return try_to_free_buffers(page);
}
+/*
+ * When we map a DIO buffer, we may need to attach an ioend that describes the
+ * type of write IO we are doing. This passes to the completion function the
+ * operations it needs to perform. If the mapping is for an overwrite wholly
+ * within the EOF then we don't need an ioend and so we don't allocate one.
+ * This avoids the unnecessary overhead of allocating and freeing ioends for
+ * workloads that don't require transactions on IO completion.
+ *
+ * If we get multiple mappings in a single IO, we might be mapping different
+ * types. But because the direct IO can only have a single private pointer, we
+ * need to ensure that:
+ *
+ * a) i) the ioend spans the entire region of unwritten mappings; or
+ * ii) the ioend spans all the mappings that cross or are beyond EOF; and
+ * b) if it contains unwritten extents, it is *permanently* marked as such
+ *
+ * We could do this by chaining ioends like buffered IO does, but we only
+ * actually get one IO completion callback from the direct IO, and that spans
+ * the entire IO regardless of how many mappings and IOs are needed to complete
+ * the DIO. There is only going to be one reference to the ioend and its life
+ * cycle is constrained by the DIO completion code. hence we don't need
+ * reference counting here.
+ */
+static void
+xfs_map_direct(
+ struct inode *inode,
+ struct buffer_head *bh_result,
+ struct xfs_bmbt_irec *imap,
+ xfs_off_t offset)
+{
+ struct xfs_ioend *ioend;
+ xfs_off_t size = bh_result->b_size;
+ int type;
+
+ if (ISUNWRITTEN(imap))
+ type = XFS_IO_UNWRITTEN;
+ else
+ type = XFS_IO_OVERWRITE;
+
+ trace_xfs_gbmap_direct(XFS_I(inode), offset, size, type, imap);
+
+ if (bh_result->b_private) {
+ ioend = bh_result->b_private;
+ ASSERT(ioend->io_size > 0);
+ ASSERT(offset >= ioend->io_offset);
+ if (offset + size > ioend->io_offset + ioend->io_size)
+ ioend->io_size = offset - ioend->io_offset + size;
+
+ if (type == XFS_IO_UNWRITTEN && type != ioend->io_type)
+ ioend->io_type = XFS_IO_UNWRITTEN;
+
+ trace_xfs_gbmap_direct_update(XFS_I(inode), ioend->io_offset,
+ ioend->io_size, ioend->io_type,
+ imap);
+ } else if (type == XFS_IO_UNWRITTEN ||
+ offset + size > i_size_read(inode)) {
+ ioend = xfs_alloc_ioend(inode, type);
+ ioend->io_offset = offset;
+ ioend->io_size = size;
+
+ bh_result->b_private = ioend;
+ set_buffer_defer_completion(bh_result);
+
+ trace_xfs_gbmap_direct_new(XFS_I(inode), offset, size, type,
+ imap);
+ } else {
+ trace_xfs_gbmap_direct_none(XFS_I(inode), offset, size, type,
+ imap);
+ }
+}
+
+/*
+ * If this is O_DIRECT or the mpage code calling tell them how large the mapping
+ * is, so that we can avoid repeated get_blocks calls.
+ *
+ * If the mapping spans EOF, then we have to break the mapping up as the mapping
+ * for blocks beyond EOF must be marked new so that sub block regions can be
+ * correctly zeroed. We can't do this for mappings within EOF unless the mapping
+ * was just allocated or is unwritten, otherwise the callers would overwrite
+ * existing data with zeros. Hence we have to split the mapping into a range up
+ * to and including EOF, and a second mapping for beyond EOF.
