Mercurial > hg
view mercurial/mpatch.h @ 50316:87f0155d68aa stable
revlog: improve the robustness of the splitting process
The previous "in-place" splitting, preserving the splitting on transaction
failure had a couple of issue in case of transaction rollback:
- a race windows that could still lead to a crash and data loss
- it corrupted the `fncache`.
So instead, we use a new approach that we summarized as "we do a backup of the
inline revlog pre-split, and we restore this in case of failure".
To make readers live easier, we don't overwrite the inline index file until
transaction finalization. (once the transaction get into its finalization phase,
it is not expected to rollback, unless some crash happens).
To do so, we write the index of the split index in a temporary file that we use
until transaction finalization. We also keep a backup of the initial inline file
to be able to rollback the split if needed.
As a result, transaction rollback cancel the split and no longer corrupt
fncache. We also no longer have a small inconsistency windows where the
transaction could be unrecoverable.
author | Pierre-Yves David <pierre-yves.david@octobus.net> |
---|---|
date | Mon, 20 Mar 2023 11:52:17 +0100 |
parents | d86908050375 |
children |
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#ifndef HG_MPATCH_H #define HG_MPATCH_H #define MPATCH_ERR_NO_MEM -3 #define MPATCH_ERR_CANNOT_BE_DECODED -2 #define MPATCH_ERR_INVALID_PATCH -1 struct mpatch_frag { int start, end, len; const char *data; }; struct mpatch_flist { struct mpatch_frag *base, *head, *tail; }; int mpatch_decode(const char *bin, ssize_t len, struct mpatch_flist **res); ssize_t mpatch_calcsize(ssize_t len, struct mpatch_flist *l); void mpatch_lfree(struct mpatch_flist *a); int mpatch_apply(char *buf, const char *orig, ssize_t len, struct mpatch_flist *l); struct mpatch_flist * mpatch_fold(void *bins, struct mpatch_flist *(*get_next_item)(void *, ssize_t), ssize_t start, ssize_t end); #endif