From: Jan Kara Subject: Update documentation of mount(8) about barrier mount options Signed-off-by: Jan Kara Index: util-linux-2.24.1/sys-utils/mount.8 =================================================================== --- util-linux-2.24.1.orig/sys-utils/mount.8 +++ util-linux-2.24.1/sys-utils/mount.8 @@ -1524,12 +1524,13 @@ ordered mode. Abort the journal if an error occurs in a file data buffer in ordered mode. .TP .BR barrier=0 " / " barrier=1 " -This enables/disables barriers. barrier=0 disables it, barrier=1 enables it. -Write barriers enforce proper on-disk ordering of journal commits, making -volatile disk write caches safe to use, at some performance penalty. The ext3 -filesystem does not enable write barriers by default. Be sure to enable -barriers unless your disks are battery-backed one way or another. Otherwise -you risk filesystem corruption in case of power failure. +This disables / enables the use of write barriers in the jbd code. barrier=0 +disables, barrier=1 enables (default). This also requires an IO stack which can +support barriers, and if jbd gets an error on a barrier write, it will disable +barriers again with a warning. Write barriers enforce proper on-disk ordering +of journal commits, making volatile disk write caches safe to use, at some +performance penalty. If your disks are battery-backed in one way or another, +disabling barriers may safely improve performance. .TP .BI commit= nrsec Sync all data and metadata every @@ -1577,15 +1578,9 @@ enabled older kernels cannot mount the d This will enable 'journal_checksum' internally. .TP .BR barrier=0 " / " barrier=1 " / " barrier " / " nobarrier -This enables/disables the use of write barriers in the jbd code. barrier=0 -disables, barrier=1 enables. This also requires an IO stack which can support -barriers, and if jbd gets an error on a barrier write, it will disable again -with a warning. Write barriers enforce proper on-disk ordering of journal -commits, making volatile disk write caches safe to use, at some performance -penalty. If your disks are battery-backed in one way or another, disabling -barriers may safely improve performance. The mount options "barrier" and -"nobarrier" can also be used to enable or disable barriers, for consistency -with other ext4 mount options. +These mount options have the same effect as in ext3. The mount options +"barrier" and "nobarrier" are added for consistency with other ext4 mount +options. The ext4 filesystem enables write barriers by default. .TP @@ -2266,13 +2261,13 @@ Enable POSIX Access Control Lists. See t manual page. .TP .BR barrier=none " / " barrier=flush " -This enables/disables the use of write barriers in the journaling code. -barrier=none disables it, barrier=flush enables it. Write barriers enforce +This disables / enables the use of write barriers in the journaling code. +barrier=none disables, barrier=flush enables (default). This also requires an +IO stack which can support barriers, and if reiserfs gets an error on a barrier +write, it will disable barriers again with a warning. Write barriers enforce proper on-disk ordering of journal commits, making volatile disk write caches -safe to use, at some performance penalty. The reiserfs filesystem does not -enable write barriers by default. Be sure to enable barriers unless your disks -are battery-backed one way or another. Otherwise you risk filesystem -corruption in case of power failure. +safe to use, at some performance penalty. If your disks are battery-backed in +one way or another, disabling barriers may safely improve performance. .SH "Mount options for romfs" None. Index: util-linux-2.24.1/mount-deprecated/mount.8 =================================================================== --- util-linux-2.24.1.orig/mount-deprecated/mount.8 +++ util-linux-2.24.1/mount-deprecated/mount.8 @@ -1389,12 +1389,13 @@ in files after a crash and journal recov .RE .TP .BR barrier=0 " / " barrier=1 " -This enables/disables barriers. barrier=0 disables it, barrier=1 enables it. -Write barriers enforce proper on-disk ordering of journal commits, making -volatile disk write caches safe to use, at some performance penalty. The ext3 -filesystem does not enable write barriers by default. Be sure to enable -barriers unless your disks are battery-backed one way or another. Otherwise -you risk filesystem corruption in case of power failure. +This disables / enables the use of write barriers in the jbd code. barrier=0 +disables, barrier=1 enables (default). This also requires an IO stack which can +support barriers, and if jbd gets an error on a barrier write, it will disable +barriers again with a warning. Write barriers enforce proper on-disk ordering +of journal commits, making volatile disk write caches safe to use, at some +performance penalty. If your disks are battery-backed in one way or another, +disabling barriers may safely improve performance. .TP .BI commit= nrsec Sync all data and metadata every @@ -1433,15 +1434,9 @@ enabled older kernels cannot mount the d This will enable 'journal_checksum' internally. .TP .BR barrier=0 " / " barrier=1 " / " barrier " / " nobarrier -This enables/disables the use of write barriers in the jbd code. barrier=0 -disables, barrier=1 enables. This also requires an IO stack which can support -barriers, and if jbd gets an error on a barrier write, it will disable again -with a warning. Write barriers enforce proper on-disk ordering of journal -commits, making volatile disk write caches safe to use, at some performance -penalty. If your disks are battery-backed in one way or another, disabling -barriers may safely improve performance. The mount options "barrier" and -"nobarrier" can also be used to enable or disable barriers, for consistency -with other ext4 mount options. +These mount options have the same effect as in ext3. The mount options +"barrier" and "nobarrier" are added for consistency with other ext4 mount +options. The ext4 filesystem enables write barriers by default. .TP @@ -2099,13 +2094,13 @@ Enable POSIX Access Control Lists. See t manual page. .TP .BR barrier=none " / " barrier=flush " -This enables/disables the use of write barriers in the journaling code. -barrier=none disables it, barrier=flush enables it. Write barriers enforce +This disables / enables the use of write barriers in the journaling code. +barrier=none disables, barrier=flush enables (default). This also requires an +IO stack which can support barriers, and if reiserfs gets an error on a barrier +write, it will disable barriers again with a warning. Write barriers enforce proper on-disk ordering of journal commits, making volatile disk write caches -safe to use, at some performance penalty. The reiserfs filesystem does not -enable write barriers by default. Be sure to enable barriers unless your disks -are battery-backed one way or another. Otherwise you risk filesystem -corruption in case of power failure. +safe to use, at some performance penalty. If your disks are battery-backed in +one way or another, disabling barriers may safely improve performance. .SH "Mount options for romfs" None.