On 9/21/20 10:43 AM, Goldwyn Rodrigues wrote:
From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
btrfs_write_check() checks for all parameters in one place before
beginning a write. This does away with inode_unlock() after every check.
In the later patches, it will help push inode_lock/unlock() in buffered
and direct write functions respectively.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
---
fs/btrfs/file.c | 159 ++++++++++++++++++++++++------------------------
1 file changed, 81 insertions(+), 78 deletions(-)
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index ca374cb5ffc9..0f961ce1fa98 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1615,6 +1615,85 @@ void btrfs_check_nocow_unlock(struct btrfs_inode *inode)
btrfs_drew_write_unlock(&inode->root->snapshot_lock);
}
+static void update_time_for_write(struct inode *inode)
+{
+ struct timespec64 now;
+
+ if (IS_NOCMTIME(inode))
+ return;
+
+ now = current_time(inode);
+ if (!timespec64_equal(&inode->i_mtime, &now))
+ inode->i_mtime = now;
+
+ if (!timespec64_equal(&inode->i_ctime, &now))
+ inode->i_ctime = now;
+
+ if (IS_I_VERSION(inode))
+ inode_inc_iversion(inode);
+}
+
+static size_t btrfs_write_check(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct file *file = iocb->ki_filp;
+ struct inode *inode = file_inode(file);
+ struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+ loff_t pos = iocb->ki_pos;
+ size_t count = iov_iter_count(from);
+ int err;
+ loff_t oldsize;
+ loff_t start_pos;
+
+ err = generic_write_checks(iocb, from);
+ if (err <= 0)
+ return err;
+
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ size_t nocow_bytes = count;
+
+ /*
+ * We will allocate space in case nodatacow is not set,
+ * so bail
+ */
+ if (check_nocow_nolock(BTRFS_I(inode), pos, &nocow_bytes)
+ <= 0)
+ return -EAGAIN;
+ /*
+ * There are holes in the range or parts of the range that must
+ * be COWed (shared extents, RO block groups, etc), so just bail
+ * out.
+ */
+ if (nocow_bytes < count)
+ return -EAGAIN;
+ }
+
+ current->backing_dev_info = inode_to_bdi(inode);
+ err = file_remove_privs(file);
+ if (err)
+ return err;
+
+ /*
+ * We reserve space for updating the inode when we reserve space for the
+ * extent we are going to write, so we will enospc out there. We don't
+ * need to start yet another transaction to update the inode as we will
+ * update the inode when we finish writing whatever data we write.
+ */
+ update_time_for_write(inode);
+
+ start_pos = round_down(pos, fs_info->sectorsize);
+ oldsize = i_size_read(inode);
+ if (start_pos > oldsize) {
+ /* Expand hole size to cover write data, preventing empty gap */
+ loff_t end_pos = round_up(pos + count,
+ fs_info->sectorsize);
+ err = btrfs_cont_expand(inode, oldsize, end_pos);
+ if (err)
+ return err;
In this case we're not re-setting current->backing_dev_info to NULL. Thanks,
Josef
