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gfs2: fiemap page fault fix

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In gfs2_fiemap(), we are calling iomap_fiemap() while holding the inode
glock.  This can lead to recursive glock taking if the fiemap buffer is
memory mapped to the same inode and accessing it triggers a page fault.

Fix by disabling page faults for iomap_fiemap() and faulting in the
buffer by hand if necessary.

Fixes xfstest generic/742.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Andreas Gruenbacher
2026-02-05 15:52:57 +01:00
parent da6f5bbc2e
commit e411d74cc5
1 changed files with 16 additions and 0 deletions
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16
fs/gfs2/inode.c
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@@ -2192,6 +2192,14 @@ static int gfs2_getattr(struct mnt_idmap *idmap,
return 0;
}
static bool fault_in_fiemap(struct fiemap_extent_info *fi)
{
struct fiemap_extent __user *dest = fi->fi_extents_start;
size_t size = sizeof(*dest) * fi->fi_extents_max;
return fault_in_safe_writeable((char __user *)dest, size) == 0;
}
static int gfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
u64 start, u64 len)
{
@@ -2201,14 +2209,22 @@ static int gfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
inode_lock_shared(inode);
retry:
ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
if (ret)
goto out;
pagefault_disable();
ret = iomap_fiemap(inode, fieinfo, start, len, &gfs2_iomap_ops);
pagefault_enable();
gfs2_glock_dq_uninit(&gh);
if (ret == -EFAULT && fault_in_fiemap(fieinfo)) {
fieinfo->fi_extents_mapped = 0;
goto retry;
}
out:
inode_unlock_shared(inode);
return ret;