files at once on a filesystem running soft updates. The root of
the problem is that soft updates limits the amount of memory that
may be allocated to dependency structures so as to avoid hogging
kernel memory. The original algorithm just waited for the disk I/O
to catch up and reduce the number of dependencies. This new code
takes a much more aggressive approach. Basically there are two
resources that routinely hit the limit. Inode dependencies during
periods with a high file creation rate and file and block removal
dependencies during periods with a high file removal rate. I have
attacked these problems from two fronts. When the inode dependency
limits are reached, I pick a random inode dependency, UFS_UPDATE
it together with all the other dirty inodes contained within its
disk block and then write that disk block. This trick usually
clears 5-50 inode dependencies in a single disk I/O. For block and
file removal dependencies, I pick a random directory page that has
at least one remove pending and VOP_FSYNC its directory. That
releases all its removal dependencies to the work queue. To further
hasten things along, I also immediately start the work queue process
rather than waiting for its next one second scheduled run.
turns out to not be useful to unwind the dependencies and continue in
the face of a fatal error.
Also changed the log() to a printf() in softdep_error() so that it will
be output in the case of a impending panic.
Submitted by: Kirk McKusick <mckusick@mckusick.com>
MNT_WAIT when we mean boolean `true' or check for that value not being
passed. There was no problem in practice because MNT_WAIT had the
magic value of 1.
The problem is caused when a directory block is compacted. When this
occurs, softdep_change_directoryentry_offset() is called to relocate each
directory entry and adjust its matching diradd structure, if any, to match
the new location of the entry. The bug is that while
softdep_change_directoryentry_offset() correctly adjusts the offsets of
the diradd structures on the pd_diraddhd[] lists (which are not yet ready
to be committed to disk), it fails to adjust the offsets of the diradd
structures on the pd_pendinghd list (which are ready to be committed to
disk). This causes the dependency structures to be inconsistent with
the buf contents. Now, if the compaction has moved a directory entry to
the same offset as one of the diradd structures on the pd_pendinghd list
*and* a syscall is done that tries to remove this directory entry before
this directory block has been written to disk (which would empty
pd_pendinghd), a sanity check in newdirrem() will call panic() when it
notices that the inode number in the entry that it is to be removed doesn't
match the inode number in the diradd structure with that offset of that
entry.
Reviewed by: Kirk McKusick <mckusick@McKusick.COM>
Submitted by: Don Lewis <Don.Lewis@tsc.tdk.com>
Submitted by: Kirk McKusick <mckusick@McKusick.COM>
Two minor changes are also included,
1. Remove gratuitious checks for error return from vn_lock with LK_RETRY set,
vn_lock should always succeed in these cases.
2. Back out change rev. 1.36->1.37, which unnecessarily makes async mount
a little more unstable. It also keeps us in sync with other BSDs.
Suggested by: Bruce Evans <bde@zeta.org.au>
that had an inode that has not yet been written to disk, when the inode of the
new file is also not yet written to disk, and your old directory entry is not
yet on disk but you need to remove it and the new name exists in memory
but has been deleted but the transaction to write the deleted name to disk
exists and has not yet been cancelled by the request to delete the non
existant name. I don't know how kirk could have missed such a glaring
problem for so long. :-) Especially since the inconsitency survived on
the disk for a whole 4 second on average before being fixed by other code.
This was not a crashing bug but just led to filesystem inconsitencies
if you crashed.
Submitted by: Kirk McKusick (mckusick@mckusick.com)
