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Commit 2ca99501 authored by Steven Whitehouse's avatar Steven Whitehouse
Browse files

[GFS2] Fix page lock/glock deadlock 



This fixes a race between the glock and the page lock encountered
during truncate in gfs2_readpage and gfs2_prepare_write. The gfs2_readpages
function doesn't need the same fix since it only uses a try lock anyway, so
it will fail back to gfs2_readpage in the case of a potential deadlock.

This bug was spotted by Russell Cattelan.

Cc: Russell Cattelan <cattelan@redhat.com>
Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
parent c594d886

fs/gfs2/glock.h

+0 −1
Original line number Diff line number Diff line
@@ -27,7 +27,6 @@ 
#define GL_ATIME		0x00000200

#define GL_NOCACHE		0x00000400

#define GL_NOCANCEL		0x00001000

#define GL_AOP			0x00004000



#define GLR_TRYFAILED		13

#define GLR_CANCELED		14

fs/gfs2/ops_address.c

+9 −4
Original line number Diff line number Diff line
@@ -230,7 +230,7 @@ static int gfs2_readpage(struct file *file, struct page *page) 
				/* gfs2_sharewrite_nopage has grabbed the ip->i_gl already */

				goto skip_lock;

		}

		gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME|GL_AOP, &gh);

		gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME|LM_FLAG_TRY_1CB, &gh);

		do_unlock = 1;

		error = gfs2_glock_nq_m_atime(1, &gh);

		if (unlikely(error))
@@ -254,6 +254,8 @@ static int gfs2_readpage(struct file *file, struct page *page) 
out:

	return error;

out_unlock:

	if (error == GLR_TRYFAILED)

		error = AOP_TRUNCATED_PAGE;

	unlock_page(page);

	if (do_unlock)

		gfs2_holder_uninit(&gh);
@@ -293,7 +295,7 @@ static int gfs2_readpages(struct file *file, struct address_space *mapping, 
				goto skip_lock;

		}

		gfs2_holder_init(ip->i_gl, LM_ST_SHARED,

				 LM_FLAG_TRY_1CB|GL_ATIME|GL_AOP, &gh);

				 LM_FLAG_TRY_1CB|GL_ATIME, &gh);

		do_unlock = 1;

		ret = gfs2_glock_nq_m_atime(1, &gh);

		if (ret == GLR_TRYFAILED)
@@ -366,10 +368,13 @@ static int gfs2_prepare_write(struct file *file, struct page *page, 
	unsigned int write_len = to - from;





	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, GL_ATIME|GL_AOP, &ip->i_gh);

	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, GL_ATIME|LM_FLAG_TRY_1CB, &ip->i_gh);

	error = gfs2_glock_nq_m_atime(1, &ip->i_gh);

	if (error)

	if (unlikely(error)) {

		if (error == GLR_TRYFAILED)

			error = AOP_TRUNCATED_PAGE;

		goto out_uninit;

	}



	gfs2_write_calc_reserv(ip, write_len, &data_blocks, &ind_blocks);