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authorVlad Apostolov <vapo@sgi.com>2007-08-28 14:00:28 +1000
committerTim Shimmin <tes@chook.melbourne.sgi.com>2007-10-15 16:53:36 +1000
commitb93bd20cd59eb7ec172f95d08b100fea688d8bcf (patch)
tree9ce717b59f657e0a7047f099921b28f43faa617f /fs/xfs/xfs_attr.h
parentda353b0d64e070ae7c5342a0d56ec20ae9ef5cfb (diff)
[XFS] do not have XFSMNT_IDELETE as default when mounted with XFSMNT_DMAPI
XFS inodes are dynamically allocated on demand, rather than being allocated at mkfs time. Chunks of 64 inodes are allocated at once, but they are never freed. Over time, this can lead to filesystem fragmentation, clusters of inodes and the btrees which point at them can be scattered around the system. By freeing clusters as they are emptied, we will reduce fragmentation of the free space after removing files. This in turn will allow us to make better placement decisions when repopulating a filesystem. The XFSMNT_IDELETE mount option enables freeing clusters when they get empty. Unfortunately a side effect of freeing inode clusters is that the inode generation numbers of such inodes would be reset to zero when the cluster is reclaimed. This is a problem in particular for a DMAPI enabled filesystem as the the DMAPI handles need to be unique and persistent in time. An unique DMAPI handle is built with the help of the inode generation number. When the last one is prematurely reset by an inode cluster reclaim, there is a high probability of different generation inodes to end up having identical DMAPI handles. To avoid the problem with identical DMAPI handles, the XFSMNT_IDELETE mount option should be set as default, only if the filesystem is not mounted with XFSMNT_DMAPI. SGI-PV: 969192 SGI-Modid: xfs-linux-melb:xfs-kern:29486a Signed-off-by: Vlad Apostolov <vapo@sgi.com> Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Mark Goodwin <markgw@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com>
Diffstat (limited to 'fs/xfs/xfs_attr.h')
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