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Revert "gfs2: Fix mmap locking for write faults" 

This reverts commit b7f55d928e.

As explained by Linus in [*], write faults on a mmap region are reads
from a filesysten point of view, so taking the inode glock exclusively
on write faults is incorrect.

Instead, when a page is marked writable, the .page_mkwrite vm operation
will be called, which is where the exclusive lock taking needs to
happen.  I got this wrong because of a broken test case that made me
believe .page_mkwrite isn't getting called when it actually is.

[*] https://lore.kernel.org/lkml/CAHk-=wj8EWr_D65i4oRSj2FTbrc6RdNydNNCGxeabRnwtoU=3Q@mail.gmail.com/

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Andreas Gruenbacher 2021-06-01 22:53:27 +02:00
parent c2131f7e73
commit d5b8145455
1 changed files with 1 additions and 3 deletions
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4
fs/gfs2/file.c
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@ -540,11 +540,9 @@ static vm_fault_t gfs2_fault(struct vm_fault *vmf)
struct gfs2_inode *ip = GFS2_I(inode);
struct gfs2_holder gh;
vm_fault_t ret;
u16 state;
int err;
state = (vmf->flags & FAULT_FLAG_WRITE) ? LM_ST_EXCLUSIVE : LM_ST_SHARED;
gfs2_holder_init(ip->i_gl, state, 0, &gh);
gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
err = gfs2_glock_nq(&gh);
if (err) {
ret = block_page_mkwrite_return(err);