Feature/patch request

[Bucher, Dr. Damian]

Hi,

we ran into a problem, while using filesystem snapshots on a GPFS-filesystem. With this we want to give the users the opportunity to restore Mailboxes from this snapshots in case they deleted mail by accident.

For each snapshot we create a namespace via a postlogin skript (with INDEX=MEMORY to avoid writing index files to a ro filesystem). The snapshot are of course read only.
When accessing the mailboxes in the namespaces, dovecot generates an error (ro filesystem):
Error: Mailbox #backup20/Mail/deleted-messages: open() failed with mbox: Read-only file system


We tracked that down to a problem in src/lib-storage/index/mbox/mbox-file.c (yes, we are still using mbox ;) )

fd = open(mailbox_get_path(&mbox->box),
                  mbox_is_backend_readonly(mbox) ? O_RDONLY : O_RDWR);
        if (fd == -1 && errno == EACCES && !mbox->backend_readonly) {
                mbox->backend_readonly = TRUE;
                fd = open(mailbox_get_path(&mbox->box), O_RDONLY);
        }

Here the mailbox is opened and it is checked wether the file is ro or rw.
Since the snapshot contains the original file permissions, the file is of course rw, but the filesystem is ro.
Unfortunately the code only checks for file permissions (errno == EACCES), which doesn’t catch our error condition (FS ro).

We think that exchanging this to (errno == EACCESS || errno == EROFS) would catch the file system ro error correctly and set the readonly flag correctly and open the mailbox ro.
(this probably hast to be done for other mailbox formats in the corresponding files too)

What do you think? Is there a chance to implement that in an upcoming release?

Best regards
Damian

— 
Postmaster at WWU
WWU IT
Westfälische Wilhelms-Universität (WWU) Münster
Röntgenstr. 7-13, 48149 Münster

mailto:postmaster at uni-muenster.de





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