xfs: split xfs_itruncate_finish

Split the guts of xfs_itruncate_finish that loop over the existing extents
and calls xfs_bunmapi on them into a new helper, xfs_itruncate_externs.
Make xfs_attr_inactive call it directly instead of xfs_itruncate_finish,
which allows to simplify the latter a lot, by only letting it deal with
the data fork.  As a result xfs_itruncate_finish is renamed to
xfs_itruncate_data to make its use case more obvious.

Also remove the sync parameter from xfs_itruncate_data, which has been
unessecary since the introduction of the busy extent list in 2002, and
completely dead code since 2003 when the XFS_BMAPI_ASYNC parameter was
made a no-op.

I can't actually see why the xfs_attr_inactive needs to set the transaction
sync, but let's keep this patch simple and without changes in behaviour.

Also avoid passing a useless argument to xfs_isize_check, and make it
private to xfs_inode.c.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

1 files changed, 128 insertions, 229 deletions

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 82a282ab63dc..aa143b870afb 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -52,7 +52,7 @@ kmem_zone_t *xfs_ifork_zone;
 kmem_zone_t *xfs_inode_zone;
 
 /*
- * Used in xfs_itruncate().  This is the maximum number of extents
+ * Used in xfs_itruncate_extents().  This is the maximum number of extents
  * freed from a file in a single transaction.
  */
 #define XFS_ITRUNC_MAX_EXTENTS  2
@@ -1179,15 +1179,15 @@ xfs_ialloc(
  * at least do it for regular files.
  */
 #ifdef DEBUG
-void
+STATIC void
 xfs_isize_check(
-        xfs_mount_t     *mp,
-        xfs_inode_t     *ip,
-        xfs_fsize_t     isize)
+        struct xfs_inode        *ip,
+        xfs_fsize_t             isize)
 {
-        xfs_fileoff_t   map_first;
-        int             nimaps;
-        xfs_bmbt_irec_t imaps[2];
+        struct xfs_mount        *mp = ip->i_mount;
+        xfs_fileoff_t           map_first;
+        int                     nimaps;
+        xfs_bmbt_irec_t         imaps[2];
 
         if ((ip->i_d.di_mode & S_IFMT) != S_IFREG)
                 return;
@@ -1214,11 +1214,14 @@ xfs_isize_check(
         ASSERT(nimaps == 1);
         ASSERT(imaps[0].br_startblock == HOLESTARTBLOCK);
 }
+#else   /* DEBUG */
+#define xfs_isize_check(ip, isize)
 #endif  /* DEBUG */
 
 /*
- * Free up the underlying blocks past new_size.  The new size must be
- * smaller than the current size.
+ * Free up the underlying blocks past new_size.  The new size must be smaller
+ * than the current size.  This routine can be used both for the attribute and
+ * data fork, and does not modify the inode size, which is left to the caller.
  *
  * The transaction passed to this routine must have made a permanent log
  * reservation of at least XFS_ITRUNCATE_LOG_RES.  This routine may commit the
@@ -1230,31 +1233,6 @@ xfs_isize_check(
  * will be "held" within the returned transaction.  This routine does NOT
  * require any disk space to be reserved for it within the transaction.
  *
- * The fork parameter must be either XFS_ATTR_FORK or XFS_DATA_FORK, and it
- * indicates the fork which is to be truncated.  For the attribute fork we only
- * support truncation to size 0.
- *
- * We use the sync parameter to indicate whether or not the first transaction
- * we perform might have to be synchronous.  For the attr fork, it needs to be
- * so if the unlink of the inode is not yet known to be permanent in the log.
- * This keeps us from freeing and reusing the blocks of the attribute fork
- * before the unlink of the inode becomes permanent.
- *
- * For the data fork, we normally have to run synchronously if we're being
- * called out of the inactive path or we're being called out of the create path
- * where we're truncating an existing file.  Either way, the truncate needs to
- * be sync so blocks don't reappear in the file with altered data in case of a
- * crash.  wsync filesystems can run the first case async because anything that
- * shrinks the inode has to run sync so by the time we're called here from
- * inactive, the inode size is permanently set to 0.
- *
- * Calls from the truncate path always need to be sync unless we're in a wsync
- * filesystem and the file has already been unlinked.
- *
- * The caller is responsible for correctly setting the sync parameter.  It gets
- * too hard for us to guess here which path we're being called out of just
- * based on inode state.
- *
  * If we get an error, we must return with the inode locked and linked into the
  * current transaction. This keeps things simple for the higher level code,
  * because it always knows that the inode is locked and held in the transaction
@@ -1262,124 +1240,31 @@ xfs_isize_check(
  * dirty on error so that transactions can be easily aborted if possible.
  */
 int
-xfs_itruncate_finish(
-        xfs_trans_t     **tp,
-        xfs_inode_t     *ip,
-        xfs_fsize_t     new_size,
-        int             fork,
-        int             sync)
+xfs_itruncate_extents(
+        struct xfs_trans        **tpp,
+        struct xfs_inode        *ip,
+        int                     whichfork,
+        xfs_fsize_t             new_size)
 {
-        xfs_fsblock_t   first_block;
-        xfs_fileoff_t   first_unmap_block;
-        xfs_fileoff_t   last_block;
-        xfs_filblks_t   unmap_len=0;
-        xfs_mount_t     *mp;
-        xfs_trans_t     *ntp;
-        int             done;
-        int             committed;
-        xfs_bmap_free_t free_list;
-        int             error;
+        struct xfs_mount        *mp = ip->i_mount;
+        struct xfs_trans        *tp = *tpp;
+        struct xfs_trans        *ntp;
+        xfs_bmap_free_t         free_list;
+        xfs_fsblock_t           first_block;
+        xfs_fileoff_t           first_unmap_block;
+        xfs_fileoff_t           last_block;
+        xfs_filblks_t           unmap_len;
+        int                     committed;
+        int                     error = 0;
+        int                     done = 0;
 
         ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_IOLOCK_EXCL));
-        ASSERT((new_size == 0) || (new_size <= ip->i_size));
-        ASSERT(*tp != NULL);
-        ASSERT((*tp)->t_flags & XFS_TRANS_PERM_LOG_RES);
-        ASSERT(ip->i_transp == *tp);
+        ASSERT(new_size <= ip->i_size);
+        ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES);
+        ASSERT(ip->i_transp == tp);
         ASSERT(ip->i_itemp != NULL);
         ASSERT(ip->i_itemp->ili_lock_flags == 0);
-
-
-        ntp = *tp;
-        mp = (ntp)->t_mountp;
-        ASSERT(! XFS_NOT_DQATTACHED(mp, ip));
-
-        /*
-         * We only support truncating the entire attribute fork.
-         */
-        if (fork == XFS_ATTR_FORK) {
-                new_size = 0LL;
-        }
-        first_unmap_block = XFS_B_TO_FSB(mp, (xfs_ufsize_t)new_size);
-        trace_xfs_itruncate_finish_start(ip, new_size);
-
-        /*
-         * The first thing we do is set the size to new_size permanently
-         * on disk.  This way we don't have to worry about anyone ever
-         * being able to look at the data being freed even in the face
-         * of a crash.  What we're getting around here is the case where
-         * we free a block, it is allocated to another file, it is written
-         * to, and then we crash.  If the new data gets written to the
-         * file but the log buffers containing the free and reallocation
-         * don't, then we'd end up with garbage in the blocks being freed.
-         * As long as we make the new_size permanent before actually
-         * freeing any blocks it doesn't matter if they get written to.
-         *
-         * The callers must signal into us whether or not the size
-         * setting here must be synchronous.  There are a few cases
-         * where it doesn't have to be synchronous.  Those cases
-         * occur if the file is unlinked and we know the unlink is
-         * permanent or if the blocks being truncated are guaranteed
-         * to be beyond the inode eof (regardless of the link count)
-         * and the eof value is permanent.  Both of these cases occur
-         * only on wsync-mounted filesystems.  In those cases, we're
-         * guaranteed that no user will ever see the data in the blocks
-         * that are being truncated so the truncate can run async.
-         * In the free beyond eof case, the file may wind up with
-         * more blocks allocated to it than it needs if we crash
-         * and that won't get fixed until the next time the file
-         * is re-opened and closed but that's ok as that shouldn't
-         * be too many blocks.
-         *
-         * However, we can't just make all wsync xactions run async
-         * because there's one call out of the create path that needs
-         * to run sync where it's truncating an existing file to size
-         * 0 whose size is > 0.
-         *
-         * It's probably possible to come up with a test in this
-         * routine that would correctly distinguish all the above
-         * cases from the values of the function parameters and the
-         * inode state but for sanity's sake, I've decided to let the
-         * layers above just tell us.  It's simpler to correctly figure
-         * out in the layer above exactly under what conditions we
-         * can run async and I think it's easier for others read and
-         * follow the logic in case something has to be changed.
-         * cscope is your friend -- rcc.
-         *
-         * The attribute fork is much simpler.
-         *
-         * For the attribute fork we allow the caller to tell us whether
-         * the unlink of the inode that led to this call is yet permanent
-         * in the on disk log.  If it is not and we will be freeing extents
-         * in this inode then we make the first transaction synchronous
-         * to make sure that the unlink is permanent by the time we free
-         * the blocks.
-         */
-        if (fork == XFS_DATA_FORK) {
-                if (ip->i_d.di_nextents > 0) {
-                        /*
-                         * If we are not changing the file size then do
-                         * not update the on-disk file size - we may be
-                         * called from xfs_inactive_free_eofblocks().  If we
-                         * update the on-disk file size and then the system
-                         * crashes before the contents of the file are
-                         * flushed to disk then the files may be full of
-                         * holes (ie NULL files bug).
-                         */
-                        if (ip->i_size != new_size) {
-                                ip->i_d.di_size = new_size;
-                                ip->i_size = new_size;
-                                xfs_trans_log_inode(ntp, ip, XFS_ILOG_CORE);
-                        }
-                }
-        } else if (sync) {
-                ASSERT(!(mp->m_flags & XFS_MOUNT_WSYNC));
-                if (ip->i_d.di_anextents > 0)
-                        xfs_trans_set_sync(ntp);
-        }
-        ASSERT(fork == XFS_DATA_FORK ||
-                (fork == XFS_ATTR_FORK &&
-                        ((sync && !(mp->m_flags & XFS_MOUNT_WSYNC)) ||
-                         (sync == 0 && (mp->m_flags & XFS_MOUNT_WSYNC)))));
+        ASSERT(!XFS_NOT_DQATTACHED(mp, ip));
 
