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
......@@ -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
......
......@@ -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 @@ skip_lock:
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);
......
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