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Fix mmap / libaio deadlock

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Calling uiomove() in mappedread() under the page lock can result
in a deadlock if the user space page needs to be faulted in.

Resolve the issue by dropping the page lock before the uiomove().
The inode range lock protects against concurrent updates via
zfs_read() and zfs_write().

Reviewed-by: Albert Lee <trisk@forkgnu.org>
Reviewed-by: Chunwei Chen <david.chen@nutanix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #7335 
Closes #7339
This commit is contained in:
Brian Behlendorf
2018-03-28 10:19:22 -07:00
committed by GitHub
parent 668173b576
commit b2ab468dde
14 changed files with 184 additions and 5 deletions
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module/zfs/zfs_vnops.c
+1 -1
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@@ -400,6 +400,7 @@ mappedread(struct inode *ip, int nbytes, uio_t *uio)
pp = find_lock_page(mp, start >> PAGE_SHIFT);
if (pp) {
ASSERT(PageUptodate(pp));
unlock_page(pp);
pb = kmap(pp);
error = uiomove(pb + off, bytes, UIO_READ, uio);
@@ -409,7 +410,6 @@ mappedread(struct inode *ip, int nbytes, uio_t *uio)
flush_dcache_page(pp);
mark_page_accessed(pp);
unlock_page(pp);
put_page(pp);
} else {
error = dmu_read_uio_dbuf(sa_get_db(zp->z_sa_hdl),