         /*
          * Since it is possible for space to become allocated beyond
@@ -1390,128 +1275,142 @@ xfs_itruncate_finish(
          * beyond the maximum file size (ie it is the same as last_block),
          * then there is nothing to do.
          */
+        first_unmap_block = XFS_B_TO_FSB(mp, (xfs_ufsize_t)new_size);
         last_block = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_MAXIOFFSET(mp));
-        ASSERT(first_unmap_block <= last_block);
-        done = 0;
-        if (last_block == first_unmap_block) {
-                done = 1;
-        } else {
-                unmap_len = last_block - first_unmap_block + 1;
-        }
+        if (first_unmap_block == last_block)
+                return 0;
+
+        ASSERT(first_unmap_block < last_block);
+        unmap_len = last_block - first_unmap_block + 1;
         while (!done) {
-                /*
-                 * Free up up to XFS_ITRUNC_MAX_EXTENTS.  xfs_bunmapi()
-                 * will tell us whether it freed the entire range or
-                 * not.  If this is a synchronous mount (wsync),
-                 * then we can tell bunmapi to keep all the
-                 * transactions asynchronous since the unlink
-                 * transaction that made this inode inactive has
-                 * already hit the disk.  There's no danger of
-                 * the freed blocks being reused, there being a
-                 * crash, and the reused blocks suddenly reappearing
-                 * in this file with garbage in them once recovery
-                 * runs.
-                 */
                 xfs_bmap_init(&free_list, &first_block);
-                error = xfs_bunmapi(ntp, ip,
+                error = xfs_bunmapi(tp, ip,
                                     first_unmap_block, unmap_len,
-                                    xfs_bmapi_aflag(fork),
+                                    xfs_bmapi_aflag(whichfork),
                                     XFS_ITRUNC_MAX_EXTENTS,
                                     &first_block, &free_list,
                                     &done);
-                if (error) {
-                        /*
-                         * If the bunmapi call encounters an error,
-                         * return to the caller where the transaction
-                         * can be properly aborted.  We just need to
-                         * make sure we're not holding any resources
-                         * that we were not when we came in.
-                         */
-                        xfs_bmap_cancel(&free_list);
-                        return error;
-                }
+                if (error)
+                        goto out_bmap_cancel;
 
                 /*
                  * Duplicate the transaction that has the permanent
                  * reservation and commit the old transaction.
                  */
-                error = xfs_bmap_finish(tp, &free_list, &committed);
-                ntp = *tp;
+                error = xfs_bmap_finish(&tp, &free_list, &committed);
                 if (committed)
-                        xfs_trans_ijoin(ntp, ip);
-
-                if (error) {
-                        /*
-                         * If the bmap finish call encounters an error, return
-                         * to the caller where the transaction can be properly
-                         * aborted.  We just need to make sure we're not
-                         * holding any resources that we were not when we came
-                         * in.
-                         *
-                         * Aborting from this point might lose some blocks in
-                         * the file system, but oh well.
-                         */
-                        xfs_bmap_cancel(&free_list);
-                        return error;
-                }
+                        xfs_trans_ijoin(tp, ip);
+                if (error)
+                        goto out_bmap_cancel;
 
                 if (committed) {
                         /*
                          * Mark the inode dirty so it will be logged and
                          * moved forward in the log as part of every commit.
                          */
-                        xfs_trans_log_inode(ntp, ip, XFS_ILOG_CORE);
+                        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
                 }
 
-                ntp = xfs_trans_dup(ntp);
-                error = xfs_trans_commit(*tp, 0);
-                *tp = ntp;
+                ntp = xfs_trans_dup(tp);
+                error = xfs_trans_commit(tp, 0);
+                tp = ntp;
 
