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Switched back to simple deorphan-step on directory remove

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Originally I tried to reuse the indirect delete to accomplish truely
atomic directory removes, however this fell apart when it came to
implementing directory removes as a side-effect of renames.

A single indirect-delete simply can't handle renames with removes as
a side effects. When copying an entry to its destination, we need to
atomically delete both the old entry, and the source of our copy. We
can't delete both with only a single indirect-delete. It is possible to
accomplish this with two indirect-deletes, but this is such an uncommon
case that it's really not worth supporting efficiently due to how
expensive globals are.

I also dropped indirect-deletes for normal directory removes. I may add
it back later, but at the moment it's extra code cost for that's not
traveled very often.

As a result, restructured the indirect delete handling to be a bit more
generic, now with a multipurpose lfs_globals_t struct instead of the
delete specific lfs_entry_t struct.

Also worked on integrating xored-globals, now with several primitive
global operations to manage fetching/updating globals on disk.
This commit is contained in:
Christopher Haster
2018-07-01 22:29:42 -05:00
parent 3ffcedb95b
commit cebf7aa0fe
3 changed files with 323 additions and 96 deletions
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lfs.h
+15 -8
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@@ -129,7 +129,7 @@ enum lfs_type {
// internal sources
LFS_FROM_REGION = 0x000,
LFS_FROM_DISK = 0x200,
LFS_FROM_MOVE = 0x004,
LFS_FROM_MOVE = 0x0ff,
};
// File open flags
@@ -296,10 +296,17 @@ typedef struct lfs_mattrlist {
struct lfs_mattrlist *next;
} lfs_mattrlist_t;
typedef struct lfs_entry {
lfs_block_t pair[2];
uint16_t id;
} lfs_entry_t;
//typedef struct lfs_entry {
// lfs_block_t pair[2];
// uint16_t id;
//} lfs_entry_t;
typedef struct lfs_globals {
struct lfs_move {
lfs_block_t pair[2];
uint16_t id;
} move;
} lfs_globals_t;
typedef struct lfs_mdir {
lfs_block_t pair[2];
@@ -310,7 +317,7 @@ typedef struct lfs_mdir {
uint16_t count;
bool erased;
bool split;
lfs_entry_t idelete;
lfs_globals_t globals;
bool stop_at_commit; // TODO hmmm
uint16_t moveid; // TODO rm me
} lfs_mdir_t;
@@ -380,8 +387,8 @@ typedef struct lfs {
lfs_free_t free;
bool deorphaned;
lfs_entry_t idelete;
lfs_entry_t diff;
lfs_globals_t globals;
lfs_globals_t diff;
lfs_size_t inline_size;
lfs_size_t attrs_size;