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fs: Add safe locking semantics for format.json (#4523)

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This patch also reverts previous changes which were
merged for migration to the newer disk format. We will
be bringing these changes in subsequent releases. But
we wish to add protection in this release such that
future release migrations are protected.

Revert "fs: Migration should handle bucketConfigs as regular objects. (#4482)"
This reverts commit 976870a391.

Revert "fs: Migrate object metadata to objects directory. (#4195)"
This reverts commit 76f4f20609.
This commit is contained in:
Harshavardhana
2017-06-12 17:40:28 -07:00
committed by GitHub
parent b8463a738c
commit 075b8903d7
20 changed files with 509 additions and 933 deletions
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35
pkg/lock/lock_nix.go
View File

@@ -24,16 +24,12 @@ import (
"syscall"
)
// LockedOpenFile - initializes a new lock and protects
// the file from concurrent access across mount points.
// This implementation doesn't support all the open
// flags and shouldn't be considered as replacement
// for os.OpenFile().
func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
var lockType int
// Internal function implements support for both
// blocking and non blocking lock type.
func lockedOpenFile(path string, flag int, perm os.FileMode, lockType int) (*LockedFile, error) {
switch flag {
case syscall.O_RDONLY:
lockType = syscall.LOCK_SH
lockType |= syscall.LOCK_SH
case syscall.O_WRONLY:
fallthrough
case syscall.O_RDWR:
@@ -41,7 +37,7 @@ func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error
case syscall.O_WRONLY | syscall.O_CREAT:
fallthrough
case syscall.O_RDWR | syscall.O_CREAT:
lockType = syscall.LOCK_EX
lockType |= syscall.LOCK_EX
default:
return nil, fmt.Errorf("Unsupported flag (%d)", flag)
}
@@ -53,6 +49,9 @@ func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error
if err = syscall.Flock(int(f.Fd()), lockType); err != nil {
f.Close()
if err == syscall.EWOULDBLOCK {
err = ErrAlreadyLocked
}
return nil, err
}
@@ -73,3 +72,21 @@ func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error
return &LockedFile{File: f}, nil
}
// TryLockedOpenFile - tries a new write lock, functionality
// it is similar to LockedOpenFile with with syscall.LOCK_EX
// mode but along with syscall.LOCK_NB such that the function
// doesn't wait forever but instead returns if it cannot
// acquire a write lock.
func TryLockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
return lockedOpenFile(path, flag, perm, syscall.LOCK_NB)
}
// LockedOpenFile - initializes a new lock and protects
// the file from concurrent access across mount points.
// This implementation doesn't support all the open
// flags and shouldn't be considered as replacement
// for os.OpenFile().
func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
return lockedOpenFile(path, flag, perm, 0)
}