob/gocryptfs/issues/395 for why.")
- q |= QuirkBrokenFalloc
- }
-
- if uint32(st.Type) == unix.TMPFS_MAGIC {
- logQuirk("tmpfs detected, no extended attributes except acls will work.")
+ if dirHasNoCow(cipherdir) {
+ tlog.Debug.Printf("DetectQuirks: Btrfs detected but cipherdir has NOCOW attribute (chattr +C), fallocate should work correctly")
+ } else {
+ // LogQuirk is called in fusefrontend/root_node.go
+ q |= QuirkBtrfsBrokenFalloc
+ }
}
return q
diff --git a/internal/syscallcompat/sys_common.go b/internal/syscallcompat/sys_common.go
index 1aa6a6e..3cb9ffa 100644
--- a/internal/syscallcompat/sys_common.go
+++ b/internal/syscallcompat/sys_common.go
@@ -54,10 +54,10 @@ func Openat(dirfd int, path string, flags int, mode uint32) (fd int, err error)
flags |= syscall.O_EXCL
}
} else {
- // If O_CREAT is not used, we should use O_NOFOLLOW
- if flags&syscall.O_NOFOLLOW == 0 {
- tlog.Warn.Printf("Openat: O_NOFOLLOW missing: flags = %#x", flags)
- flags |= syscall.O_NOFOLLOW
+ // If O_CREAT is not used, we should use O_NOFOLLOW or O_SYMLINK
+ if flags&(unix.O_NOFOLLOW|OpenatFlagNofollowSymlink) == 0 {
+ tlog.Warn.Printf("Openat: O_NOFOLLOW/O_SYMLINK missing: flags = %#x", flags)
+ flags |= unix.O_NOFOLLOW
}
}
@@ -112,10 +112,10 @@ const XATTR_SIZE_MAX = 65536
// Make the buffer 1kB bigger so we can detect overflows. Unfortunately,
// slices larger than 64kB are always allocated on the heap.
-const XATTR_BUFSZ = XATTR_SIZE_MAX + 1024
+const GETXATTR_BUFSZ_BIG = XATTR_SIZE_MAX + 1024
// We try with a small buffer first - this one can be allocated on the stack.
-const XATTR_BUFSZ_SMALL = 500
+const GETXATTR_BUFSZ_SMALL = 500
// Fgetxattr is a wrapper around unix.Fgetxattr that handles the buffer sizing.
func Fgetxattr(fd int, attr string) (val []byte, err error) {
@@ -135,7 +135,7 @@ func Lgetxattr(path string, attr string) (val []byte, err error) {
func getxattrSmartBuf(fn func(buf []byte) (int, error)) ([]byte, error) {
// Fastpaths. Important for security.capabilities, which gets queried a lot.
- buf := make([]byte, XATTR_BUFSZ_SMALL)
+ buf := make([]byte, GETXATTR_BUFSZ_SMALL)
sz, err := fn(buf)
// Non-existing xattr
if err == unix.ENODATA {
@@ -159,7 +159,7 @@ func getxattrSmartBuf(fn func(buf []byte) (int, error)) ([]byte, error) {
// We choose the simple approach of buffer that is bigger than the limit on
// Linux, and return an error for everything that is bigger (which can
// only happen on MacOS).
- buf = make([]byte, XATTR_BUFSZ)
+ buf = make([]byte, GETXATTR_BUFSZ_BIG)
sz, err = fn(buf)
if err == syscall.ERANGE {
// Do NOT return ERANGE - the user might retry ad inifinitum!
@@ -182,42 +182,44 @@ out:
// Flistxattr is a wrapper for unix.Flistxattr that handles buffer sizing and
// parsing the returned blob to a string slice.
func Flistxattr(fd int) (attrs []string, err error) {
- // See the buffer sizing comments in getxattrSmartBuf.
- // TODO: smarter buffer sizing?
- buf := make([]byte, XATTR_BUFSZ)
- sz, err := unix.Flistxattr(fd, buf)
- if err == syscall.ERANGE {
- // Do NOT return ERANGE - the user might retry ad inifinitum!
