Bug 192562

Summary: [GLib] FileSystem::moveFile() should fall back to copying
Product: WebKit Reporter: Adrian Perez <aperez>
Component: WebCore Misc.Assignee: Adrian Perez <aperez>
Severity: Normal CC: cgarcia, commit-queue, darin, mcatanzaro, mmaxfield, webkit-bug-importer, ysuzuki, zan
Priority: P2 Keywords: InRadar
Version: Other   
Hardware: Unspecified   
OS: Unspecified   
Bug Depends on:    
Bug Blocks: 154553    
Description Flags
Patch none

Description Adrian Perez 2018-12-10 11:32:58 PST
Note that:

 - Cocoa (in “Source/WebCore/platform/cocoa/FileSystemCocoa.mm”) uses
   [NSFileManager movItemAtURL:toURL:], which falls back to copying, as per

 - Windows (in “Source/WebCore/platform/win/FileSystemWin.cpp”) uses

But in the other hand:

 - “Source/WebCore/platform/posix/FileSystemPOSIX.cpp” uses a plain
   rename(2), which does NOT fall-back to copying.

 - “Source/WebCore/platform/glib/FileSystemGlib.cpp” uses g_rename(),
   which ends up calling rename(2) -- why this does not simply use
   the POSIX implmentation beats me ¯\_(ツ)_/¯

While working on the content extensions code, I have noticed that compiling
a content extension involves creating a temporary file, and then moving it
to its final location. For the GLib-based ports (GTK+, WPE) on Unix, the
temporary file will be created under “/tmp”, and then FileSystem::moveFile()
is used to place it in its final location, typically under the user's $HOME

There is a catch, though: frequently “/tmp” is on a different mount point
than the final location! This is *very* often true in modern GNU/Linux
distributions that have “/tmp” on tmpfs. Or, even if “/tmp” is the same
file system as “/”, not uncommonly “/home” can be a separate file system

To me it is quite clear that FileSyste::moveFile() has to fall-back to
copying, otherwise anything that makes use if this function will be far
too easy to randomly break in unexptected ways.
Comment 1 Adrian Perez 2018-12-10 11:42:11 PST
For FileSystemGLib I am planning to rewrite the function to use
g_file_move(), which does implements a copy+delete fallback.
Comment 2 Adrian Perez 2018-12-10 11:56:08 PST
Created attachment 356977 [details]
Comment 3 WebKit Commit Bot 2018-12-10 12:46:36 PST
Comment on attachment 356977 [details]

Clearing flags on attachment: 356977

Committed r239043: <https://trac.webkit.org/changeset/239043>
Comment 4 WebKit Commit Bot 2018-12-10 12:46:38 PST
All reviewed patches have been landed.  Closing bug.
Comment 5 Radar WebKit Bug Importer 2018-12-10 12:47:27 PST