-                xfs_trans_ijoin(ntp, ip);
+                xfs_trans_ijoin(tp, ip);
 
                 if (error)
-                        return error;
+                        goto out;
+
                 /*
-                 * transaction commit worked ok so we can drop the extra ticket
+                 * Transaction commit worked ok so we can drop the extra ticket
                  * reference that we gained in xfs_trans_dup()
                  */
-                xfs_log_ticket_put(ntp->t_ticket);
-                error = xfs_trans_reserve(ntp, 0,
+                xfs_log_ticket_put(tp->t_ticket);
+                error = xfs_trans_reserve(tp, 0,
                                         XFS_ITRUNCATE_LOG_RES(mp), 0,
                                         XFS_TRANS_PERM_LOG_RES,
                                         XFS_ITRUNCATE_LOG_COUNT);
                 if (error)
-                        return error;
+                        goto out;
         }
+
+out:
+        *tpp = tp;
+        return error;
+out_bmap_cancel:
         /*
-         * Only update the size in the case of the data fork, but
-         * always re-log the inode so that our permanent transaction
-         * can keep on rolling it forward in the log.
+         * If the bunmapi call encounters an error, return to the caller where
+         * the transaction can be properly aborted.  We just need to make sure
+         * we're not holding any resources that we were not when we came in.
          */
-        if (fork == XFS_DATA_FORK) {
-                xfs_isize_check(mp, ip, new_size);
+        xfs_bmap_cancel(&free_list);
+        goto out;
+}
+
+int
+xfs_itruncate_data(
+        struct xfs_trans        **tpp,
+        struct xfs_inode        *ip,
+        xfs_fsize_t             new_size)
+{
+        int                     error;
+
+        trace_xfs_itruncate_data_start(ip, new_size);
+
+        /*
+         * The first thing we do is set the size to new_size permanently on
+         * disk.  This way we don't have to worry about anyone ever being able
+         * to look at the data being freed even in the face of a crash.
+         * What we're getting around here is the case where we free a block, it
+         * is allocated to another file, it is written to, and then we crash.
+         * If the new data gets written to the file but the log buffers
+         * containing the free and reallocation don't, then we'd end up with
+         * garbage in the blocks being freed.  As long as we make the new_size
+         * permanent before actually freeing any blocks it doesn't matter if
+         * they get written to.
+         */
+        if (ip->i_d.di_nextents > 0) {
                 /*
-                 * If we are not changing the file size then do
-                 * not update the on-disk file size - we may be
-                 * called from xfs_inactive_free_eofblocks().  If we
-                 * update the on-disk file size and then the system
-                 * crashes before the contents of the file are
-                 * flushed to disk then the files may be full of
-                 * holes (ie NULL files bug).
+                 * If we are not changing the file size then do not update
+                 * the on-disk file size - we may be called from
+                 * xfs_inactive_free_eofblocks().  If we update the on-disk
+                 * file size and then the system crashes before the contents
+                 * of the file are flushed to disk then the files may be
+                 * full of holes (ie NULL files bug).
                  */
                 if (ip->i_size != new_size) {
                         ip->i_d.di_size = new_size;
                         ip->i_size = new_size;
+                        xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
                 }
         }
-        xfs_trans_log_inode(ntp, ip, XFS_ILOG_CORE);
-        ASSERT((new_size != 0) ||
-               (fork == XFS_ATTR_FORK) ||
-               (ip->i_delayed_blks == 0));
-        ASSERT((new_size != 0) ||
-               (fork == XFS_ATTR_FORK) ||
-               (ip->i_d.di_nextents == 0));
-        trace_xfs_itruncate_finish_end(ip, new_size);
+
+        error = xfs_itruncate_extents(tpp, ip, XFS_DATA_FORK, new_size);
+        if (error)
+                return error;
+
+        /*
+         * If we are not changing the file size then do not update the on-disk
+         * file size - we may be called from xfs_inactive_free_eofblocks().
+         * If we update the on-disk file size and then the system crashes
+         * before the contents of the file are flushed to disk then the files
+         * may be full of holes (ie NULL files bug).
+         */
+        xfs_isize_check(ip, new_size);
+        if (ip->i_size != new_size) {
+                ip->i_d.di_size = new_size;
+                ip->i_size = new_size;
+        }
+
+        ASSERT(new_size != 0 || ip->i_delayed_blks == 0);
+        ASSERT(new_size != 0 || ip->i_d.di_nextents == 0);
+
+        /*
+         * Always re-log the inode so that our permanent transaction can keep
+         * on rolling it forward in the log.
+         */
+        xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
+
+        trace_xfs_itruncate_data_end(ip, new_size);
         return 0;
 }