- return nil, syscall.EOVERFLOW
+ listxattrSyscall := func(buf []byte) (int, error) {
+ return unix.Flistxattr(fd, buf)
}
- if err != nil {
- return nil, err
- }
- if sz >= XATTR_SIZE_MAX {
- return nil, syscall.EOVERFLOW
- }
- attrs = parseListxattrBlob(buf[:sz])
- return attrs, nil
+ return listxattrSmartBuf(listxattrSyscall)
}
// Llistxattr is a wrapper for unix.Llistxattr that handles buffer sizing and
// parsing the returned blob to a string slice.
func Llistxattr(path string) (attrs []string, err error) {
- // TODO: smarter buffer sizing?
- buf := make([]byte, XATTR_BUFSZ)
- sz, err := unix.Llistxattr(path, buf)
- if err == syscall.ERANGE {
- // Do NOT return ERANGE - the user might retry ad inifinitum!
- return nil, syscall.EOVERFLOW
+ listxattrSyscall := func(buf []byte) (int, error) {
+ return unix.Llistxattr(path, buf)
}
- if err != nil {
- return nil, err
- }
- if sz >= XATTR_SIZE_MAX {
- return nil, syscall.EOVERFLOW
+ return listxattrSmartBuf(listxattrSyscall)
+}
+
+// listxattrSmartBuf handles smart buffer sizing for Flistxattr and Llistxattr
+func listxattrSmartBuf(listxattrSyscall func([]byte) (int, error)) ([]string, error) {
+ const LISTXATTR_BUFSZ_SMALL = 100
+
+ // Blindly try with the small buffer first
+ buf := make([]byte, LISTXATTR_BUFSZ_SMALL)
+ sz, err := listxattrSyscall(buf)
+ if err == syscall.ERANGE {
+ // Did not fit. Find the actual size
+ sz, err = listxattrSyscall(nil)
+ if err != nil {
+ return nil, err
+ }
+ // ...and allocate the buffer to fit
+ buf = make([]byte, sz)
+ sz, err = listxattrSyscall(buf)
+ if err != nil {
+ // When an xattr got added between the size probe and here,
+ // we could fail with ERANGE. This is ok as the caller will retry.
+ return nil, err
+ }
}
- attrs = parseListxattrBlob(buf[:sz])
- return attrs, nil
+ return parseListxattrBlob(buf[:sz]), nil
}
func parseListxattrBlob(buf []byte) (attrs []string) {
diff --git a/internal/syscallcompat/sys_darwin.go b/internal/syscallcompat/sys_darwin.go
index 0ebdd3b..ef19f24 100644
--- a/internal/syscallcompat/sys_darwin.go
+++ b/internal/syscallcompat/sys_darwin.go
@@ -27,6 +27,10 @@ const (
// Only exists on Linux. Define here to fix build failure, even though
// we will never see this flag.
RENAME_WHITEOUT = 1 << 30
+
+ // On Darwin we use O_SYMLINK which allows opening a symlink itself.
+ // On Linux, we only have O_NOFOLLOW.
+ OpenatFlagNofollowSymlink = unix.O_SYMLINK
)
// Unfortunately fsetattrlist does not have a syscall wrapper yet.
diff --git a/internal/syscallcompat/sys_linux.go b/internal/syscallcompat/sys_linux.go
index 19d2c56..71478af 100644
--- a/internal/syscallcompat/sys_linux.go
+++ b/internal/syscallcompat/sys_linux.go
@@ -28,6 +28,10 @@ const (
RENAME_NOREPLACE = unix.RENAME_NOREPLACE
RENAME_WHITEOUT = unix.RENAME_WHITEOUT
RENAME_EXCHANGE = unix.RENAME_EXCHANGE
+
+ // On Darwin we use O_SYMLINK which allows opening a symlink itself.
+ // On Linux, we only have O_NOFOLLOW.
+ OpenatFlagNofollowSymlink = unix.O_NOFOLLOW
)
var preallocWarn sync.Once
generated by cgit v1.2.3 (git 2.39.1) at 2026-02-26 11:59:33 +0000