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authorBen Johnson <benbjohnson@yahoo.com>2016-04-24 14:11:19 -0600
committerBen Johnson <benbjohnson@yahoo.com>2016-04-24 14:11:19 -0600
commitd97499360d1ecebc492ea66c7447ea948f417620 (patch)
treed4775957ac2ec92ba8d37b39c386ea340a4e6473 /db.go
parentMerge branch 'LK4D4-pool_allocate' (diff)
parentadd additional meta page tests (diff)
downloaddedo-d97499360d1ecebc492ea66c7447ea948f417620.tar.gz
dedo-d97499360d1ecebc492ea66c7447ea948f417620.tar.xz
Merge branch 'cyphar-548-fix-errors-with-unsynced-metadata'
Diffstat (limited to 'db.go')
-rw-r--r--db.go54
1 files changed, 40 insertions, 14 deletions
diff --git a/db.go b/db.go
index 9048f6c..1223493 100644
--- a/db.go
+++ b/db.go
@@ -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
}