+ */
+static void
+xfs_map_trim_size(
+ struct inode *inode,
+ sector_t iblock,
+ struct buffer_head *bh_result,
+ struct xfs_bmbt_irec *imap,
+ xfs_off_t offset,
+ ssize_t size)
+{
+ xfs_off_t mapping_size;
+
+ mapping_size = imap->br_startoff + imap->br_blockcount - iblock;
+ mapping_size <<= inode->i_blkbits;
+
+ ASSERT(mapping_size > 0);
+ if (mapping_size > size)
+ mapping_size = size;
+ if (offset < i_size_read(inode) &&
+ offset + mapping_size >= i_size_read(inode)) {
+ /* limit mapping to block that spans EOF */
+ mapping_size = roundup_64(i_size_read(inode) - offset,
+ 1 << inode->i_blkbits);
+ }
+ if (mapping_size > LONG_MAX)
+ mapping_size = LONG_MAX;
+
+ bh_result->b_size = mapping_size;
+}
+
STATIC int
__xfs_get_blocks(
struct inode *inode,
xfs_iunlock(ip, lockmode);
}
-
- trace_xfs_get_blocks_alloc(ip, offset, size, 0, &imap);
+ trace_xfs_get_blocks_alloc(ip, offset, size,
+ ISUNWRITTEN(&imap) ? XFS_IO_UNWRITTEN
+ : XFS_IO_DELALLOC, &imap);
} else if (nimaps) {
- trace_xfs_get_blocks_found(ip, offset, size, 0, &imap);
+ trace_xfs_get_blocks_found(ip, offset, size,
+ ISUNWRITTEN(&imap) ? XFS_IO_UNWRITTEN
+ : XFS_IO_OVERWRITE, &imap);
xfs_iunlock(ip, lockmode);
} else {
trace_xfs_get_blocks_notfound(ip, offset, size);
goto out_unlock;
}
+ /* trim mapping down to size requested */
+ if (direct || size > (1 << inode->i_blkbits))
+ xfs_map_trim_size(inode, iblock, bh_result,
+ &imap, offset, size);
+
+ /*
+ * For unwritten extents do not report a disk address in the buffered
+ * read case (treat as if we're reading into a hole).
+ */
if (imap.br_startblock != HOLESTARTBLOCK &&
- imap.br_startblock != DELAYSTARTBLOCK) {
- /*
- * For unwritten extents do not report a disk address on
- * the read case (treat as if we're reading into a hole).
- */
- if (create || !ISUNWRITTEN(&imap))
- xfs_map_buffer(inode, bh_result, &imap, offset);
- if (create && ISUNWRITTEN(&imap)) {
- if (direct) {
- bh_result->b_private = inode;
- set_buffer_defer_completion(bh_result);
- }
+ imap.br_startblock != DELAYSTARTBLOCK &&
+ (create || !ISUNWRITTEN(&imap))) {
+ xfs_map_buffer(inode, bh_result, &imap, offset);
+ if (ISUNWRITTEN(&imap))
set_buffer_unwritten(bh_result);
- }
+ /* direct IO needs special help */
+ if (create && direct)
+ xfs_map_direct(inode, bh_result, &imap, offset);
}
/*
}
}
- /*
- * If this is O_DIRECT or the mpage code calling tell them how large
- * the mapping is, so that we can avoid repeated get_blocks calls.
- *
- * If the mapping spans EOF, then we have to break the mapping up as the
- * mapping for blocks beyond EOF must be marked new so that sub block
- * regions can be correctly zeroed. We can't do this for mappings within
- * EOF unless the mapping was just allocated or is unwritten, otherwise
- * the callers would overwrite existing data with zeros. Hence we have
- * to split the mapping into a range up to and including EOF, and a
- * second mapping for beyond EOF.
- */
- if (direct || size > (1 << inode->i_blkbits)) {
- xfs_off_t mapping_size;
-
- mapping_size = imap.br_startoff + imap.br_blockcount - iblock;
- mapping_size <<= inode->i_blkbits;
-
- ASSERT(mapping_size > 0);
- if (mapping_size > size)
- mapping_size = size;
- if (offset < i_size_read(inode) &&
- offset + mapping_size >= i_size_read(inode)) {
- /* limit mapping to block that spans EOF */
- mapping_size = roundup_64(i_size_read(inode) - offset,
- 1 << inode->i_blkbits);
- }
- if (mapping_size > LONG_MAX)
- mapping_size = LONG_MAX;
-
- bh_result->b_size = mapping_size;
- }
-
return 0;
out_unlock:
/*
* Complete a direct I/O write request.
*
- * If the private argument is non-NULL __xfs_get_blocks signals us that we
- * need to issue a transaction to convert the range from unwritten to written
- * extents.
+ * The ioend structure is passed from __xfs_get_blocks() to tell us what to do.
