Messages in this thread | | | Subject | Re: [PATCH v3] exfat: remove EXFAT_SB_DIRTY flag | From | Tetsuhiro Kohada <> | Date | Fri, 10 Jul 2020 16:36:28 +0900 |
| |
On 2020/06/18 22:11, Sungjong Seo wrote: >> BTW >> Even with this patch applied, VOL_DIRTY remains until synced in the above >> case. >> It's not easy to reproduce as rmdir, but I'll try to fix it in the future. > > I think it's not a problem not to clear VOL_DIRTY under real errors, > because VOL_DIRTY is just like a hint to note that write was not finished clearly. > > If you mean there are more situation like ENOTEMPTY you mentioned, > please make new patch to fix them.
When should VOL_DIRTY be cleared?
The current behavior is ...
Case of mkdir, rmdir, rename: - set VOL_DIRTY before operation - set VOL_CLEAN after operating. In async mode, it is actually written to the media after 30 seconds.
Case of cp, touch: - set VOL_DIRTY before operation - however, VOL_CLEAN is not called in this context. VOL_CLEAN will call by sync_fs or unmount.
I added VOL_CLEAN in last of __exfat_write_inode() and exfat_map_cluster(). As a result, VOL_DIRTY is cleared with cp and touch. However, when copying a many files ... - Async mode: VOL_DIRTY is written to the media twice every 30 seconds. - Sync mode: Of course, VOL_DIRTY and VOL_CLEAN to the media for each file.
Frequent writing VOL_DIRTY and VOL_CLEAN increases the risk of boot-sector curruption. If the boot-sector corrupted, it causes the following serious problems on some OSs. - misjudge as unformatted - can't judge as exfat - can't repair
I want to minimize boot sector writes, to reduce these risk.
I looked vfat/udf implementation, which manages similar dirty information on linux, and found that they ware mark-dirty at mount and cleared at unmount.
Here are some ways to clear VOL_DIRTY.
(A) VOL_CLEAN after every write operation. :-) Ejectable at any time after a write operation. :-( Many times write to Boot-sector.
(B) dirty at mount, clear at unmount (same as vfat/udf) :-) Write to boot-sector twice. :-( It remains dirty unless unmounted. :-( Write to boot-sector even if there is no write operation.
(C) dirty on first write operation, clear on unmount :-) Writing to boot-sector is minimal. :-) Will not write to the boot-sector if there is no write operation. :-( It remains dirty unless unmounted.
(D) dirty on first write operation, clear on sync-fs/unmount :-) Writing to boot-sector can be reduced. :-) Will not write to the boot-sector if there is no write operation. :-) sync-fs makes it clean and ejectable immidiately. :-( It remains dirty unless sync-fs or unmount. :-( Frequent sync-fs will increases writes to boot-sector.
I think it should be (C) or(D). What do you think?
BR --- Tetsuhiro Kohada <kohada.t2@gmail.com>
| |