[stable24] Make config file saving safe against write failures #34093
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In case of disk space depletion, writing a new version of config fails, leaving the config file empty. This patch improves safety of updates to config.php by saving the new version of the config into a randomly-named temporary file in the same directory, and then renaming it to config.php, which renaming is atomic in POSIX-compliant filesystems and shouldn't involve disk space allocation. If writing the new config version is impossible, the current config remains unchanged. This patch drops the use of file locking as unnecessary. File locking merely established order in which the concurrent independent processes attempted file writing. In the end, the process which was last to update the file "wins" - their changes persist and the changes of previous writers are dropped as there's no conflict detection or change merging mechanism anyway. With the current change, there is still some resulting ordering, and the last writer still wins in the same way. Readers don't need file locking as well, as opening config.php for reading always provides a certain consistent version of the file. Signed-off-by: Andriy Utkin <dev@autkin.net>
nickvergessen
requested changes
Sep 19, 2022
Merged
|
closing, for the PR against master was reverted |
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backport of #34009