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gfs2: Fix gfs2_release for non-writers regression

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When a file is opened for writing, the vfs code (do_dentry_open)
calls get_write_access for the inode, thus incrementing the inode's write
count. That writer normally then creates a multi-block reservation for
the inode (i_res) that can be re-used by other writers, which speeds up
writes for applications that stupidly loop on open/write/close.
When the writes are all done, the multi-block reservation should be
deleted when the file is closed by the last "writer."

Commit 0ec9b9ea4f broke that concept when it moved the call to
gfs2_rs_delete before the check for FMODE_WRITE.  Non-writers have no
business removing the multi-block reservations of writers. In fact, if
someone opens and closes the file for RO while a writer has a
multi-block reservation, the RO closer will delete the reservation
midway through the write, and this results in:

kernel BUG at fs/gfs2/rgrp.c:677! (or thereabouts) which is:
BUG_ON(rs->rs_requested); from function gfs2_rs_deltree.

This patch moves the check back inside the check for FMODE_WRITE.

Fixes: 0ec9b9ea4f ("gfs2: Check for active reservation in gfs2_release")
Cc: stable@vger.kernel.org # v5.12+
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Bob Peterson 2022-01-18 09:30:18 -05:00 committed by Andreas Gruenbacher
parent 356b8103d4
commit d3add1a951
1 changed files with 4 additions and 3 deletions
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7
fs/gfs2/file.c
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@ -704,10 +704,11 @@ static int gfs2_release(struct inode *inode, struct file *file)
kfree(file->private_data);
file->private_data = NULL;
if (gfs2_rs_active(&ip->i_res))
gfs2_rs_delete(ip, &inode->i_writecount);
if (file->f_mode & FMODE_WRITE)
if (file->f_mode & FMODE_WRITE) {
if (gfs2_rs_active(&ip->i_res))
gfs2_rs_delete(ip, &inode->i_writecount);
gfs2_qa_put(ip);
}
return 0;
}