On 5 November 2010 09:37, Colomban Wendling lists.ban@herbesfolles.org wrote:
Le 04/11/2010 21:42, Dimitar Zhekov a écrit :
On Thu, 4 Nov 2010 17:53:47 +0000 Nick Treleaven nick.treleaven@btinternet.com wrote:
So it seems that function doesn't handle disk exhaustion safely. (But this is no worse than before for Geany).
Before we had safe or unsafe file saving. Let's keep that choice, shall we? I can write the patch, it's only a few lines.
For more than 20 years now, the only safe save is to write the data into a temporary file in the same directory, and then rename it over the target file. Even if the rename fails, you still have the temporary file. That changes the onwership and permissions, which is exactly the behaviour of the safe g_file_set_contents().
Well... stop me if I'm saying bullshit but what about:
backup = path + '~' # or whatever if copy (path, backup_path): # COPY file to the backup if not write (path, data): # write in original file move (backup_path, path) # if write failed, restore backup elif not make_backup: unlink (backup_path) # if no backup is to be done, delete backup
The problems I see are: 1) needs at least 2 times the size of the file in the target directory (but it's the same anytime we bake backups) 2) backup file may have altered permissions/attrs 3) ...so if write fails, we have changed the permissions/attrs on the original file In the worst case, the original file has another name and lost its permissions/attrs.
The advantages I see are: 1) the permissions/attrs are kept on success, as well as hard links 2) no data can be lost (if the FS is reliable)
The key idea is not to move the original file but to copy it. So we can safely overwrite the original (and the keep permissions/attrs), once the backup is done.
Thoughts?
Hi,
It seems to me that g_file_set_contents behavior can be described as "write new file with the name of an existing file" so new file permissions and hard links point to the old file.
Columbans suggestion can be described as "update the contents of an existing file" so old permissions and hard links still point to that file.
"Update the contents" seems much closer to the expected behavior of an editor than does "write a new file", so its good from that point of view.
But from an efficiency point of view its much more work. Probably not a problem on a local filesystem, but on a remote filesystem it requires three transfers of the data instead of one, read the old file and write the backup then write the new file. As I only use remote filesystems on fast networks I can't say how important this is likely to be, but for big files/lots of files it may be a problem, also I'm thinking web sites edited via ftp, ssh etc. This seems to be the use case for most of the performance complaints.
If making a backup file is selected when the file is opened then the write of the backup happens then, uses the data read for the open and doesn't need to happen at save time, it could even be asynchronous so long as it was checked for correct completion before saving. This would reduce the user visible performance impact.
Personally I would implement both and let the user choose (especially as g_file_set_contents exists).
Cheers Lex
Perhaps you might like to file a bug against GIO. Perhaps first use gdb to break on that function just to be absolutely sure.
Perhaps. But bugs filed to gnome and kde may take years to resolve...
...but if nobody files them, they are likely to never be fixed.
Regards, Colomban _______________________________________________ Geany-devel mailing list Geany-devel@uvena.de http://lists.uvena.de/cgi-bin/mailman/listinfo/geany-devel