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authorTomohiro Kusumi <kusumi.tomohiro@gmail.com>2019-05-08 02:06:30 +0900
committerBrian Behlendorf <behlendorf1@llnl.gov>2019-05-07 10:06:30 -0700
commit9c53e51616c99592973ebf94b4fd54a5f8c8756d (patch)
tree7e1b9d39cebc8fdb7a4b4fc9f3853b79b122c196 /README.md
parent75346937de39f059722eedd29468ac9b86bea67c (diff)
Fix `zfs set atime|relatime=off|on` behavior on inherited datasets
`zfs set atime|relatime=off|on` doesn't disable or enable the property on read for datasets whose property was inherited from parent, until a dataset is once unmounted and mounted again. (The properties start to work properly if a dataset is once unmounted and mounted again. The difference comes from regular mount process, e.g. via zpool import, uses mount options based on properties read from ondisk layout for each dataset, whereas `zfs set atime|relatime=off|on` just remounts a specified dataset.) -- # zpool create p1 <device> # zfs create p1/f1 # zfs set atime=off p1 # echo test > /p1/f1/test # sync # zfs list NAME USED AVAIL REFER MOUNTPOINT p1 176K 18.9G 25.5K /p1 p1/f1 26K 18.9G 26K /p1/f1 # zfs get atime NAME PROPERTY VALUE SOURCE p1 atime off local p1/f1 atime off inherited from p1 # stat /p1/f1/test | grep Access | tail -1 Access: 2019-04-26 23:32:33.741205192 +0900 # cat /p1/f1/test test # stat /p1/f1/test | grep Access | tail -1 Access: 2019-04-26 23:32:50.173231861 +0900 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ changed by read(2) -- The problem is that zfsvfs::z_atime which was probably intended to keep incore atime state just gets updated by a callback function of "atime" property change, atime_changed_cb(), and never used for anything else. Since now that all file read and atime update use a common function zpl_iter_read_common() -> file_accessed(), and whether to update atime via ->dirty_inode() is determined by atime_needs_update(), atime_needs_update() needs to return false once atime is turned off. It currently continues to return true on `zfs set atime=off`. Fix atime_changed_cb() by setting or dropping SB_NOATIME in VFS super block depending on a new atime value, so that atime_needs_update() works as expected after property change. The same problem applies to "relatime" except that a self contained relatime test is needed. This is because relatime_need_update() is based on a mount option flag MNT_RELATIME, which doesn't exist in datasets with inherited "relatime" property via `zfs set relatime=...`, hence it needs its own relatime test zfs_relatime_need_update(). Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@gmail.com> Closes #8674 Closes #8675
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