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CIFS: Fix a deadlock when a file is reopened
If we request reading or writing on a file that needs to be reopened, it causes the deadlock: we are already holding rw semaphore for reading and then we try to acquire it for writing in cifs_relock_file. Fix this by acquiring the semaphore for reading in cifs_relock_file due to we don't make any changes in locks and don't need a write access. CC: <stable@vger.kernel.org> Signed-off-by: Pavel Shilovsky <pshilovsky@samba.org> Acked-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Steve French <smfrench@gmail.com>
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@ -561,11 +561,10 @@ cifs_relock_file(struct cifsFileInfo *cfile)
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struct cifs_tcon *tcon = tlink_tcon(cfile->tlink);
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int rc = 0;
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/* we are going to update can_cache_brlcks here - need a write access */
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down_write(&cinode->lock_sem);
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down_read(&cinode->lock_sem);
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if (cinode->can_cache_brlcks) {
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/* can cache locks - no need to push them */
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up_write(&cinode->lock_sem);
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/* can cache locks - no need to relock */
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up_read(&cinode->lock_sem);
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return rc;
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}
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@ -576,7 +575,7 @@ cifs_relock_file(struct cifsFileInfo *cfile)
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else
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rc = tcon->ses->server->ops->push_mand_locks(cfile);
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up_write(&cinode->lock_sem);
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up_read(&cinode->lock_sem);
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return rc;
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}
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