https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233245
Bug ID: 233245
Summary: [UFS] Softupdates fails to track dependency between
appended data and i_size
Product: Base System
Version: CURRENT
Hardware: Any
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: kern
Assignee: [email protected]
Reporter: [email protected]
This manifests with recently appended files containing extraneous zero data at
the end of the file after power loss or crash.
Detection of append could happen in either ffs_balloc_ufs[12] (which is where
most softdep dependencies seem to be added, and which is called unconditionally
by ffs_write()) in the several "happy" cases where we discover we do not need
to actually allocate a new block, e.g., cases like:
753 if (lbn < UFS_NDADDR) {
...
756 nb = dp->di_db[lbn];
757 if (nb != 0 && ip->i_size >= smalllblktosize(fs, lbn +
1)) {
758 error = bread_gb(vp, lbn, fs->fs_bsize, NOCRED,
759 gbflags, &bp);
...
764 bp->b_blkno = fsbtodb(fs, nb);
+++ if (DOINGSOFTDEP(vp) && startoffset + size >
ip->i_size)
+++ softdep_setup_append(...);
765 *bpp = bp;
766 return (0);
It could also just be checked in a single location in ffs_write() itself:
754 for (error = 0; uio->uio_resid > 0;) {
755 lbn = lblkno(fs, uio->uio_offset);
756 blkoffset = blkoff(fs, uio->uio_offset);
...
781 if (uio->uio_offset + xfersize > ip->i_size) {
+++ if (DOINGSOFTDEP(vp))
+++ softdep_setup_append(...);
782 ip->i_size = uio->uio_offset + xfersize;
783 DIP_SET(ip, i_size, ip->i_size);
784 }
Append data could probably be tracked in quite similar fashion to diradd
(directory entry adds).
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