fs/jfs: TRIM support for JFS Filesystem

This patch adds support for the two linux interfaces of the discard/TRIM
command for SSD devices and sparse/thinly-provisioned LUNs.

JFS will support batched discard via FITRIM ioctl and online discard
with the discard mount option.

Signed-off-by: Tino Reichardt <list-jfs@mcmilk.de>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>

1 files changed, 16 insertions, 3 deletions

diff --git a/Documentation/filesystems/jfs.txt b/Documentation/filesystems/jfs.txt
index 26ebde77e821..2f94f9ca1794 100644
--- a/Documentation/filesystems/jfs.txt
+++ b/Documentation/filesystems/jfs.txt
@@ -3,6 +3,7 @@ IBM's Journaled File System (JFS) for Linux
 JFS Homepage:  http://jfs.sourceforge.net/
 
 The following mount options are supported:
+(*) == default
 
 iocharset=name  Character set to use for converting from Unicode to
                 ASCII.  The default is to do no conversion.  Use
@@ -21,12 +22,12 @@ nointegrity	Do not write to the journal.  The primary use of this option
                 from backup media.  The integrity of the volume is not
                 guaranteed if the system abnormally abends.
 
-integrity       Default.  Commit metadata changes to the journal.  Use this
-                option to remount a volume where the nointegrity option was
+integrity(*)    Commit metadata changes to the journal.  Use this option to
+                remount a volume where the nointegrity option was
                 previously specified in order to restore normal behavior.
 
 errors=continue         Keep going on a filesystem error.
-errors=remount-ro       Default. Remount the filesystem read-only on an error.
+errors=remount-ro(*)    Remount the filesystem read-only on an error.
 errors=panic            Panic and halt the machine if an error occurs.
 
 uid=value       Override on-disk uid with specified value
@@ -35,6 +36,18 @@ umask=value	Override on-disk umask with specified octal value.  For
                 directories, the execute bit will be set if the corresponding
                 read bit is set.
 
+discard=minlen  This enables/disables the use of discard/TRIM commands.
+discard         The discard/TRIM commands are sent to the underlying
+nodiscard(*)    block device when blocks are freed. This is useful for SSD
+                devices and sparse/thinly-provisioned LUNs.  The FITRIM ioctl
+                command is also available together with the nodiscard option.
+                The value of minlen specifies the minimum blockcount, when
+                a TRIM command to the block device is considered usefull.
+                When no value is given to the discard option, it defaults to
+                64 blocks, which means 256KiB in JFS.
+                The minlen value of discard overrides the minlen value given
+                on an FITRIM ioctl().
+
 Please send bugs, comments, cards and letters to shaggy@linux.vnet.ibm.com.
 
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