+ * If no ioend exists (i.e. @private == NULL) then the write IO is an overwrite
+ * wholly within the EOF and so there is nothing for us to do. Note that in this
+ * case the completion can be called in interrupt context, whereas if we have an
+ * ioend we will always be called in task context (i.e. from a workqueue).
*/
STATIC void
xfs_end_io_direct_write(
struct inode *inode = file_inode(iocb->ki_filp);
struct xfs_inode *ip = XFS_I(inode);
struct xfs_mount *mp = ip->i_mount;
+ struct xfs_ioend *ioend = private;
- if (XFS_FORCED_SHUTDOWN(mp))
+ trace_xfs_gbmap_direct_endio(ip, offset, size,
+ ioend ? ioend->io_type : 0, NULL);
+
+ if (!ioend) {
+ ASSERT(offset + size <= i_size_read(inode));
return;
+ }
+
+ if (XFS_FORCED_SHUTDOWN(mp))
+ goto out_end_io;
/*
- * While the generic direct I/O code updates the inode size, it does
- * so only after the end_io handler is called, which means our
- * end_io handler thinks the on-disk size is outside the in-core
- * size. To prevent this just update it a little bit earlier here.
+ * dio completion end_io functions are only called on writes if more
+ * than 0 bytes was written.
*/
+ ASSERT(size > 0);
+
+ /*
+ * The ioend only maps whole blocks, while the IO may be sector aligned.
+ * Hence the ioend offset/size may not match the IO offset/size exactly.
+ * Because we don't map overwrites within EOF into the ioend, the offset
+ * may not match, but only if the endio spans EOF. Either way, write
+ * the IO sizes into the ioend so that completion processing does the
+ * right thing.
+ */
+ ASSERT(offset + size <= ioend->io_offset + ioend->io_size);
+ ioend->io_size = size;
+ ioend->io_offset = offset;
+
+ /*
+ * The ioend tells us whether we are doing unwritten extent conversion
+ * or an append transaction that updates the on-disk file size. These
+ * cases are the only cases where we should *potentially* be needing
+ * to update the VFS inode size.
+ *
+ * We need to update the in-core inode size here so that we don't end up
+ * with the on-disk inode size being outside the in-core inode size. We
+ * have no other method of updating EOF for AIO, so always do it here
+ * if necessary.
+ *
+ * We need to lock the test/set EOF update as we can be racing with
+ * other IO completions here to update the EOF. Failing to serialise
+ * here can result in EOF moving backwards and Bad Things Happen when
+ * that occurs.
+ */
+ spin_lock(&ip->i_flags_lock);
if (offset + size > i_size_read(inode))
i_size_write(inode, offset + size);
+ spin_unlock(&ip->i_flags_lock);
/*
- * For direct I/O we do not know if we need to allocate blocks or not,
- * so we can't preallocate an append transaction, as that results in
- * nested reservations and log space deadlocks. Hence allocate the
- * transaction here. While this is sub-optimal and can block IO
- * completion for some time, we're stuck with doing it this way until
- * we can pass the ioend to the direct IO allocation callbacks and
- * avoid nesting that way.
+ * If we are doing an append IO that needs to update the EOF on disk,
+ * do the transaction reserve now so we can use common end io
+ * processing. Stashing the error (if there is one) in the ioend will
+ * result in the ioend processing passing on the error if it is
+ * possible as we can't return it from here.
*/
- if (private && size > 0) {
- xfs_iomap_write_unwritten(ip, offset, size);
- } else if (offset + size > ip->i_d.di_size) {
- struct xfs_trans *tp;
- int error;
-
- tp = xfs_trans_alloc(mp, XFS_TRANS_FSYNC_TS);
- error = xfs_trans_reserve(tp, &M_RES(mp)->tr_fsyncts, 0, 0);
- if (error) {
- xfs_trans_cancel(tp, 0);
- return;
- }
+ if (ioend->io_type == XFS_IO_OVERWRITE)
+ ioend->io_error = xfs_setfilesize_trans_alloc(ioend);
- xfs_setfilesize(ip, tp, offset, size);
- }
+out_end_io:
+ xfs_end_io(&ioend->io_work);
+ return;
}
STATIC ssize_t
git.openpandora.org / pandora-kernel.git / blobdiff