diff options
Diffstat (limited to 'db.go')
| -rw-r--r-- | db.go | 54 |
1 files changed, 40 insertions, 14 deletions
@@ -205,9 +205,17 @@ func Open(path string, mode os.FileMode, options *Options) (*DB, error) { if _, err := db.file.ReadAt(buf[:], 0); err == nil { m := db.pageInBuffer(buf[:], 0).meta() if err := m.validate(); err != nil { - return nil, err + // If we can't read the page size, we can assume it's the same + // as the OS -- since that's how the page size was chosen in the + // first place. + // + // If the first page is invalid and this OS uses a different + // page size than what the database was created with then we + // are out of luck and cannot access the database. + db.pageSize = os.Getpagesize() + } else { + db.pageSize = int(m.pageSize) } - db.pageSize = int(m.pageSize) } } @@ -274,12 +282,13 @@ func (db *DB) mmap(minsz int) error { db.meta0 = db.page(0).meta() db.meta1 = db.page(1).meta() - // Validate the meta pages. - if err := db.meta0.validate(); err != nil { - return err - } - if err := db.meta1.validate(); err != nil { - return err + // Validate the meta pages. We only return an error if both meta pages fail + // validation, since meta0 failing validation means that it wasn't saved + // properly -- but we can recover using meta1. And vice-versa. + err0 := db.meta0.validate() + err1 := db.meta1.validate() + if err0 != nil && err1 != nil { + return err0 } return nil @@ -351,6 +360,7 @@ func (db *DB) init() error { m.root = bucket{root: 3} m.pgid = 4 m.txid = txid(i) + m.checksum = m.sum64() } // Write an empty freelist at page 3. @@ -790,10 +800,26 @@ func (db *DB) pageInBuffer(b []byte, id pgid) *page { // meta retrieves the current meta page reference. func (db *DB) meta() *meta { - if db.meta0.txid > db.meta1.txid { - return db.meta0 + // We have to return the meta with the highest txid which doesn't fail + // validation. Otherwise, we can cause errors when in fact the database is + // in a consistent state. metaA is the one with the higher txid. + metaA := db.meta0 + metaB := db.meta1 + if db.meta1.txid > db.meta0.txid { + metaA = db.meta1 + metaB = db.meta0 + } + + // Use higher meta page if valid. Otherwise fallback to previous, if valid. + if err := metaA.validate(); err == nil { + return metaA + } else if err := metaB.validate(); err == nil { + return metaB } - return db.meta1 + + // This should never be reached, because both meta1 and meta0 were validated + // on mmap() and we do fsync() on every write. + panic("bolt.DB.meta(): invalid meta pages") } // allocate returns a contiguous block of memory starting at a given page. @@ -954,12 +980,12 @@ type meta struct { // validate checks the marker bytes and version of the meta page to ensure it matches this binary. func (m *meta) validate() error { - if m.checksum != 0 && m.checksum != m.sum64() { - return ErrChecksum - } else if m.magic != magic { + if m.magic != magic { return ErrInvalid } else if m.version != version { return ErrVersionMismatch + } else if m.checksum != 0 && m.checksum != m.sum64() { + return ErrChecksum } return nil } |