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Fix errant EFAULT during writes (#8719)

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Commit 98bb45e resolved a deadlock which could occur when
handling a page fault in zfs_write().  This change added
the uio_fault_disable field to the uio structure but failed
to initialize it to B_FALSE.  This uninitialized field would
cause uiomove_iov() to call __copy_from_user_inatomic()
instead of copy_from_user() resulting in unexpected EFAULTs.

Resolve the issue by fully initializing the uio, and clearing
the uio_fault_disable flags after it's used in zfs_write().

Additionally, reorder the uio_t field assignments to match
the order the fields are declared in the  structure.

Reviewed-by: Chunwei Chen <tuxoko@gmail.com>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #8640 
Closes #8719
This commit is contained in:
Brian Behlendorf
2019-05-08 10:04:04 -07:00
committed by GitHub
parent 1f02ecc5a5
commit 515ddf6504
4 changed files with 16 additions and 16 deletions
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module/zfs/zfs_vnops.c
+1
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@@ -822,6 +822,7 @@ zfs_write(struct inode *ip, uio_t *uio, int ioflag, cred_t *cr)
uio->uio_fault_disable = B_TRUE;
error = dmu_write_uio_dbuf(sa_get_db(zp->z_sa_hdl),
uio, nbytes, tx);
uio->uio_fault_disable = B_FALSE;
if (error == EFAULT) {
dmu_tx_commit(tx);
if (uio_prefaultpages(MIN(n, max_blksz), uio)) {